Anisotropic strength,deformation and failure of gneiss granite under high stress and temperature coupled true triaxial compression

The anisotropic mechanical behavior of rocks under high-stress and high-temperature coupled conditions is crucial for analyzing the stability of surrounding rocks in deep underground engineering.This paper is devoted to studying the anisotropic strength,deformation and failure behavior of gneiss granite from the deep boreholes of a railway tunnel that suffers from high tectonic stress and ground temperature in the eastern tectonic knot in the Tibet Plateau.High-temperature true triaxial compression tests are performed on the samples using a self-developed testing device with five different loading directions and three temperature values that are representative of the geological conditions of the deep underground tunnels in the region.Effect of temperature and loading direction on the strength,elastic modulus,Poisson’s ratio,and failure mode are analyzed.The method for quantitative identification of anisotropic failure is also proposed.The anisotropic mechanical behaviors of the gneiss granite are very sensitive to the changes in loading direction and temperature under true triaxial compression,and the high temperature seems to weaken the inherent anisotropy and stress-induced deformation anisotropy.The strength and deformation show obvious thermal degradation at 200℃due to the weakening of friction between failure surfaces and the transition of the failure pattern in rock grains.In the range of 25℃ 200℃,the failure is mainly governed by the loading direction due to the inherent anisotropy.This study is helpful to the in-depth understanding of the thermal-mechanical behavior of anisotropic rocks in deep underground projects.

A physics-informed neural network for simulation of finite deformation in hyperelastic-magnetic coupling problems

Recently,numerous studies have demonstrated that the physics-informed neural network(PINN)can effectively and accurately resolve hyperelastic finite deformation problems.In this paper,a PINN framework for tackling hyperelastic-magnetic coupling problems is proposed.Since the solution space consists of two-phase domains,two separate networks are constructed to independently predict the solution for each phase region.In addition,a conscious point allocation strategy is incorporated to enhance the prediction precision of the PINN in regions characterized by sharp gradients.With the developed framework,the magnetic fields and deformation fields of magnetorheological elastomers(MREs)are solved under the control of hyperelastic-magnetic coupling equations.Illustrative examples are provided and contrasted with the reference results to validate the predictive accuracy of the proposed framework.Moreover,the advantages of the proposed framework in solving hyperelastic-magnetic coupling problems are validated,particularly in handling small data sets,as well as its ability in swiftly and precisely forecasting magnetostrictive motion.

Theoretical and Numerical Studies on the Coupling Deformation of Global Lateral Buckling and Walking of Submarine Pipeline

Buckling initiation devices/techniques,including sleepers,distributed buoyancy,snake lay,and residual curvature method(RCM),have recently been widely applied in engineering.These initiated buckles may induce a long pipeline to transform into multiple short pipeline segments,which promote the occurrence of pipeline walking.Thus,a pipeline,which is designed to buckle laterally,may laterally and axially displace over time when subjected to repeated heating and cooling cycles.This study aims to reveal the coupling mechanism of pipeline walking and global lateral buckling.First,an analytic solution is proposed to estimate the walking of pipeline segments between two adjacent buckles.Then,the sensitivity of this method to heating and cooling cycles is analyzed.Results show the applicability of the proposed walking analytical solution of buckling pipelines.Subsequently,an influence analysis of walking on global buckling,including the capacity of buckling initiation,buckling amplitude,buckling mode,and failure assessment of the buckling pipeline,is performed.The results reveal that the effect of walking on the buckling axial force is negligible.However,pipeline walking will aggravate the asymmetry of the pipeline buckling and the failure parameters of the pipeline during the post-buckling.

A COUPLED MODEL FOR MUILTIPHASE FLUID FLOW AND SEDIMENTATION DEFORMATION IN OIL RESERVOIR AND ITS NUMERICAL SIMULATION

A mathematical model for coupled multiphase fluid flow and sedi- mentation deformation is developed based on fluid-solid interaction mechanism.A finite difference-finite element numerical approach is presented.The results of an example show that the fluid-solid coupled effect has great influence on multiphase fluid flow and reservoir recovery performances,and the coupled model has practical significance for oilfield development.

Mathematical modeling for coupled solid elastic-deformation and gas leak flow in multi-coal-seams

Based on the new viewpoint of solid and gas interaction mechanics, gas leakage in a double deformable coal seam can be understood. That is, under the action of geophysical fields, the methane flow in a double deformable coal seam can be essentially considered to be compressible with time dependent and mixed permeation and diffusion through a pore cleat deformable heterogeneous and anisotropy medium. Based on this new viewpoint, a coupled mathematical model for coal seam deformation and gas leakage in a double coal seam was formulated and numerical simulations for gas emission from the coal seam are presented. It is found that coupled models might be closer to reality.

Electro-chemo-mechanical analysis of the effect of bending deformation on the interface of flexible solid-state battery

Flexible solid-state battery has several unique characteristics including high flexibility,easy portability,and high safety,which may have broad application prospects in new technology products such as rollup displays,power implantable medical devices,and wearable equipments.The interfacial mechanical and electrochemical problems caused by bending deformation,resulting in the battery damage and failure,are particularly interesting.Herein,a fully coupled electro-chemo-mechanical model is developed based on the actual solid-state battery structure.Concentration-dependent material parameters,stress-dependent diffusion,and potential shift are considered.According to four bending forms(k=8/mm,0/mm,-8/mm,and free),the results show that the negative curvature bending is beneficial to reducing the plastic strain during charging/discharging,while the positive curvature is detrimental.However,with respect to the electrochemical performance,the negative curvature bending creates a negative potential shift,which causes the battery to reach the cut-off voltage earlier and results in capacity loss.These results enlighten us that suitable electrode materials and charging strategy can be tailored to reduce plastic deformation and improve battery capacity for different forms of battery bending.

Numerical simulation of rockburst disaster and control strategy of constant resistance and large deformation anchor cable in Gaoloushan tunnel

The Gaoloushan Tunnel in Longnan City,Gansu Province,China,frequently experiences rockburst disasters due to high in-situ stress.Managing rockburst in deep-buried tunnels remains a challenging issue.This paper employs RFPA(Rock Failure Process Analysis)software to establish a calculation model of constant resistance and large deformation(CRLD)anchorages and analyzes the effects of different support methods and pre-stress levels on rockburst.We simulate the process of tunnel rockburst disasters and find that ordinary anchor support incurs rockburst on the right arch waist and arch top,forming a V-shaped explosion pit.CRLD anchor support has several advantages in rockburst control,such as more uniform stress distribution in the surrounding rock,a uniform distribution of plastic zones,less noticeable damage to the tunnel,and effective control of the arch top displacement.The effectiveness of the CRLD anchor support under varying pre-stress conditions shows that a higher prestress results in a smaller plastic zone of the surrounding rock and arch top displacement and a lower number of acoustic emission signals,which better explains the excavation compensation effect.Moreover,adding long anchorages in the deep surrounding rock area can better control rockburst and reduce surrounding rock deformation.Based on these findings,we propose a comprehensive control system that combines long and short anchorages and provides the optimal scheme based on calculations.Therefore,by using high-prestress CRLD anchor support and the combination of long and short anchorages at critical positions,we can enhance the integrity of the surrounding rock,effectively absorb the energy released by the surrounding rock deformation,and reduce the incidence of rockburst disasters.

A generalized multi-field coupling approach and its application to stability and deformation control of a high slope

Human activities, such as blasting excavation, bolting, grouting and impounding of reservoirs, will lead to disturbances to rock masses and variations in their structural features and material properties. These engineering disturbances are important factors that would alter the natural evolutionary processes or change the multi-field interactions in the rock masses from their initial equilibrium states. The concept of generalized multi-field couplings was proposed by placing particular emphasis on the role of engineering disturbances in traditional multi-field couplings in rock masses. A mathematical model was then developed, in which the effects of engineering disturbances on the coupling-processes were described with changes in boundary conditions and evolutions in thermo-hydro-mechanical （THM） properties of the rocks. A parameter, d, which is similar to damage variables but has a broader physical meaning, was conceptually introduced to represent the degree of engineering disturbances and the couplings among the material properties. The effects of blasting excavation, bolting and grouting in rock engineering were illustrated with various field observations or theoretical results, on which the degree of disturbances and the variations in elastic moduli and permeabilities were particularly focused. The influences of excavation and groundwater drainage on the seepage flow and stability of the slopes were demonstrated with numerical simulations. The proposed approach was further employed to investigate the coupled hydro-mechanical responses of a high rock slope to excavation, bolting and impounding of the reservoir in the dam left abutment of Jinping I hydropower station. The impacts of engineering disturbances on the deformation and stability of the slope during construction and operation were demonstrated.

Coupling mechanism between mining-induced deformation and permeability of coal

The coupling mechanism between mining-induced mechanical behavior and gas permeability of coal is effectively obtained in laboratory.This study means significant understanding of the prevention of coal-gas outburst.The testing samples of coal were drilled from the 14120 mining face at the depth of690 m.Based on the redistribution of stress during the excavation,the coupling test between mechanical state and seepage has been designed using the triaxial servo-controlled seepage equipment for thermofluid-solid coupling of coal containing methane.It is the result that there are two main factors influencing the mining-induced mechanical behavior of coal,such as the change ofσ_1-σ_3 andΔσ_1-Δσ_3.The failure mode mainly depends on the value ofσ_1-σ_3,and the peak strength value mainly depends on the value ofΔσ_1-Δσ_3.The difference of mechanical response between geostress and mining-induced stress has been obtained,which can be a theoretical support for safe mining such as reasonable gas drainage,prevention of coal-gas outburst and gas over-limit.

Numerical analysis of deformation and failure characteristics of deep roadway surrounding rock under static-dynamic coupling stress

In actual production,deep coal mine roadways are often under typical static-dynamic coupling stress(SDCS)conditions with high ground stress and strong dynamic disturbances.With the increasing number of disasters and accidents induced by SDCS conditions,the safe and efficient production of coal mines is seriously threatened.Therefore,it is of great practical significance to study the deformation and failure characteristics of the roadway surrounding rock under SDCS.In this paper,the effects of different in-situ stress fields and dynamic load conditions on the surrounding rock are studied by numerical simulations,and the deformation and failure characteristics are obtained.According to the simulation results,the horizontal stress,vertical stress and dynamic disturbance have a positive correlation with the plastic failure of the surrounding rock.Among these factors,the influence of the dynamic disturbance is the most substantial.Under the same stress conditions,the extents of deformation and plastic failure of the roof and ribs are always greater than those of the floor.The effect of horizontal stresses on the roadway deformation is more notable than that of vertical stresses.The results indicate that for the roadway under high-stress conditions,the in-situ stress test must be strengthened first.After determining the magnitude of the in-situ stress,the location of the roadway should be reasonably arranged in the design to optimize the mining sequence.For roadways that are strongly disturbed by dynamic loads,rock supports(rebar/cable bolts,steel set etc.)that are capable of maintaining their effectiveness without failure after certain dynamic loads are required.The results of this study contribute to understanding the characteristics of the roadway deformation and failure under SDCS,and can be used to provide a basis for the support design and optimization under similar geological and geotechnical circumstances.

Development and application of multi-field coupled high-pressure triaxial apparatus for soil

The increasing severity of ground subsidence,ground fissure and other disasters caused by the excessive exploitation of deep underground resources has highlighted the pressing need for effective management.A significant contributing factor to the challenges faced is the inadequacy of existing soil mechanics experimental instruments in providing effective indicators,creating a bottleneck in comprehensively understanding the mechanisms of land subsidence.It is urgent to develop a multi-field and multi-functional soil mechanics experimental system to address this issue.Based soil mechanics theories,the existing manufacturing capabilities of triaxial apparatus and the practical demands of the test system,a set of multi-field coupled high-pressure triaxial system is developed tailored for testing deep soils(at depths of approximately 3000 m)and soft rock.This system incorporates specialized design elements such as high-pressure chamber and horizontal deformation testing devices.In addition to the conventional triaxial tester functions,its distinctive feature encompass a horizontal deformation tracking measuring device,a water release testing device and temperature control device for the sample.This ensemble facilitates testing of horizontal and vertical deformation water release and other parameters of samples under a specified stress conditions,at constant or varying temperature ranging from-40℃–90℃.The accuracy of the tested parameters meets the requirements of relevant current specifications.The test system not only provides scientifically robust data for revealing the deformation and failure mechanism of soil subjected to extreme temperature,but also offers critical data support for major engineering projects,deep exploration and mitigation efforts related to soil deformation-induced disaster.

Size-dependent thermomechanical vibration characteristics of rotating pre-twisted functionally graded shear deformable microbeams

A three-dimensional(3D)thermomechanical vibration model is developed for rotating pre-twisted functionally graded(FG)microbeams according to the refined shear deformation theory(RSDT)and the modified couple stress theory(MCST).The material properties are assumed to follow a power-law distribution along the chordwise direction.The model introduces one axial stretching variable and four transverse deflection variables including two pure bending components and two pure shear ones.The complex modal analysis and assumed mode methods are used to solve the governing equations of motion under different boundary conditions(BCs).Several examples are presented to verify the effectiveness of the developed model.By coupling the slenderness ratio,gradient index,rotation speed,and size effect with the pre-twisted angle,the effects of these factors on the thermomechanical vibration of the microbeam with different BCs are investigated.It is found that with the increase in the pre-twisted angle,the critical slenderness ratio and gradient index corresponding to the thermal instability of the microbeam increase,while the critical material length scale parameter(MLSP)and rotation speed decrease.The sensitivity of the fundamental frequency to temperature increases with the increasing slenderness ratio and gradient index,and decreases with the other increasing parameters.Moreover,the size effect can suppress the dynamic stiffening effect and enhance the Coriolis effect.Finally,the mode transition is quantitatively demonstrated by a modal assurance criterion(MAC).

Integrable Rosochatius Deformations for an Integrable Couplings of CKdV Equation Hierarchy

We propose a method to construct the integrable Rosochatius deformations for an integrable couplingsequations hierarchy.As applications, the integrable Rosochatius deformations of the coupled CKdV hierarchy withself-consistent sources and its Lax representation are presented.

Experimental Study on Scouring and Silting Deformation of Artificial Beach Under Storm Surge−Wave Coupling

With the increasing construction of artificial beach in coastal areas, it is of practical significance to study the beach surface deformation of artificial beach profile. Previous studies only focus on a single wave dynamic factor, and it is difficult to predict the beach deformation of artificial beach profile under the storm surge-wave co-action. To solve this problem, the cross-section physical model test method was used to study the beach surface deformation of a typical artificial beach profile in Shuangdao Bay, Weihai, Shandong Province, after continuous wave actions till they stabilize. The characteristics of beach surface deformation under the conditions of constant water levels, laddershaped water level combined with corresponding wave elements and storm surge-wave co-action are compared and analyzed. A beach profile model which satisfies the theory of Bruun model is proposed. The test results show that the maximum scour depth of beach under storm surge-wave co-action is smaller and the scour range is obviously larger than that under the condition of constant water levels or ladder-shaped water level. The evaluation of the maximum scour depth by traditional model test tends to be conservative while the evaluation of the scour range is insufficient.The research results can provide scientific reference for designing artificial beaches.

STUDY ON STRIP AND ROLL DEFORMATION COUPLING OF COLD STRIP ROLLING ON 4-H MILL

The cold strip rolling process on a 4 h mill is studied by coupling the 3 dimensional plasticity deformation of the strip with the elastic deformation of the rolls. On the conditions of that the width to thickness ratio of the strip is 660 and the exit strip shapes are respectively edge wave, centre wave and good, the computed results of the transverse distributions of the roll gap, the rolling pressure, the inter roll pressure, and the front and back tension agree with the experimental results well. The studing methods and the studied results are of great importance to forming shape theory and guiding the development of shape control technology.

Overloading of Landing Based on the Deformation of the Lunar Lander

Along with the progress of sciences and technologies, a lot of explorations are taken in many countries or organizations in succession. Lunar, the natural satellite of the earth, become a focus of the space discovery again recently because of its abundant resource and high value in use. Lunar exploration is also one of the most important projects in China. A primary objective of the probe in lunar is to soft-land a manned spacecraft on the lunar surface. The soft-landing system is the key composition of the lunar lander. In the overall design of lunar lander, the analysis of touchdown dynamics during landing stage is an important work. The rigid-flexible coupling dynamics of a system with flexible cantilevers attached to the main lander is analyzed. The equations are derived from the subsystem method. Results show that the deformations of cantilevers have considerable effect on the overloading of the lunar lander system.

Validation and application of three-dimensional discontinuous deformation analysis with tetrahedron finite element meshed block

In the last decade, three dimensional discontin- uous deformation analyses （3D DDA） has attracted more and more attention of researchers and geotechnical engineers worldwide. The original DDA formulation utilizes a linear displacement function to describe the block movement and deformation, which would cause block expansion under rigid body rotation and thus limit its capability to model block de- formation. In this paper, 3D DDA is coupled with tetrahe- dron finite elements to tackle these two problems. Tetrahe- dron is the simplest in the 3D domain and makes it easy to implement automatic discretization, even for complex topol- ogy shape. Furthermore, element faces will remain planar and element edges will remain straight after deformation for tetrahedron finite elements and polyhedral contact detection schemes can be used directly. The matrices of equilibrium equations for this coupled method are given in detail and an effective contact searching algorithm is suggested. Valida- tion is conducted by comparing the results of the proposed coupled method with that of physical model tests using one of the most common failure modes, i.e., wedge failure. Most of the failure modes predicted by the coupled method agree with the physical model results except for 4 cases out of the total 65 cases. Finally, a complex rockslide example demon- strates the robustness and versatility of the coupled method.

FINITE ELEMENT ANALYSIS OF THERMOELASTIC BEHAVIOR OF PIEZOELECTRIC STRUCTURES UNDER FINITE DEFORMATION

It is noted that the behavior of most piezoelectric materials is temperaturedependent and such piezo-thermo-elastic coupling phenomenon has become even more pronounced in thecase of finite deformation. On the other hand, for the purpose of precise shape and vibrationcontrol of piezoelectric smart structures, their deformation under external excitation must beideally modeled. This demands a thorough study of the coupled piezo-thermo-elastic response underfinite deformation. In this study, the governing equations of piezoelectric structures areformulated through the theory of virtual displacement principle and a finite element method isdeveloped. It should be emphasized that in the finite element method the fully coupledpiezo-thermo-elastic behavior and the geometric non-linearity are considered. The method developedis then applied to simulate the dynamic and steady response of a clamped plate to heat flux actingon one side of the plate to mimic the behavior of a battery plate of satellite irradiated under thesun. The results obtained are compared against classical solutions, whereby the thermal conductivityis assumed to be independent of deformation. It is found that the full-coupled theory predicts lesstransient response of the temperature compared to the classic analysis. In the steady state limit,the predicted temperature distribution within the plate for small heat flux is almost the same forboth analyses. However, it is noted that increasing the heat flux will increase the deviationbetween the predictions of the temperature distribution by the full coupled theory and by theclassic analysis. It is concluded from the present study that, in order to precisely predict thedeformation of smart structures, the piezo-thermo-elastic coupling, geometric non-linearity and thedeformation dependent thermal conductivity should be taken into account.

Influence of underground water seepage flow on surrounding rock deformation of multi-arch tunnel

Based on a typical multi-arch tunnel in a freeway, the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) was used to calculate the surrounding rock deformation of the tunnel under which the effect of underground water seepage flow was taken into account or not. The distribution of displacement field around the multi-arch tunnel, which is influenced by the seepage field, was gained. The result indicates that the settlement values of the vault derived from coupling analysis are bigger when considering the seepage flow effect than that not considering. Through the contrast of arch subsidence quantities calculated by two kinds of computation situations, and the comparison between the calculated and measured value of tunnel vault settlement, it is found that the calculated value(5.7-6.0 mm) derived from considering the seepage effect is more close to the measured value(5.8-6.8 mm). Therefore, it is quite necessary to consider the seepage flow effect of the underground water in aquiferous stratum for multi-arch tunnel design.