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Abstract
Large-scale shaking table test was performed to study dynamic response characters and failure mechanism of rock slopes triggered by Wenchuan earthquake. Sine waves with different frequencies, amplitudes and duration times were mainly input. Testing results show that: acceleration amplification coefficients increased nonlinearly with the increasing elevation, and they almost reach to maximum at slope surface and shoulder. Horizontal acceleration is amplified more obvious than vertical acceleration at top part of slope (above three-quarters of slope height) which is the opposite at the lower part. Acceleration amplification coefficients increased with the increasing seismic frequency nonlinearly; distribution of acceleration in slope body changed with variation of frequency. Once the input frequency approximated to the natural frequency of model slope, dynamic acceleration is amplified most obviously. Acceleration amplification coefficients increased with the increment of seismic wave amplitude; but amplitude doesn't change the distribution of acceleration in slope body. Duration time of seismic wave has little influence on dynamic characters. Slope structure controls the deformation modes of rock slope; and acceleration amplification coefficients of bedding slope are about 15% more than those of the homogeneous slope, because of a large amount of structural surfaces in bedding slope which can make propagation of seismic wave more complex.
... Furthermore, cracking, dislocation and faulting are caused by seismic loading on mudded intercalations as well (shown in Fig. 1), which are correlated to the fatigue damage effect actually. (Dong et al., 2010;Tang et al., 2019;Yang et al., 2012). ...
... The previous researches usually simplified the seismic loading to a cyclic dynamic loading, which is simulated by equivalent sine wave (Dong et al., 2010;Yang et al., 2012). However, only a few studies have been focused on the dynamic response of mudded intercalations (Xue and Wang, 1997;Yan et al., 2018). ...
... Assuming that there is a strain-hardening parameter, h, corresponding to a material parameter of mudded intercalations related to cumulative plastic strain ε p , h can be expressed as a function of Δσ d and N: (Yang et al., 2012). ...
Fatigue damage caused by cyclic dynamic loading may deteriorate strength parameters of mudded intercalations. This research work aimed at defining a new fatigue damage variable expression and revealing the fatigue damage evolution laws of mudded intercalations by conducting dynamic triaxial tests. The specimens were collected in China and remodeled. The test results indicated that the dynamic stress-strain curves of mudded intercalations represented obvious strain-hardening characteristics. The new fatigue damage variable expression was formulated according to Ramberg-Osgood strain-hardening law applied to a three-direction stress state. The fatigue damage evolution laws of mudded intercalations could be described by a low-cycle damage evolution model and could be aligned with dynamic strength failure laws. The fatigue damage deepened with an increase in the cyclic ratio. The fatigue damage evolution rate was correlated with the clay mineral composition and percent of clay size particles (strongly), water content (moderately positive), confining pressure (weakly positive), and the cyclic ratio (initially, negative and then, positive).
... The characteristics of displacements at the surface and top of the slope conform to the failure mode of slope with the moisture content of 12.5% (shatter-breakdown landslide). Figure 20 shows a comparison between the results obtained in this work and those reported in previous studies (Dong et al., 2011;Yang et al., 2012). The relationship between AFA and relative elevation in the present study agrees well with the ones reported in previous studies. ...
... The relationship between AFA and relative elevation in the present study agrees well with the ones reported in previous studies. Figure 21 presents a comparison of AFA with the increase in EFA between the present results and those reported by Dong et al. (2011) and Yang et al. (2012). The results obtained in this work are mainly for low EFA (1-6 Hz), whereas those by Dong et al. (2011) and Yang et al. (2012) are for higher EFA (5-20 Hz). ...
... Figure 21 presents a comparison of AFA with the increase in EFA between the present results and those reported by Dong et al. (2011) and Yang et al. (2012). The results obtained in this work are mainly for low EFA (1-6 Hz), whereas those by Dong et al. (2011) and Yang et al. (2012) are for higher EFA (5-20 Hz). EFA at low frequency excites a lower AFA, whereas EFA at high frequency triggers a higher AFA, as shown in Figure 21. ...
Understanding the relationship between the moisture content of unsaturated soil and the instability and dynamic response of slope under the action of seismic load can bring convenience to the field of slope safety assessment. The effect of moisture content of the unsaturated soil on the failure mode and dynamic response of slope under seismic loading was investigated using shaking table tests. In this regard, three different moisture contents of 5%, 8.1%, and 12.5% were considered. The experimental results show that the amplification factor of acceleration (AFA) on the slope surface increases with the increase in both relative elevation and excitation amplitude of acceleration (EAA). As the moisture content of unsaturated soil increases, AFA tends to decrease. An empirical correlation describing the relationship among AFA, relative elevation, dimensionless EAA, and moisture content of unsaturated soil was proposed. The excitation frequency of acceleration (EFA) has a significant impact on the AFA at the middle and upper parts of the slope. The deformation of slope surface is able to reflect the failure mode of slope, which can be used in slope monitoring work. The slope with different moisture contents of unsaturated soil has different instability modes. With the increase in soil moisture content, the slope needs more energy to reach the unstable state under seismic loading. There are three typical regions of principal stress field in the slope exposed to seismic loading, which control the evolution of initial slip plane inside the slope.
... For instance, the AFAs in the result of Fan et al. (2016) vary slightly along the elevation of slope, which are smaller than those by present study, Liu & Xu (2014), Xu et al. (2008) and Chen et al. (2010). Figure 9b presents the comparison of AFAs with increasing EFAs between present study and those by Dong et al. (2011), Xu et al. (2008, Yang et al. (2012) and Srilatha et al. (2013), and the detailed test parameters are listed in Table 6. It can be seen from the figure that the results by present study, Xu et al. (2008) and Srilatha et al. (2013) mainly give the results at low EFA (1-6 Hz), and those by Dong et al. (2011) and Yang et al. (2012) mainly present the results at high EFA (5-20Hz). ...
... Figure 9b presents the comparison of AFAs with increasing EFAs between present study and those by Dong et al. (2011), Xu et al. (2008, Yang et al. (2012) and Srilatha et al. (2013), and the detailed test parameters are listed in Table 6. It can be seen from the figure that the results by present study, Xu et al. (2008) and Srilatha et al. (2013) mainly give the results at low EFA (1-6 Hz), and those by Dong et al. (2011) and Yang et al. (2012) mainly present the results at high EFA (5-20Hz). As a whole, EFA at low frequency triggers a lower AFA, and EFA at high frequency induces a higher AFA, as indicated in Figure 10. ...
... As a whole, EFA at low frequency triggers a lower AFA, and EFA at high frequency induces a higher AFA, as indicated in Figure 10. It is also seen from the figure that the results by present results, Xu et al. (2008) and Srilatha et al. (2013) and those by Dong et al. (2011) and Yang et al. (2012) are almost harmonious, and both of them give a relatively complete curve about variation of AFA with EFA from 1Hz to 20Hz. ...
A double-sided slope with high water content in sandy clay was considered under the action of seismic load. Its failure mode and dynamic response were investigated using a hydraulic servo shaking table test. The typical characteristic of failure mode and dynamic responses of the double-sided slope were analyzed. Experimental results show that slope failure undergoes a process of progressive deformation. The slope failure mode can be explained as creep sliding landslide. AFA (Amplification Factor of Acceleration) at the surface and inner parts of the slope shows an increasing trend with the increase of relative elevation. The relationship between AFA and EAA (Excitation Amplitude of Acceleration) is nonlinear. An empirical formula is proposed to describe preferably the relationship between AFA, relative elevation and dimensionless EAA. The AFA at the middle and upper parts of the slope increases apparently with increasing EFA (Excitation Frequency of Acceleration).
... The PGA amplification factors with 4.47 scaled El Centro earthquake record input were greater than that with full El Centro earthquake record excitation (Chen et al. 2010). Shaking table tests results also revealed that the closer the excitation frequency is to the resonance frequency of the slope, the greater the PGA amplification factor, and the input frequency had a great influence on the PGA distribution in bedding rock slope and anti-dip rock slope (Dong et al. 2011;Yang et al. 2012aYang et al. , 2018b. The seismic amplification effect on the slope surface increased with the increase in the predominant frequency of input seismic wave, and meanwhile the acceleration amplification factor at the slope surface decreased when the amplitude was greater than 0.3 g (Fan et al. 2015(Fan et al. , 2016. ...
... The velocity of shear wave propagation through the medium (C s ) is assumed based on description of the material when the parameter is not presented in references. Hence, results of previous studies (Chen et al. 2010;Dong et al. 2011;Fan et al. 2015Fan et al. , 2016Lin and Wang 2006;Liu et al. 2014;Wang 2006;Xu et al. 2008;Yang et al. 2018aYang et al. , 2012aZhao et al. 2015) and current study are shown in Fig. 13. It can be found that acceleration amplification factor at the crest of the slope increases first and then it shows a decrease tendency with the increasing H/λ, and the turning value of H/λ is around 0.2 which is also consistent with the numerical simulation results (Ashford et al. 1997;Bouckovalas and Papadimitriou 2005;Qi 2006). ...
This paper studied the dynamic response of the homogeneous step-like rock slope under wide frequency and amplitude through a large-scale shaking table test. A homogenous rock slope with a length of 3.50 m, width of 0.68 m and height of 1.20 m was constructed in a rigid steel box. Results indicate that acceleration amplification factor in horizontal direction (AAF-X) along the slope surface is amplified with the increase in the slope height when loading frequency ≤ 45 Hz, while AAF-X decreases first then increases when loading frequency is 60 Hz and 75 Hz. The acceleration amplification factor in vertical direction (AAF-Z) increases first and then decreases with the increase in the slope height. The resonance frequency of slope near the slope crest decreases from 61.37 to 58.12 Hz, while the damping ratio increases from 5.8 to 8.8%, as the loading amplitude increases from 0.1 to 0.5 g. The AAF reminds linear increase with a loading amplitude of up to 0.4 g while decreases when the loading amplitude becomes larger than 0.5 g. It reveals that the loading amplitude has a “double-effect” on the seismic response of the homogeneous rock slope. That is, on the one hand, the larger the loading amplitude, the stronger the acceleration intensity, the greater deterioration of rock slope structure or material and the larger damping ratio of the slope; on the other hand, more energy will be dissipated due to plastic deformation or particle friction of high damping ratio and weaker slope structure. Such test result can be used for understanding the dynamic instability mechanism of the homogeneous slope in the field.
... In addition, a small number of rockfalls accumulated at the slope toe, as shown in Fig. 11c. These failure phenomena were consistent with the field investigation on coseismic landslides induced by the Wenchuan earthquake (Yang, 2011). (4) Stage IV. ...
... Fig. 13. Buckling of bedding slope due to the Wenchuan earthquake (Yang, 2011). ...
A B S T R A C T
Bedding rock slopes are common geological features in nature that are prone to failure under strong earthquakes. Their failures induce catastrophic landslides and form barrier lakes, posing severe threats to people's lives and property. Based on the similarity criteria, a bedding rock slope model with a length of 3 m, a width of 0.8 m, and a height of 1.6 m was constructed to facilitate large-scale shaking table tests. The results showed that with the increase of vibration time, the natural frequency of the model slope decreased, but the damping ratio increased. Damage to the rock mass structure altered the dynamic characteristics of the slope; therefore, amplification of the acceleration was found to be nonlinear and uneven. Furthermore, the acceleration was amplified nonlinearly with the increase of slope elevation along the slope surface and the vertical section, and the maximum acceleration amplification factor (AAF) occurred at the slope crest. Before visible deformation, the AAF increased with increasing shaking intensity; however, it decreased with increasing shaking intensity after obvious deformation. The slope was likely to slide along the bedding planes at a shallow depth below the slope surface. The upper part of the slope mainly experienced a tensile-shear effect, whereas the lower part suffered a compressive-shear force. The progressive failure process of the model slope can be divided into four stages, and the dislocated rock mass can be summarized into three zones. The testing data provide a good explanation of the dynamic behavior of the rock slope when subjected to an earthquake and may serve as a helpful reference in implementing antiseismic measures for earthquake-induced landslides.
... The understanding of rock slope dynamic evolution is the design basis for landslide prevention and control. The failure mechanism and dynamic response characteristics of a rock slope are also the foundation for dynamic stability evaluation of the slope under seismic loading (Dong et al. 2011;Yang et al. 2012;Chang et al. 2021). A number of previous studies have aimed to analyze the dynamic response of rock slopes under earthquake motions and have achieved some important results. ...
... In shaking table tests, the response of the slope can be studied under different ground motion inputs and waveforms with varying model sizes. As a result, the dynamic response of the slope can be accurately obtained (Lin 2006;Yang 2012;Yang et al. 2018). Therefore, shaking table tests have become one of the best methods for studying rock slopes, and can reflect the dynamic response and failure modes of slopes under earthquake motions (Chen 2016;Fan et al. 2016a, b;Sun et al. 2019). ...
Under the impact of earthquake, even if the slopes do not fail, the integrity of rock slope structure would be damaged subjected to the seismic motion. The process of damage, destruction and failure for slopes is characterized by the dynamic evolution of stability. In the areas with active tectonic activities, frequent earthquakes have a significant effect on the attenuation of slope stability. To investigate the dynamic evolution of a rock slope under earthquake motions, a series of shaking table tests were performed. An artificial synthetic earthquake seismic wave was adopted to investigate the horizontal acceleration response. The results show that the wave field propagation results in acceleration amplification for the slope body above the tuff structural surface are larger than those inside the slope, and a maximum value of 3.7 is observed at slope crest. The structural surface results in a mutation of the acceleration response, which is not conducive to the slope stability. The modeled slope entered the plastic stage (input motion of 2.97 m/s2) earlier than landslides occurred (input motion of 4.46 m/s2). In addition, the safety factor of the sliding blocks was calculated based on pseudo static analysis. A good correspondence was found between the safety factors and the failure mode of the slope. The damage evolution process for the rock slope can be divided into three stages: an elastic stage (1.6 < safety factor ≤ 4.7), a plastic stage (0.8 < safety factor ≤ 1.6), and a damage stage (safety factor ≤ 0.8).
... However, with the increase of loading rate, the damage degree, failure mode, peak strength and deformation parameters of rock materials have nonlinear changes. Most of the similar relationships of dynamic parameters of current shaking table model tests (Zou et al., 2011;Yang et al., 2012;Ye et al., 2012a;Ye et al., 2012b;Huang et al., 2013;Hou, 2013;Li et al., 2014;Fan et al., 2015;Feng et al., 2018;Liu et al., 2019;Liu et al., 2020) are derived from static conditions of three basic physical quantities combined with dimensionality analysis and π determination, without sufficient consideration of dynamic factors. ...
It is very important to determine the dynamic similarity relation in the shaking table model test. The accurate dynamic similarity relation can make the model reflect the dynamic characteristics of the prototype to the greatest extent. This paper describes the principle of similarity design for shaking table model test and reviews the related literature. According to the different research objects and purposes, four common similarity design methods including separation similarity method, artificial mass method, less artificial mass method and ignoring gravity method are summarized. Analysis of the shortcomings of the method of deriving frequency compression ratio from static factors in the design of seismic wave similarity relation. The Duhamel integral analytic expression of the structure motion equation under earthquake is analyzed. The seismic response of the structure is closely related to the natural vibration frequency of the structure. A design method using frequency as input seismic wave similarity design control quantity is proposed. The natural vibration frequencies of the prototype and the model are studied by means of the Gonza landslide field ground pulsation test and the model white noise excitation. A new frequency compression ratio design scheme is given from the perspective of dynamic similarity. It is of great reference significance to optimize the dynamic similarity design of shaking table model test and improve the accuracy of test results.
... In shaking table tests, the response of the slope can be studied under different ground motion inputs and waveforms with varying model sizes. As a result, the dynamic response of the slope can be accurately obtained (Lin, 2006;Yang, 2012). Therefore, shaking table tests have become one of the best methods for studying rock slopes, and can re ect the dynamic response and failure modes of slopes under earthquake motions (Chen, 2016;Fan, 2016). ...
Under the impact of earthquake, even if the slopes do not fail, the integrity of rock slope structure would be damaged subjected to the seismic motion. The process of damage, destruction and failure for slopes is characterized by the dynamic evolution of stability. In the areas with active tectonic activities, frequent earthquakes have a significant effect on the attenuation of slope stability. To investigate the dynamic evolution of a rock slope under earthquake motions, a series of shaking table tests were performed. An artificial synthetic earthquake seismic wave was adopted to investigate the horizontal acceleration response. The results show that the wave field propagation results in M PGA values for the slope body above the tuff structural surface are larger than those inside the slope, and a maximum value of 3.7 is observed at slope crest. The structural surface results in a mutation of the acceleration response, which is not conducive to the slope stability. The modeled slope entered the plastic stage (input motion of 2.97 m/s ² ) earlier than landslides occurred (input motion of 4.46 m/s ² ). In addition, the safety factor of the sliding blocks was calculated based on pseudo static analysis. A good correspondence was found between the safety factors and the failure mode of the slope. The damage evolution process for the rock slope can be divided into three stages: an elastic stage (K s =1.6–4.7), a plastic stage (K s =0.8–1.6), and a damage stage (K s <0.8).
... In addition, in most cases of dynamic loads, such as vehicle load and seismic load, previous studies usually simplified them to cyclic dynamic loadings (Yang et al. 2012;Hussaini et al. 2015), which are simulated by equivalent sine waves. During cyclic dynamic loading, foamed concretes would produce cumulative deformation and fatigue damage (Xu et al. 2018). ...
To investigate the dynamic response of silt-based foamed concrete as filler in subgrade, this paper conducted staged cyclic loading experiments to examine its dynamic properties. Influence factors such as wet density and silt content were also addressed in experiments. The results of tests indicated that the hysteretic curves of silt-based foamed concrete presented obvious elastoplastic characteristics, and the dynamic stress-cumulative strain curves have a strain-hardening phenomenon. Dynamic strength increased a mean level of 65% when density increased by an average of 100 kg=m 3 at the range of density 600-800 kg=m 3. Meanwhile, the dynamic strength decreased by an average of 14.2% if silt content increased by a mean of 10%. Furthermore, the addition of silt transformed the pore structures from uniformly distributed sphericity into irregular combined bubbles with larger diameters. Besides, during the staged cyclic loading process, it was deduced that dynamic elastic modulus of material has a variation with cycles, but can be basically assumed constant in tests. Thus, the dynamic stress-cumulative strain curves of silt-based foamed concrete subjected to staged cyclic loads were derived based on the Ramberg-Osgood equation. The parameters of the Ramberg-Osgood equation were also analyzed according to the test data. Finally, the damage variable expressions versus plastic strain and cyclic numbers were established respectively. It was found that density and silt content can significantly affect damage evolution.
... It is appropriate for simulating the discontinuity behavior of engineered rock structures. Hence, the improvements and extensions of DDA have been extensively studied (Bao et al., 2012;Fan and He, 2015), and widely used in many aspects, such as landslide (Wu, 2010;Zhang et al., 2014), rockfall (Chen et al., 2013) and slope collapse (Yang et al., 2012). ...
The accurate consideration of seismic wave propagation through discontinuous media is crucial in rock engineering. Discontinuous deformation analysis (DDA), with the ability to study discontinuity behaviors, is modified by incorporating a seismic input method based on a viscous boundary and the free-field theory. After confirming the accuracy of the modified DDA using several verification examples, two practical applications, (1) the extreme ground motion during the 2008 Iwate–Miyagi earthquake, Japan, and (2) the Donghekou landslide induced by the 2008 Wenchuan earthquake, China, are simulated and reproduced by the modified DDA. The results show that seismic wave propagation through discontinuous media can be accurately simulated by the modified DDA. Further, the simulation results indicate that discontinuities are critical in the dynamic response of structures. Conclusively, the modified DDA provides an alternative approach for analyzing the dynamic response of sites containing discontinuities.
... In recent years, shaking table tests have been used to simulate the variation of dynamic response of rock slopes and directly reveal the failure modes of structure under seismic excitation Fan et al. 2016), allowing various types of lithology combinations and structures to be studied, in particular, slopes with discontinuous joints (Che et al. 2016) and slopes with weak intercalation Fan et al. 2016). In large-scale shaking table tests, the model size, the ground motion input parameters, and waveforms can be controlled based on the case studies to enable the slope dynamic responses to be measured to greater accuracy (Hong et al. 2005;Lin and Wang 2006;Lin et al. 2015;Yang et al. 2012). Therefore, the shaking table test method has been one direct way to simulate the variation of dynamic response of slope and directly reveal the failure modes of structure under seismic excitation Fan et al. 2016). ...
In order to study the dynamic response characteristics of a rock slope with discontinuities under the combined action of earthquakes and rapid water drawdown, a large-scale shaking table test was performed on a rock slope with discontinuous joints. Wenchuan earthquake (WE) seismic records were performed to investigate the horizontal and vertical acceleration response and displacement response. In particular, three-dimensional optical measurement techniques was used to obtain the slope surface displacements. A comparison was made on the seismic response according to the analysis of PGD (peak ground displacement) and MPGA (acceleration amplification coefficient) of the modeled slope. The results show that the experimental slope mainly underwent settlement and horizontal deformation when the WE records were applied in the z and x directions, respectively. The slope was first shaken by the P wave, which caused the differential settlement to occur at the surface slope; then, the slope was shaken more severely by the S wave, which led to a greater horizontal deformation. Moreover, analysis of the ΔPGD (increment of PGD) and ΔMPGA (increment of MPGA) under rapid drawdown suggests that the rapid water drawdown mainly impacts the deformation of the surface slope, particularly between the high and low water levels. The water infiltration through the cracks softened the material of the surface slope, and the rapid drawdown also enhanced the slope deformation. In addition, the damage evolution process of the slope can be identified, mainly including three stages: an elastic stage (< 0.168 g), a plastic stage (0.168–0.336 g), and a failure stage (> 0.336 g).
... The results also confirm the analyses of the 192 reports of underground construction destructions during earthquakes (Sharma and Judd 1991), as well as the failure types and characteristics of the mountain tunnels during the Wenchuan earthquake (Li 2008). Shaking table tests show that acceleration amplification coefficients increase nonlinearly with increasing elevations, and generally reach a maximum at the slope surface and on its shoulders (Yang et al. 2012). Our research results are also in agreement with Yang's results, and all reveal the dynamic response of the slope from the outside to the inside in their measured monitoring data and shaking table tests. ...
In order to investigate the role of the amplification of peak ground acceleration (PGA) in seismic landslide formation mechanisms and study how earthquake waves interact with rock structures, a few strong-motion seismometers are installed at various locations on both sides of the Lengzhuguan gully. Five strong-motion seismometers were triggered at different depths in a tunnel at the same altitude during the Kangding Ms 5.8 earthquake on November 25th, 2014. The data reveal that the horizontal peak acceleration (PGAH) at each site decreased with increasing site depths. The PGAH at the deepest monitoring site (99 m from the tunnel entrance) was approximately half that of the outermost site. The amplitude of the acceleration response spectrum was also attenuated from the entrance inwards, the dynamic magnification factor (β) of the standard acceleration spectrum was less than 3.5, and rate of change was the same as that for the amplitude acceleration response. The Fourier spectra of each monitoring site also decreased from the outside inwards, and the components of the Fourier spectra were more complex at the surface.
... Compared with previous results (Huang et al. 2013b), our findings show that the acceleration amplification coefficients of bedding and counter-bedding slope models with weak intercalated layers are larger than those without weak intercalated layers. Yang et al. (2012) pointed out that, owing to reflection and refraction by the layer surfaces, reflection and refraction waves would become superimposed in the slope, thus increasing the acceleration amplification coefficients as compared with a homogenous slope. ...
A large-scale shaking table test was performed to study the dynamic response of slopes parallel to geological bedding (bedding slopes) and slopes that cross-cut geological bedding (counter-bedding slopes). The test results show that the acceleration amplification coefficients increase with increasing elevation and, when the input earthquake amplitude is greater than 0.3 g, both bedding and counter-bedding slopes begin to show nonlinear dynamic response characteristics. With increasing elevation, the displacement of the bedding slope surface increases greatly. Conversely, the displacement of the counter-bedding slope surface increases first and then decreases; the slope develops a bulge at the relative elevation of 0.85. The displacement of the bedding slope surface is greater than that of the counter-bedding slope. The counter-bedding slope is more seismically stable compared with the bedding slope. Based on the Hilbert–Huang transform and marginal spectrum theories, the processes that develop dynamic damage of the bedding and counter-bedding slopes are identified. It is shown that the dynamic failure mode of the bedding slope is mainly represented by vertical tensile cracks at the rear of the slope, bedding slide of the strata along the weak intercalation, and rock collapse from the slope crest. However, the dynamic failure mode of the counter-bedding slope is mainly represented by staggered horizontal and vertical fissures, extrusion of the weak intercalation, and breakage at the slope crest.
... The results also confirm the analyses of the 192 reports of underground construction destructions during earthquakes (Sharma and Judd 1991), as well as the failure types and characteristics of the mountain tunnels during the Wenchuan earthquake (Li 2008). Shaking table tests show that acceleration amplification coefficients increase nonlinearly with increasing elevations, and generally reach a maximum at the slope surface and on its shoulders (Yang et al. 2012). Our research results are also in agreement with Yang's results, and all reveal the dynamic response of the slope from the outside to the inside in their measured monitoring data and shaking table tests. ...
In order to reveal the characteristics of the peak acceleration at different depths of a slope and seismic landslide formation mechanism, a strong earthquake monitoring array was set up in both sides of the Lengzhuguan slope. Five strong vibrograph at different depths but the same altitude were triggered by Kangding Ms 5.8 earthquake occurred on December 25th, 2014. The data reveals that the horizontal peak acceleration at each monitoring site decreases with the increase of depth. It decreases greatly within the surface range of 0 to 45 m and at the inner slope falls at a slow rate. At the monitoring site (99 m from the hole) the horizontal peak acceleration is about 0.6 times the one at the hole. The acceleration response spectrum shows that the amplitudes at monitoring sites decay with the increase of the depth, and the dynamic magnification factor β of standard spectra is less than 3.5. Fourier spectrum shows that the amplitudes also decrease gradually from the outside hole to the inside slope, and near the hole, the components of the spectrum become complex.
The geological structure and stratum lithology have important roles in the seismic stability of complex slopes; however, their roles complicate engineering construction. Four three-dimensional, layered granite slope models with infinite boundaries were modeled via the finite element method. The seismic response characteristics of slopes are systematically analyzed in the time–frequency domain. A frequency-domain analysis method of complex slopes, including modal and spectrum conjoint analysis, is proposed. Modal analysis can directly display the main vibration modes of slopes. The combination of modal and spectral analysis can clarify the inherent characteristics of slopes and reveal the interaction mechanism between the inherent frequency of slopes and their dynamic characteristics. The results illustrate that structural planes have significant effects on the propagation characteristics of waves within rock masses, and complex refraction/reflection phenomena occur near these discontinuities, thus leading to different dynamic response characteristics in the slope. Layered slopes have an apparent magnification effect of slope surface and altitude. The directions of seismic excitation and structural plane types affect the dynamic response of slopes. Horizontal waves mainly affect the middle and upper parts of high-steep slopes, while vertical waves have an obvious influence on the slope crest. Additionally, Fourier spectral analysis shows that structural planes have filtering effects on high-frequency waves. Combined with modal analysis, this finding further explains that the high-frequency section of waves mainly triggers local deformation of slopes, while the low-frequency component controls their overall deformation. The instability regions and evolution process of slopes were predicted based on time–frequency conjoint analysis.
Multi-tilted layered soil is widespread in the mountainous areas of China, and pile systems are widely applied to foundation support and repair. In order to investigate the seismic response of pile systems in multi-tilted layered soils under earthquake and rainfall, two models were built and tested through a large 1-g shaking table. The interlayer was tilted and highly weathered, and it was saturated during rainfall. The piles were embedded in the bedrock with different lengths. The results showed that: 1) The acceleration response was weakened in the interlayer, and it diminished as the earthquake amplitude increased. The structures showed the maximum acceleration response. 2) The existence of water in the tilted interlayer led to a greater response of the superstructure. The bending moment of piles varied under different containers, which was mainly due to the inertial force of the container and the potential sliding force of the covering layer. The water in the interlayer from rainfall promoted the bending moment caused by the potential sliding force, increasing the potential risk of instability of the system. 3) The motion mode of the container under rainfall was translation. The rotation angle of the container with saturated moisture content was significant and it increased with the increase of the earthquake amplitude.
A shaking table model test was conducted to study the dynamic response and failure mechanism of a bedding rock slope with weak rock layer based on the “Xiaguiwa” landslide in the Jinsha River basin of Sichuan-Tibet. The influence of schist-like weak rock layer on bedding rock slope is considered. The test results show that the Peak Ground Acceleration (PGA) amplification coefficient varies rhythmically from the inside to the surface of the slope, and 0.3 g and 0.6 g are the slope appears cracking and instability. schist-like weak rock layer makes the seismic wave enhance obviously, but in the slope flexure position, the seismic wave near the weak rock layer is slightly weakened instead, and the maximum displacement often occurs above the weak rock layer. the “bucking” occurs at 1/4 of the slope height, and the fracture degree at the middle and lower part of the slope is greater than that at the middle and upper part, and the slope damage surface appears to be “concave at the top and convex at the bottom”. The damage process of the model slope is divided into four stages. The model test results reflect the influence of the weak rock layer on the seismic dynamic response and damage process of the bedding rock slope.
Based on the two-dimensional discrete element software UDEC, this article studied the dynamic response laws of rock slopes with inverse nonpersistent joints by the combination of different dip angles and spacing of joint and length of rock bridge under earthquake. The results showed that the existence of the joint surface had a significant impact on the dynamic response of the slope. When the dip angle of inverse nonpersistent joint increases or the joint spacing decreases, the PGA amplification factor of each monitoring point on the slope surface increases, and the influence range is mainly concentrated in the middle of the slope surface to the slope shoulder. Along the horizontal direction of the slope, closer to the shoulder of the slope, the PGA amplification factor increases with the increase of the joint dip angle and the decrease of rock bridge length and joint spacing; along the vertical direction, the PGA amplification coefficient curve increases first, then decreases, and then increases with the change of elevation, and the dynamic response of slope reacts the most violent where the joints are densely developed.
China is located at the intersection of the Pacific Rim and Eurasian seismic belts. The compression and tension between plates have caused the development of fault zones. High frequency, wide distribution, and strong activity have become the main characteristics of China’s seismic activity. A landslide in Yushu area of Qinghai Province, China, is selected as the main research object and engineering example. This research takes softening effect of dynamic load on the strength of rock, soil, and the law of seismic wave propagation in slope as theoretical basis. The actual damage characteristics of slope in the earthquake are the basis as well. The geomechanics theory is used to simplify the geomechanics model, and large-scale shaking table test is used to carry out the study of instability mechanism. Combined with the FLAC3D elastoplastic theory, the following conclusions are mainly drawn: (1) single slip surface under earthquake, the deformation characteristics of accumulation layer landslide are cracks in the middle of slope → development toward the front edge of slope → deformation of the trailing edge of traction → tension cracks; (2) according to calculation of the point safety factor, the sliding process of the 2# landslide, it exhibits the characteristics of pushing slip, and the sliding mechanism of accumulation landslide is not affected during earthquake; and (3) the slip zone soil has an obvious blocking effect on acceleration amplification effect of the landslide body.
The instability and damage of loess slopes under strong ground motion can be a complicated process, involving sliding, translation, and rotation, which makes the discrete element method as a suitable theory to simulate such a process. Therefore, in this study, the particle flow code (PFC) is developed to simulate the instability and damage process of the loess landslide under strong motion. Based on field investigations and laboratory tests, the detailed identification of mesoscopic parameter was calibrated, and a 2D model was established. The results show that the slope surface tends to amplify the ground motion, resulting in the strong vibration of the soil on the slope surface. The slope shoulder is the position with the largest amplification coefficient of seismic acceleration, which is the key to the instability and failure of the slope. And, under the seismic force, the tensile failure firstly occurs in the slope upper part, and then the accumulation failure occurs in the lower part, finally a shear outlet is formed. Accordingly, high-frequency component of the Fourier spectrum increases with the slope failure. This study highlights the gradual increase in the difference between the first principal stress and the third principal stress, which destroys the inherent cohesive cements between particles, which is the main cause of slope failure under strong motion.
The main objective of this study was to investigate the effect of input earthquake characteristics on the seismic response of a homogenous step-like rock slope. A sequence of shaking table tests was performed in a large-scale physical model with a size of 3.50 m, 0.68 m and 1.20 m in length, width and height, respectively. Results showed that the absolute peak ground acceleration motion amplification factor in horizontal direction (AAF-X) of upper part of the slope was amplified comparison with that at the slope toe while the absolute peak ground acceleration motion amplification factor (AAF-Z) acquired maximum value at the lower position of the slope. With the increasing of the excitation frequencies, the AAF-X around the slope crest increased firstly and then deceased, while the AAF-Z increased continuously. Seismic response of the slope showed strongest amplification when the normalized height of the slope H/λ (ratio of slope height to wavelength) was around 0.2 and AAF-X exhibited a decrease trend when H/λ was larger than 0.2. The AAF showed nonlinear tendency with the increases of the input amplitudes, especially near the shoulder of the slope. This phenomenon can be revealed by the relationship between the calculated resonance frequency or damping ratio of the slope and the amplitude of the input motion. The excitation amplitude has a “double-effect” on the seismic response of a step-like homogeneous rock slope. That is on the one hand, the larger the excitation amplitude, the stronger the acceleration intensity, the greater deterioration of rock slope structure or material and the larger damping ratio of the slope; on the other hand, more energy will be dissipated due to plastic deformation or particle friction of high damping ratio and weaker slope structure. These results could attribute to reveal the dynamic instability mechanism of the homogeneous slope.
The mechanisms and characteristics of earthquake-triggered anti-dip rock landslides remain largely unknown. In this study, the dynamic response characteristics and failure process of anti-dip layered rock slopes are investigated under strong earthquake conditions using shaking table model tests and numerical analysis. The test model uses a slope angle of 60° and steep dip angle of 75° and considers different vibration waveforms, frequencies, amplitudes, and durations. Under the same conditions, the seismic wave PGA amplification factor is higher than that of a sine wave. Under the action of the two waveforms, the PGA amplification factor increases nonlinearly with elevation owing to the interaction of the elevation amplification effect and inhibition of the slope toe. The frequency is greater than or equal to the natural frequency of the test model, but the increase is not notable below 3/5 of the slope height. Horizontally, the PGA amplification factor is larger on the top and surface of the slope. The peak PGA amplification factor shifts from the surface to the top with increasing amplitude. With increasing frequency, the PGA amplification factor reaches a peak value at the natural frequency and then decreases. Frequency has a stronger influence on the dynamic slope response than amplitude, and duration has the weakest influence. The dynamic slope failure model results show that the failure mode of an anti-dip rock slope under a seismic load involves the extension of shear cracks and tension cracks and development of step-type fractures, which trigger slope toppling and sliding failure.
Through the shaking table test, Wenchuan wave (WC) was used as the excitation wave of the shaking table test. The vibration was excited in three directions: horizontal (x), vertical (z), and horizontal and vertical (xz) and the dynamic response characteristics of rock slopes was studied. The results show:(1) The acceleration amplification factor of each measuring point of the slope shows a nonlinear increasing trend with the increase of the slope height.The slope changes the frequency spectrum of the loaded seismic wave.The slope has a filtering effect on the high frequency band of the seismic wave.(2) Under the unidirectional cyclic loading of Wenchuan wave, the slope acceleration amplification factor increases with the increase of the peak value of the seismic wave. Under the bi-directional excitation of Wenchuan wave, the slope acceleration amplification coefficient generally decreases with the increase of the peak value of the seismic wave.The slope acceleration amplification factor presents the characteristics of first increasing and then decreasing with the increase of the relative height of the slope.(3) The dynamic displacement response characteristics of the tunnel slope with double-arch tunnel are mainly affected by the seismic wave in the same direction and the peak value of the dynamic displacement response increases with the increase of the seismic wave peak value.(4) The peak dynamic displacement response of the double-arch tunnel slope shows a non-linear change trend with the increase of slope height. The dynamic displacement peak growth rate is slower below the rock interface and the dynamic displacement peak increases rapidly above the interface and Maximum displacement occurred at the top of the slope.
This study investigates a complex slope failure that occurred in Chongqing Xi railway station. The studied slope belongs to a under-dip shale slope. Onsite surveys and UDEC numerical modelling were conducted to describe the deformation characteristics and potential failure mechanism of this slope. The simulated results suggest that sliding, buckling and toppling can occur in the deformation process, which is verified by the actual deformation characteristic of the slope and monitoring results. Moreover, the effects of bedding dip angle, slope angle, bed thickness on the deformation characteristics of the slope were also investigated with UDEC models. Finally, the possible slope structure for occurrence of slide-buckling-toppling failure and several numerically validated remedial measures were proposed.
A large-scale shaking table model test is conducted to study the dynamic behavior of entrance slope and its interaction with lining structure of mountain tunnel under earthquake loading. Test results show that the acceleration response of tunnel entrance slope exhibits obvious amplification effect and surface effect along both vertical and axial directions. Significant nonlinear behavior is observed when the earthquake loading amplitude is larger than 0.6g; and after that, amplification factor decreases with the increase of input loading amplitude and additionally the distribution of acceleration becomes more even in the slope body. It is also found that the dynamic response along axial direction of entrance slope does not affect much by existence of tunnel structure; thus it could be evaluated by treating the entrance slope as a natural slope for simplification. On the other hand, however, the potential instability of entrance slope has much influence on the safety of tunnel structure. When the loading amplitude is relatively small, internal force induced by vertical acceleration is larger than that caused by horizontal acceleration. As the loading amplitude becomes larger, the horizontal component of earthquake plays a dominant role in affecting the lining structure. The failure surface is located at the upper part of entrance slope, especially on the shoulder. The failure process could be described as five steps: (1) earthquake excited; (2) slope shoulder cracked due to tensile failure; (3) the cracked rock of shoulder toppled and collapsed downwards; (4) the collapsed rock fell along the slope and crushed to debris; (5) rock debris accumulated at the slope toe. The experimental result provides valuable basis and guidance for analysis, calculation and design of mountain tunnel portal.
Slope dynamic response to an earthquake is a product of interaction between seismic waves of complex frequencies and slope body; different frequency components induce different slope responses. Through shaking table tests, effect of wave frequency on two model slopes is analyzed. The two model slopes are composed of the same materials of high strength, but different structures, isotropic and layered. Firstly, dynamic characteristics of model slopes calculated through excitations of white noises show that, resonance frequency of each model decreases and the internal structure becomes loose as the test is going on; and the first resonance frequency of horizontal component acceleration is larger than that of vertical component acceleration. Then, emphasis is put on the slope acceleration responses and their correlations with changing frequencies. Results show that: (1) Obvious topographic amplification occurs in relative elevation h/H>1/2 for horizontal component acceleration; while topographic amplification occurs in relative elevation h/H<3/4 for vertical component acceleration;and the phenomena are independent of the excitation frequency. (2) Under the same excitation intensity, the horizontal component motion produces stronger response as the excitation frequency is increasing, more close to the resonance frequency. The correlation between vertical component response and frequency depends on the structure of model slope. (3) When the excitation intensity increases, the decay of slope structure (i.e. decease of resonance frequency) does not always cause attenuation of response, instead, high frequency excitation still can produce strong response due to the narrowing gap between excitation frequency and resonance frequency. (4) The layered model slope responses more severely than the isotropic model slope. Under strong motion, the structure effect is intensified for horizontal component and weakened for vertical component as excitation frequency increases.
In order to investigate the distribution rules of acceleration, speed and displacement (short for three parameters) responses of a slope subjected to an earthquake, a 3D model for an ideal slope was established based on the Lagrangian finite difference method. Effects of slope form on the distributions of the three parameters were analyzed by introducing the concepts of amplification coefficients of the three parameters and drawing corresponding contour graphs, and were verified by the 3D model for an actual slope. The research results indicate that to a slope with a medium and certain height, its three parameters increase with the increase of slope height, and their amplification coefficients increase also. The distributions of the three parameters are related to the slope form, the amplification coefficients of the three parameters are maximum at concave and convex parts of the slope. And the more intense the degrees of the concave and convex parts are, the more obvious the amplification effect is. Furthermore, the amplification effect of a convex slope is stronger than that of a concave slope as a whole.
A new definition of peek ground acceleration (PGA) magnification factors is proposed to represent the peek value of dynamic response acceleration for the rock mass slope, then the change of the maximum value of PGA magnification factors is regarded as an intuitionistic and typical variable, which is used to reflect the sensibility of seismic dynamic response. A 3D discrete element model is built to simulate the seismic dynamic response under the effect of discontinuity, in which dip angle, initial position, shear stiffness, normal stiffness and spacing distance are the five varying factors. Considering the correlations and random linkage of discontinuity factors, orthogonal experimental design method is applied to obtain the whole experimental scheme. Mathematic statistics analysis methods are used to put the sensibility of the maximum value of PGA magnification factors in order. The result of range analysis and variance analysis implicates that the sensibilities of dip angle, initial position, shear stiffness, normal stiffness and spacing distance of discontinuity are in descending orders.
In order to investigate the vibration correlation of a low-pylon cable-stayed bridge and its cable components under different running speeds, the interaction between the whole structure and its cables was considered by taking a railway low-pylon cable-stayed bridge with a main span of 115 m+95 m as an engineering background, and the vibration responses of beams and towers and the local vibration responses of cables were obtained with the method of numerical integration based on the train-track-bridge coupling vibration theory. The research result indicates that the cable-beam vibration correlation under a train load is essentially an energy transfer process. The vibration energy transfers easily in the condition that the frequency of displacement excitation at cable end is close to the nature frequency of cables. When a train is passing through a bridge at a design speed of 225 to 350 km/h and the excitation frequency is close to the nature frequency of cables, the resonance of cables will occur under external excitation, but the resonant amplitudes are not great, local vibration amplitudes of cables being less than 3 mm.
The weak layer in a slope always controls slope deformation and failure mode. Under an earthquake, the complex interaction mechanism between the weak interlayer and the seismic waves hinders the understanding of the dynamic responses of this type of slope. Based on the existing knowledge, shaking table tests were conducted for four slope models containing a weak interlayer. The effects of the weak interlayer were uncovered by comparing the responses of the models with and without a weak interlayer. Both the horizontal(PHA) and vertical(PHA) acceleration responses were amplified along the altitude for all four slope models, especially in the locations with the elevation higher than the interlayer. In the locations with the elevation lower than the interlayer, the PHA amplification factor remained within 1.5. In comparison with the homogeneous model, the existence of an interlayer resulted the two component responses in the upper part of slope strongly depended on the features of the interlayer and the input intensity. When the input intensity was weak(≤0.3g), the responses for the models with a thin or a thick interlayer were stronger than in the homogenous model. With the increasing of the input intensity, the thick interlayer generated an effect of seismic isolation, which caused the PHA and PVA responses at the slope crest decreasing by 50% and 70% respectively. The horizontal displacements on the slope surface were amplified and reached the maximum value at the crest. The initial deformation occurred at the top of for the homogeneous model slope. However, for the four models with a weak interlayer, the deformation was firstly observed in the position above the interlayer and below the crest. The location and the degree of the slope failure were closely related to the thickness and the dipping angle of the weak interlayer. The model with a horizontal interlayer caused the failure location higher than the models with an anti-dip interlayer and the model with a thin interlayer caused the failure more severe than the one with a thick interlayer.
Dynamic response characteristics and failure process of antidip layered rock slope under strong earthquake are studied by large-scale shaking table model test inputting sine wave in X-direction and XZ-direction. Testing results show that:(1) Acceleration amplification coefficients increase nonlinearly with the increase of slope height. The slope has the nonlinear height effect, i.e. more obvious of amplification more closing to slope top, and nonlinear surface effect, i.e. more intensity of amplification more closing to surface. (2) 3/4 of slope height is the critical height. Horizontal acceleration is amplified more obviously than vertical acceleration while above the height;but when below the height, the vertical acceleration is amplified more obviously. (3) The effect of frequency of seismic wave on the acceleration amplification coefficients is the largest. While the seismic frequency approaches to slope body(s natural frequency, the amplification effect is more obvious and the critical height is lower. (4) The amplitude of acceleration has no influence on distribution of its amplification coefficients in slope;but the larger the amplitude of acceleration is, the more the amplification coefficient is. (5) Failure process of the antidip layered rock slope under earthquake is divided into the following stages:earthquake induction;opening of structural surface at the top of slope;opening of structural surface at slope surface;increases of opening number of surface structural surfaces and depth of opening range, model blocks shearing broken at inner slope;rock structure loose at upper part and slope surface and arc transfixion crack along slope appearing. The zonal deformation phenomenon in the test has testified that distribution of acceleration coefficient in slope body is nonlinear.
Large-scale shaking table experiment was carried out to study the dynamic response of the front slope of tunnel entrance with weak layer has, and general conclusions were obtained through analyzing the acceleration and failure modes of front slope of tunnel entrance and tunnel lining under the horizontal and vertical excitation. The results showed that the front slope had an obvious acceleration magnified effect under the horizontal excitation and the weak layer produced a significant impact on the dynamic response of the front slope under vertical excitation; The peak acceleration of the tunnel lining at the entrance was larger than that far from the slope surface, at the entrance the maximum peak acceleration occured in the vault while that minimum occured in the invert, the forced state of the lining was complicated; With vertical acceleration excitation, the overlying soil model of the weak intercalation loosed, the soil at the toe of slope squeezed and fall-block, however the slope remained stable overall; Under the action of horizontal excitation, the soil at the toe of the front slope crushed first, and then the slope surface location along weak intercalation cracked, the overlying soil layer along weak intercalation slided, at last large-scale dilapidation and fall occured; Under the vertical and horizontal vibration force, the maximum strain amplitude occured in the 45° of the lining, the fortified length of tunnel portal section is 25 m. These conclusions can be reference for design, construction and study on the tunnel seismic study.
The acceleration response can be used to analyze the mechanisms of a landslide and to determine the coefficients of earthquake influence reasonably. The centrifuge shaking table test of 50g modelling the colluvial landslide was carried out. The landslide model was placed in a rigid aluminum alloy container with the length of 600 mm, width of 400 mm and height of 500 mm. The bedrock wave recorded at Qingxi station during the Wenchuan earthquake was exerted from the bottom of the model. The amplification coefficients of the horizontal and vertical peak ground acceleration(PGA) at landslide surface were found to increase with the increasing of the elevation. The increasing rate of the amplification coefficients of PGA at the measured spots near the slope crest was notably larger. The acceleration response at the slope surface was significantly different from that inside the landslide. The horizontal acceleration at bedrock had the amplification effect along the elevation of the landslide, but was much smaller than that at the landslide surface. A phenomenon of wave mode transformation was found at the crest of the landslide. The amplification coefficients of PGA at the crest of landslide increased firstly and subsequently decreased with the increasing of the amplitudes of the input seismic wave.
To study the dynamic response of homogeneous slopes supported by lattice beams under earthquake, a small slopes model made of silica gel on shaking table was designed at the geometric scale of 1:15. Under the same sinusoidal loading, the range of the strains at the same measuring point on the lattice beam is found to be largely unchanged before the failure and the strains varied sinusoidal accordingly. But in the stage of failure, the dynamic strains vary irregularly and reach very large values finally in the destruction phase. Additionally, the stress level of the horizontal lattice beam is the same as that of the vertical lattice beam under the same seismic excitations. For the horizontal lattice beams, the strains at the middle of the beams are larger than those at two ends of the beams. And for the vertical beams, the strains from the top to the bottom exhibit a feature of larger- smaller-larger-smaller variation, indicating that the slope deformation along the vertical beams are restrained by the anchors. When the frequency of the sinusoidal loading is the same, the dynamic strains on the lattice beams increase with the increasing of the seismic acceleration. When the input acceleration is the same, the measured strains are larger at low frequency cases than those at high frequency ones. The reason is that the input low frequency is close to the natural frequency of the model and thus the dynamic responses in low frequency conditions are stronger. The results demonstrate that the silicone slope model is suitable for studying the dynamic response of the slope with supporting structure. The model can be used repeatedly and greatly reduces the cost of test.
At present, the deformation analysis in the large-scale landslide physical model tests is mainly carried out with point based measurements which are generally more accurate and precise than area based techniques, especially when control targets are used. However, point based measurements provide only information of a few selected monitoring points and not on the whole surface of the model. 3D laser scanning technology captures the integrated, comprehensive, consecutive and associated panoramic coordinate data with a high degree of precision and resolution in extreme speed. It also describes factually the frame and configuration of the object. 3D laser scanning technology has been successfully applied to displacement monitoring and deformation measurement in the large-scale landslide physical model tests. In order to assess the effectiveness of the measurement methods applied to measure displacement in the laser scanning and evaluate their performances, a validation simulation experiment has been carried out. The error evaluation model of the point positional accuracy is derived. The point density in laser scanning is analyzed theoretically; and a practical test stabilized with model piles has been carried out to better understand the mechanics of such type of landslides. The displacement and deformation obtained by cloud to cloud comparison method, the barycenter method and scan data collection at two different epochs are reasoned to describe synthetically the deformation evolution process of the model here. Researches show that: the error evaluation model and point density model provide a theoretical basis for the evaluation of measurement achievement and the optimal designs for the measurement scheme. The cloud to cloud comparison method and scanning data collection techniques are area based measurements, while barycenter method and the benchmark method are point based. With point based measurement small deformations can be detected in only a few selected positions due to the largely manual measurement process. The area based methods give a good approximation of the displacement amplitudes and provide the whole deformation of the slope surface. The application of the 3D laser scanning technology to the landslide model test has the advantage of combining both the point based and area based methods. It provides the whole deformation while maintaining the high precision for the selected positions.
After analyzing the propagation of stress wave at different angles of inclination, strength parameters and the group number of structural plane. The results of research are summarized as follows: Due to the change of propagation direction in structural planes with different angles of inclination, the original propagation rule of stress wave changes too, the peak velocity of the monitory point gets relatively flat as the strength parameters of structural plane turn greater. Stress wave repeatedly refracts and reflects in many groups of structural plane, then the appropriate dynamic characteristics of the wave no longer maintains as the number of group increases or decreases. By analyzing and verifying the slope instance, the test result provides a reference for studying dynamic response rules.
Wenchuan Earthquake induced thousands of rock fall and collapses, with some unique kinetic characteristics of geohazard. In order to study the genetic mechanism of the geohazards induced by strong earthquake, the influence of the factors such as the direction of the seismic force, texture of the slope, shape characteristics of slopes, on the slope' failure and discussed the main model and process of the slope' failure under strong earthquake were investigated, by the means of shakding table model test of physical modeling. The results showed that strong inertia force formed in the process of earthquake is the main reason of the slope's distortion and failure. The strong horizontal seismic inertia force brought vertical tensional cracks which strike perpendicular to the direction of the seismic force on the top of the slope firstly. At the same time, it drived the plasmodium on the out side of the crack move along the horizontal direction, brought the tensional and shearing texture face or slip face which is horizontal or incline outside. At last the slope failed along this face. The lithology of slope and the characteristic combination of lithology, the characteristic combination of the control texture faces are the main factor of the model of slope's distortion and failure under the strong earthquake.
The research progress of geomechanical model test are introduced, including new model material, combination test apparatus and new measurement technologies of strain and displacement and so on. New model material can simulate engineering rock mass better and has characters of low cost, easily drying and recycling. The developed combination test apparatus can assemble freely and has high stiffness and good integral stability. Hydraulic pressure loading system can implement automatic servo-controlled and ladder-shaped loading. Strain can be measured by advanced high-speed static strain collection analysis system and fiber measurement technology. Model interior displacement can be measured by the developed fiber Bragg grating mini-type multi-point extensometer. The surface displacement of tunnel can be measured by calipers, photograph measure and CCD laser displacement sensor. These measuring methods mentioned above have characters of automatization, high precision and less disturbance, which can get more accurate test results. Finally, an example is provided to illuminate the application of geomechanical model test in forked tunnel research.