No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Evaluation of Loess Landslide Disaster Based on the Developed Hyperbola Strength of Structural Loess
Abstract
Shear and tensile strengths are two aspects of the mechanical properties of structural soil. Firstly, this study determined the tensile strength of structural loess through experimental testing. Secondly, the hyperbola strength of structural loess was determined by combining the test results of tensile and shear strengths, and the algorithm was further investigated by modifying the corresponding failure stress according to the hyperbola strength. Thirdly, the structural parameter of stress ratio and the structure property were introduced into the hyperbola strength theory of structural loess. Finally, this study analysed the triggering mechanism of structural loess's landslide disaster. The results proved that the rainfall increased the water content of the slope soil. Hence, the structure property of the structural loess decreased, which led to a reduction in its tensile strength. The safety factor of the structural loess slope gradually decreased with the occurrence of instability. The hyperbola strength of structured loess established in this study effectively overcame the defect of exaggerated tensile strength based on the Mohr-coulomb strength theory and provided a practical strength theory that evaluates the engineering disasters of structural loess slope.
... Xie et al. studied the effects of matrix suction and net confining pressure on the deformation and strength characteristics of compacted loess by carrying out the triaxial consolidation shear test of unsaturated loess, and the results showed that under certain matrix suction conditions, the shear strength of compacted loess increased with the increase of net confining pressure, and under constant net confining pressure, the shear strength increased with the increase of matrix suction [25]. When the strength of structural loess is higher, it not only has higher shear strength but also has relatively higher tensile strength, and tensile strength considerably affects the mechanical properties of structural loess [26]. Therefore, the influence of tensile strength of structural loess should be considered when the stress and displacement of the surrounding rock of structural loess tunnel need to be studied. ...
... The ultimate equilibrium state of the joint strength on the σ-τ plane is ure 3, where σ1 is major principal stress and σ3 is minor principal stress. To fit a hyperbolic curve of the joint strength line of structural loess on the σ-τ plane, Li et al. assumed that the horizontal axis intercept of the curve represents the tensile strength σ t , and that the M-C strength envelope was regarded as the asymptote [26]. Then, the joint strength formula corresponding to the dotted line, which can describe the tensile and shear strengths of structural loess comprehensively and reasonably, was derived on the basis of the tensile and conventional triaxial shear strength tests. ...
... At the interface between the elastic and plastic zones, r equals R and η equals η R . Accordingly, Formula (16) becomes Formula (26). ...
The development of an effective evaluation method suitable for loess-tunnel excavation is necessary to avoid the collapse accidents caused by tunnel excavation and any secondary disasters. Although the Fenner formulas and the modified Fenner formulas are widely used in tunnel engineering, a defect still exists in these formulas because the Mohr–Coulomb (M–C) criterion exaggerates the tensile strength of the surrounding rock of the loess tunnel. A newly modified Fenner formula was derived based on joint strength to overcome this deficiency. First, the expressions of stress and the radius of the plastic zone of the surrounding rock of the loess tunnel and the expressions of radial displacement were derived based on the stress-equilibrium equation of the axisymmetric plane and the joint strength. Then, the difference in the modified Fenner formulas based on the two kinds of strength criteria for the loess tunnel were compared. The results showed that the radius of the plastic zone and the radial displacement of the loess tunnel determined by the modified Fenner formula based on joint strength were larger than those determined by the modified Fenner formula based on M–C strength. However, the plastic stress of the plastic zone determined by the modified Fenner formula based on joint strength was smaller. The comparative analysis reveals that the modified Fenner formula based on joint strength can evaluate the stress and plastic-displacement field of the surrounding rock of a loess tunnel more reasonably.
... Due to its unique sedimentary conditions and stress histories, it usually exhibits notable engineering characteristics, including structural and water sensitivity (Pan et al. 2021;Chen et al. 2019;Wang et al. 2021a, b;Leng et al. 2021). The soil structure will be destroyed under loading and humidification, leading to obvious collapsible deformation, which seriously affects the progress and safety of engineering construction projects (Li et al. 2013;Deng et al. 2018;Duan et al. 2019). Hence, it is of great practical significance to develop a constitutive model of collapsible loess with clear physical meaning and simple form for the engineering applications. ...
The structural evolution of loess under load and humidification plays an important role in the safety evaluation of engineering in loose area. A simplified constitutive model is developed by incorporating the structural composition of collapsible loess in this paper. The user defined material subroutine (UMAT) of this model is programmed using an improved Euler integration algorithm with error control. A stress correction technique is incorporated in the UMAT subroutine to improve the computational accuracy and efficiency. Comparisons between UMAT subroutine simulation results, existing experimental results and result from the MATLAB program shows the validity and stability of this UMAT subroutine. Examples of three-dimensional square foundation and pit excavation using the UMAT subroutine is analysed, the simulation results demonstrates its reliability in capturing the general features of the wetting collapse for collapsible loose. These results can provide reference for the secondary development of relevant critical state models and offer a new approach for the engineering application of constitutive models for collapsible loess.
... Xie et al. [4] proposed a structural parameter that comprehensively reflects soil structure. Li et al. [5,6] established a nonlinear damage constitutive equation for unsaturated loess considering structural effects. Luo et al. [7] and Shao et al. [8] proposed a structural constitutive relation and suggested a humidification constitutive model considering the structure of unsaturated loess. ...
Loess has a unique structure and water sensitivity, and the immersion of loess leads to many tunnel lining problems in shallowly buried tunnels. Based on a tunnel in Gansu Province in China, two failure glide planes of a shallowly buried loess tunnel and their immersion modes are summarized. Finite element calculation of the structural Duncan-Chang constitutive model is realized via the secondary development of finite element software, by which the loads on the secondary lining are calculated and verified in comparison with measured results. The load characteristics of the secondary lining are studied. The load evolution is closely related to the immersion position and scope of the load. After the loess near the failure glide plane of the arch foot is flooded, the load on the arch foot sharply increases. As the immersion expands, the maximum load moves from the arch end up to the hance. After the loess near the failure glide plane of the hance is flooded, the load on the hance decreases slightly. The stability of the overlying loess decreases gradually, which causes the loads on the vault and arch shoulder to rapidly increase. Additionally, the load distribution characteristics on the secondary lining are summarized.
ResearchGate has not been able to resolve any references for this publication.