Wendong Yang

China University of Petroleum · College of Pipeline and Civil Engineering

This work introduced a novel numerical approach for modelling hydraulic fracturing processes. The Edinburgh bonded particle model was employed to establish the discrete element model of the rock samples, and it was further coupled with computational fluid dynamics to simulate the hydraulic fracturing. The fracture propagation law was taken into acc...

Complex fractures and pore structures in the rock strongly influence the mechanical properties, and the process from compression to failure is complicated. Under the action of rock stress, pore structure deformation and fractures close or propagate, easily leading to deterioration in the rock mechanical properties until rock failure. Thus, the effe...

Fractured karst geothermal reservoir is a kind of typical geothermal reservoirs with the advantages of abundant storage water and easy reinjection of tail water during the period of geothermal utilization. Such geothermal system is also one of the geothermal reservoirs with the greatest potential for the development and utilization of geothermal en...

The unloading effects induced by rock excavation on high slopes are significant, and a prestressed anchor cable is an effective reinforcement method for high-slope safety. In this work, we consider the interaction between rock creep in high slopes and the changing anchoring force of prestressed cables. We then derive theoretical solutions for the u...

Energy-absorbing anchor bolts are widely used in geotechnical engineering, but there is no effective numerical simulation approach for evaluating them at the engineering application level. According to typical laboratory test results, the energy absorption criterion (F ≥ Fy) and breakage criterion (δ ≥ δf) are defined. The constant resistance energ...

High-temperature (> 150 oC) geothermal resources have great potential for sustainable power generation. These geothermal resources can be exploited efficiently through highly permeable geological structures, i.e. tectonic fractures and dissolution caves, which thus are categorized as fractured and karstified geothermal reservoirs. However, the stud...

The unloading effects induced by rock excavation on high slopes are significant, and prestressed anchor cable is an effective reinforcement method for high slope safety. In this work, we consider the interaction between rock creep in high slopes and the changing anchoring force of prestressed cables. We then derive theoretical solutions for the unl...

Calcium silicate hydrates (C-S-H) is the main hydration product of cement, and C-S-H gel is a porous structure. The physicochemical reactions of harmful ions in the external solution, such as chloride ions and sulfate ions, will cause the hydrolysis of C-S-H gel and therefore resulting in the decrease of the strength of the concrete. In this work,...

To promote hydraulic refracturing, plugging hydraulic fractures through forming artificial barriers with temporary plugging agent (TP) as an effective method has been widely used. Innumerable researches have been carried out on the process, mechanism, and influence factors of hydraulic fractures plugging. Despite great achievements, the fluid infil...

Laboratory experiments are an effective way to study the initiation and propagation of hydraulic fractures for the complex stress level and structure of underground reservoirs. However, it is difficult to observe hydraulic fractures directly in rock or mortar specimens. In this study, a kind of transparent rock-like material whose tension–compressi...

The generation of a highly permeable fracture network in Enhanced Geothermal Systems (EGSs) is a prerequisite to develop such geothermal reservoirs efficiently. However, it lacks a quantitative geometrical metric to evaluate what kind of fracture network is preferable for geothermal production. To address this problem, we use our previously develop...

Mechanical properties of the interface between a pile and soil greatly affect the bearing capacity of a pile. The creep of soil causes a long-term strength of the pile–soil interface to be smaller than its instantaneous shear strength. It is helpful to understand the settlement deformation and strength characteristics of friction piles from the mic...

Temporary plugging agent (TP) fracturing has been widely used in many cases as an efficient technology to improve well production performance. In particular, the initiation and propagation of hydraulic fractures are vital to the evaluation of fracturing effect. Hence, the research of its influencing factors and laws is crucial for successful design...

Plugging upper and lower tips of hydraulic fracture by forming artificial barrier with diverting agent is as an effective method to prevent hydraulic fracture height from extending excessively. This work, obtained the transient analytical solutions of both fluid pressure decrement generated by artificial barrier (Δp) and equivalent permeability bet...

Shear dilation of fractures has been recognized as a main mechanism of permeability enhancement by hydraulic stimulation in Enhanced Geothermal Systems (EGSs); however, the interactive role of fracture shear dilation and thermo-hydro-mechanical (THM) coupling processes in long-term heat extraction performance of EGSs remains unclear. In this study,...

Creep properties of interlayered rock mass often encountered in rock engineering, significantly affect the safety and long-term stability of practical engineering. In this study, the theoretical equations of creep strain for interlayered rock specimens when the uniaxial compression loading was applied perpendicular to or parallel with bedding plane...

Multiple hydraulic fracturing treatment from horizontal wells has been widely used to enhance the productivity of unconventional hydrocarbons. Interaction among the fractures can cause the reorientation of fractures and lower the stimulation efficiency. We perform discrete element method (DEM) simulations to assess the influence of completion schem...

True triaxial hydraulic fracturing experiments were carried out on artificial analogue rock samples (AARS) of tight sandstone to analyze initiation characteristics under different fracturing fluid (FF) infiltrations. Moreover, the initiation was monitored by acoustic emission (AE) system. The results show that: FF fracturing has the lowest initiati...

Rock with multiple discontinuous joints widely exists in rock engineering, and its mechanical properties are complex, which greatly increases the difficulty of engineering design and construction. Time-dependent deformation characteristics and long-term strength evaluation of jointed rock masses remain poorly understood. In this work, the creep exp...

Pre-stressed bolt anchorage is the key technology for jointed rock masses in rock tunnelling, slope treatment and mining engineering. To investigate the mechanical properties and reinforcement effect of jointed rock masses with pre-stressed bolts, in this study, uniaxial compression tests were conducted on specimens with different anchoring types a...

Faults in the rock mass of dam foundation are crucial in controlling dam deformation and stability. In particular, long‐term stability of dam foundation is an important factor for the safety of dam operations. The rock in the foundation of Dagangshan hydropower station is mostly granite, and there are many diabase dikes distributed in granite. Geol...

As the main way of oil and gas long-distance transportation, buried pipelines will inevitably pass through the active fault zones. Fault displacement induced by earthquake, especially the oblique-reverse fault displacement, will cause large compressive, tensile and bending strain in the pipeline, resulting in buckling, rupture or warping, which ser...

The stability of rock engineering applications is significantly influenced by the mechanical behavior of jointed rock masses. However, the deformability, strength and failure characteristics of non-persistent jointed rock specimens have not been examined comprehensively. In this paper, laboratory tests and discrete element method simulations are us...

Fossil fuel resources (eg, coal, oil, and natural gas) exist in underground reservoirs, where discontinuities are widespread and influence the stability of rock structures. The mechanical behavior of jointed rock masses significantly affects the long‐term stability of rock engineering. A major challenge in this area is to link the time‐dependent de...

The mechanical behavior of jointed rock masses significantly affects the stability of rock engineering applications. In this paper, the peak strength, Young's modulus and failure patterns of brittle rock-like specimens with multi-non-persistent joints under uniaxial compression are investigated. The joint geometry is defined by four factors: joint...

Many rock engineering accidents have proven that the coalescence of discontinuities in surrounding rock can have a major impact on the security and stable operation of energy infrastructure. To give an insight into the understanding of the crack propagation and coalescence in fissured rock masses, a series of uniaxial compression experiments were c...

The creep characteristics of rocks are very important for assessing the long-term stability of rock engineering structures. Two loading methods are commonly used in creep tests: single-step loading and multi-step loading. The multi-step loading method avoids the discrete influence of rock specimens on creep deformation and is relatively time-effici...

In order to study the deformation mechanism of the weak layer in diabase dikes under long-term loading at a hydropower dam foundation, in situ plate loading tests were performed. A damage creep model which improved the five-parameter generalized Kelvin model was established to describe the creep behavior of the weak layer. In this model, the deteri...

The seismic response analysis of project soil site is important to obtain the ground motion parameters for seismic design of upper structures. First, a simplified solving method is introduced, in which, the horizontal seismic loadings are expanded into Fourier series in the circumferential direction, using the orthogonality between the normal and t...

Thermal production is an important heavy oil recovery method , which bothers with the complex problems of Thermo-Hydro-Mechanical coupling effects and reservoir failure processes due to thermal recovery. Based on the coupling theory of T-H-M, the fully coupling equations of heat transfer, fluid seepage, geomechanics, and reservoir damage are constr...

Volume change influences the strength and deformation characteristics of rock. A series of conventional triaxial compression, fatigue and creep tests was performed to investigate the influences of shear contraction and dilation on the integrity, fatigue and creep behaviors of rocks. It is found that (1) the dilation of rock decreases with the incre...

Based on triaxial rheological experiment, a nonlinear visco-elastoplastic rheological model is proposed which has creep threshold value, long-term strength, nonlinear viscoplastic body and other components. There are many problems in programming of this complex rheological model, for example, one-dimensional creep threshold value and long-term stre...

Triaxial creep tests were performed on diabase specimens from the dam foundation of the Dagangshan hydropower station, and the typical characteristics of creep curves were analyzed. Based on the test results under different stress levels, a new nonlinear visco-elasto-plastic creep model with creep threshold and long-term strength was proposed by co...

Engineering rock mass is a highly complex grey system, it is impossible to get all the parameters of rock mass by theoretical methods or field measurement approach. Underground engineering feedback analysis method is a reliable way to improve the design, optimization and construction. Based on the field data of underground cavern of a large-scale h...

The unloading triaxial rheological tests by keeping σ 1 and unloading lateral stress or by keeping σ 1-σ 3 and unloading laterals stress by steps were performed in laboratory with diabase samples taken from Dagangshan hydropower station dam foundation. The rheological deformation characters by the two different stress path were analyzed. The yield...

On-site experiments are crucial to study rock mechanics due to the complexity and diversity of rock mass. In the past, test conditions restrain the test load setting of rock creep to transient creep, thus it cannot reflect steady-state creep and accelerated creep. The mechanical characteristics of weak rock mass are vital factors which affect the l...

The rheological property of rocks is an important factor affecting the stability of dam foundation. The rheological long-term strength is an important mechanical index for evaluating the long stability of dam foundation. The rheological long-term strength of diabase is analyzed by using the stress-strain isochronous curve method, unsteady creep dis...

The long-term shear rheology strength of rock mass is an important base to the analysis of long-term operation stability of the rock engineering. Based on field shear rheology test data of dam zone diabase of Dagangshan hydropower station, the long-term shear rheology strength was obtained by stress-strain isochronal curves method, steady-state cre...

Field shear creep test is the most important means to understand the shear creep properties of rock mass. Field shear creep tests are carried out for the dam zone "hard brittle shatter" diabase dikes in Dagangshan hydropower station. The deformation law of shear creep and the characteristics of shear creep rates have been analyzed. The test results...

In order to study the long-term mechanical properties of the diabase in Dagangshan hydropower station dam site, triaxial rheological tests under different stress paths were carried out on RLW-1000 rheology testing machine, and the stress-strain-time curves under different conditions were obtained. The results showed that the diabase was typical har...

Single specimen is used for rheological test method under multistep loading, which avoids the discrete affection of specimen for rheological deformation. But the deformation of the later loading contains the creep deformation induced by the former loading of all levels by this method, which always makes people confused. The memory effect of loading...

Time-dependent deformation behavior of rock has a significant impact on the stability of rock slopes or underground constructions, and more and more attention is paid to the rheology of rock. However, most rock rheological constitutive models supplied by FEM software have specific usage, and the requirement of engineering numerical analysis can not...

In view of the influence of completely and intensively weathered stratum in the shallow surface of slope and fault fracture belt on the initial geostress field in dam zone of Dagangshan hydropower station, the 3D initial geostress regression analysis model is established based on the measured geostress data and geologic structure as well as topogra...

Considering effects of weakness of rock parameters, a creep damage constitutive model with variable parameters is proposed. In the model, the creep parameters of the rock are weakened with time gradually, so the deterioration process of the material can be reflected by unsteady creep parameters directly. The central difference equation in three-dim...

In order to get the compression creep parameters of deep rock, the center hole deformation test of rigid bearing plate is carried out in site. The generalized Kelvin model's instantaneous elastic deformation of deep rock under circular rigid bearing plate which bears the uniformly distributed load is deduced. Based on the viscoelastic theory, throu...

The mechanical parameters of a rheological constitutive model for rock are usually assumed constant, and all the mechanical parameters of rock masses are considered unchangeable with time. Actually, under the effect of geotectonic movement, groundwater seepage, natural weathering and many other factors, the mechanical parameters of rock masses vary...

The center hole deformation test of rigid bearing plate is an important method for understanding deformation properties of deep weak rock mass. According to the center hole deformation test of rigid bearing plate in dam zone of Dagangshan hydropower station, this paper detailedly recommends test method of this experiment, and the settlement deforma...

Due to lots of hypothesis, the theoretical analytical solution of the creep parameters inversion can not reflect the in-situ conditions actually. In order to simulate the process of the compressive creep tests of the in-situ bearing plate, the affection of the stratum distribution and the influence of the geological status in site actually, FLAC3D...

Compressive creep test is an important means for understanding creeping mechanical properties of rock mass. The analysis on in-situ compressive creep test information indicates that the soft rock mass in dam zone of the Dagangshan Hydropower station possesses the characteristics of instantaneous elastic deformation, deceleration creep and elasticit...

It is a systems engineering to successfully simulate a part of a bifurcated tunnel using 3D geomechanical model tests. It involves how to determine the areas and scale for which the model tests simulate, how to choose the similar material which simulates rock mass correctly in geomechanics model tests, how to design and manufacture the steel struct...