盐岩非线性流变性态及地下复杂溶腔变形数值分析

针对平顶山盐田盐岩层数多、单层厚度薄、泥岩夹层多的特点,建立等效复合单元代替互层状盐岩体,利用ABAQUS软件对马庄井田的地下溶腔进行三维数值模拟研究,探讨不同内压下,腔周塑性区围岩的非线性流变性态以及溶腔体积缩减规律。结果表明:(1)等效复合单元在稳态蠕变阶段具有较好的数值稳定性,泥岩能有效地限制黏塑性区范围以及围岩向洞内位移的发展;(2)在围压(8 MPa)作用下,互层状盐岩单元体基本呈现线性小变形特征,溶腔体积收缩率与蠕变持续时间均呈现最低值,分别为3%与2.5 a,随着内压增大(8~12 MPa),互层状盐岩单元体开始呈现非线性蠕变,但经过较短时间后(2.5 a)体积收缩率逐渐稳定至一较小值,约为3.5%,随着内压的迅速减小(≤4 MPa),腔周盐岩逐渐呈现非线性大变形特征,表现为稳态蠕变时间增长,蠕变速率增加,5 a后围岩蠕变仍在稳定增加;(3)塑性区围岩内的黏滞系数随时间普遍加大,体现了互层状盐岩在储气运行过程中越来越稳定的变形趋势,因此,实际运行时储气压力应控制在合理范围(4~12 MPa),尤其要减少在较小内压下的蓄气运行时间。

层状岩体边坡变形破坏模式及滑坡稳定性数值分析

论述了层状岩体的地质特征及其物理力学特征 ,在此基础上 ,归纳了层状岩体构成的边坡几种变形破坏模式 ,然后对边坡破坏后形成的滑坡进行了稳定性数值分析。最后得出一些结论及认识。

考虑应变软化的地下采场开挖变形稳定性分析

为了分析某大型地下采场开挖稳定性,利用FLAC3D同时考虑岩土体的应变软化特性,计算开挖过程中的变形和破坏情况。结果表明:随着开挖的进行,周围岩体的位移不断增大,开挖步1_3,2_3和4引起的位移增量最大;开挖步1_1～1_2引起主采场顶板破坏高度为40m左右,当开挖步为1_3时,顶板破坏高度达到80m左右;2_1和2_2开挖步引起的破坏区面积变化不大,而2_3开挖步引起破坏高度迅速增长,达到120m;开挖到第4步时,由于主采场与1和2采场空区相互贯通,破坏高度同样迅速增大,达到150m左右;此后,由于影响稳定性的开挖阶段结束,破坏高度增量减小,最终破坏高度为160m左右,得到的结果能够为工程实践提供指导。

Elastoplastic model for discontinuous shear deformation of deep rock mass

Deep rock mass possesses some unusual properties due to high earth stress,which further result in new problems that have not been well understood and explained up to date.In order to investigate the deformation mechanism,the complete deformation process of deep rock mass,with a great emphasis on local shear deformation stage,was analyzed in detail.The quasi continuous shear deformation of the deep rock mass is described by a combination of smooth functions:the averaged distribution of the original deformation field,and the local discontinuities along the slip lines.Hence,an elasto-plastic model is established for the shear deformation process,in which the rotational displacement is taken into account as well as the translational component.Numerical analysis method was developed for case study.Deformation process of a tunnel under high earth stress was investigated for verification.

Study on destressing technology for a roadway driven along goaf in a fully mechanized top-coal caving face

Based on the deformation characteristics of the roadways driven along goaf in fully mechanized top coal caving faces, the author considers that it is the key to ensure the stability of surrounding rocks of roadway driven along goaf to control the deformation during the period affected by mining. Considering the characteristics of the roadway layout in fully mechanized top coal caving faces, a technical scheme of destressing is put forward and the destressing effect is analyzed by using the software of Universal Distinct Element Code 3 0(UDEC 3 0).

Effective grouting area of jointed slope and stress deformation responses by numerical analysis with FLAC^(3D)

To study the grouting reinforcement mechanism in jointed rock slope, first, the theoretical deduction was done to calculate the critical length of slipping if the slope angle is larger than that of joint inclination; Second, the numerical calculation model was founded by FLAG^3D, so as to find the stress and deformation responses of rock mass in the state before and after grouting, the analysis results show that the range between the boundary of critical slipping block and the joint plane that passes the slope toe is the effective grouting area （EGA）. After excavation, large deformation occurs along the joint plane. After grouting, the displacements of rock particles become uniform and continuous, and large deformations along the joint plane are controlled; the dynamic displacement can re- flect the deformation response of slope during excavation in the state before and after grouting, as well as the shear location of potential slip plane. After grouting, the dynamic displacement of each monitoring point reaches the peak value with very few time steps, which indicate that the parameters of the joint plane, such as strength and stiffness, are improved; the stress field becomes uniform. Tensile area reduces gradually; whole stability of the slope and its ability to resist tensile and shear stress are improved greatly.

Numerical and Dimensional Analysis for Prediction of Line Heating Residual Deformations

Line heating process is a very complex phenomenon as a variety of factors affects the amount of residual deformations. Numerical thermal and mechanical analysis of line heating for prediction of residual deformation is time consuming. In the present work dimensional analysis has been presented to obtain a new relationship between input parameters and resulting residual deformations during line heating process. The temperature distribution and residual deformations for 6 mm, 8 mm, 10 mm and 12 mm thick steel plates were numerically estimated and compared with experimental and published results. Extensive data generated through a validated FE model were used to find co-relationship between the input parameters and the resulting residual deformation by multiple regression analysis. The results obtained from the deformation equations developed in this work compared well with those of the FE analysis with a drop in the computation time in the order of 100 (computational time required for FE analysis is around 7 200 second to 9 000 seconds and where the time required for getting the residual deformation by developed equations is only 60 to 90 seconds).

Numerical Analysis of Finite Deformation of Overbroken Rock Mass in Gob Area Based on Euler Model of Control Volume

The overbroken rock mass of gob areas is made up of broken and accumulated rock blocks compressed to some extent by the overlying strata. The beating pressure of the gob can directly affect the safety of mining fields, formarion of road retained along the next goaf and seepage of water and methane through the gob. In this paper, the software RFPA＇2000 is used to construct numerical models. Especially the Euler method of control volume is proposed to solve the simulation difficulty arising from plastically finite deformations. The results show that three characteristic regions occurred in the gob area： （1） a naturally accumulated region, 0-10 m away from unbroken surrounding rock walls, where the beating pressure is nearly zero; （2） an overcompacted region, 10-20 m away from unbroken walls, where the beating pressure results in the maximum value of the gob area; （3） a stable compaction region, more than 20 m away from unbroken walls and occupying absolutely most of the gob area, where the beating pressures show basically no differences. Such a characteristic can exolain the easy-seeoaged “O”-ring phenomena around mining fields very well.

Numerical analysis of methane migration from floor strata to a longwall face

A two-dimensional numerical mine strata in the vicinity of seam 349 in model of a large （1 000 m× 200 m） section of Iongwall panel 802 in part B of the Murcki Colliery in the Upper Silesian Coal Basin, Poland, was built using the Universal Distinct Element Code UDEC. Longwall extraction of seam 349 with roof caving was simulated in the model over a length of 450 m. Mining-induced changes in displacements, strains and stresses in the mine strata were investigated. Under the assumptions that （1） methane-bearing strata occur 15.6 m beneath seam 349 and include seam 350 and the strata lying beneath, and （2） the methane reservoir pressure is equal to 2 MPa, a fully coupled mechanical hydraulic analysis was performed in which joint conductivity was dependent on the mechanical deformation and, conversely, the mechanical behavior of rock masses was affected by joint fluid pressure. It was shown that migration of methane from coal seams lying beneath the mined seam is possible under conditions where the floor strata deform to a great extent, undergo separation, fracture and break into blocks.

Numerical Analysis of Tensile Bifurcation Phenomenon of a Film Bonded to a Substrate

To study the mechanical properties of the film/substrate structure, the finite element code ABAQUS v6.9-1 is adopted to simulate the tensile mechanical behavior of the nanoscale thin film bonded to a substrate. The bifurcation phenomenon of the structure under uniaxial tension is found： the single-neck deformation, the multiple-neck deforma- tion and the uniform deformation. The substrate and the film are regarded as power-hardening materials obeying the J2 deformation theory. Firstly, the influence of material hardening match on tensile bifurcation mode is analyzed under perfectly well-bonded interface condition. Then, the effects of interfacial stiffness and other superficial defects sur- rounding the imperfection on bifurcation mode are investigated. It is concluded that under the well-bonded interface condition, if the stress of the substrate is larger than the film, the film will uniformly deform with the substrate; if the stress of the substrate is smaller than the film, the film will form a single neck, except the case that a weakly-hardening film is bonded to a steeply-hardening substrate when multiple necks can be formed. With the decrease of interracial stiffness, the uniform deformation mode can transform into the multiple-neck deformation mode, and further transform into the single-neck deformation mode. And other defects surrounding the imperfection can influence the wavelength of deformation and neck number.

A meshfree method and its applications to elasto-plastic problems

Standard finite element approaches are still ineffective in handling extreme material deformation, such as cases of large deformations and moving discontinuities due to severe mesh distortion. Among meshfree methods developed to overcome the ineffectiveness, Reproducing Kernel Particle Method (RKPM) has demonstrated its great suitability for structural analysis.This paper presents applications of RKPM in elasto-plastic problems after a review of meshfree methods and an introduction to RKPM. A slope stability problem in geotechnical engineering is analyzed as an illustrative case. The corresponding numerical simulations are carried out on an SGI Onyx3900 supercomputer. Comparison of the RKPM and the FEM under identical conditions showed that the RKPM is more suitable for problems where there exists extremely large strain such as in the case of slope sliding.

NUMERICAL MANIFOLD METHOD AND ITS APPLICATION IN UNDERGROUND OPENINGS

A brief introduction is made for the Numerical Manifold Method and its analysing process in rock mechanics. Some aspects of the manifold method are improved in implementing process according to the practice of excavating underground openings. Corresponding formulas are given and a computer program of the Numerical Manifold Method has been completed in this paper.

An improved three-dimensional spherical DDA model for simulating rock failure

In this paper, a discontinuous numerical model, namely SDDARF3D(three-dimensional spherical discontinuous deformation analysis for rock failure), is proposed for simulating the whole process of rock failure. Firstly, within the framework of the classical discontinuous deformation analysis(DDA) method, the formulation of three-dimensional spherical DDA(3D SDDA) is deduced; secondly, a bonding and cracking algorithm is constructed and the SDDARF3 D model is proposed; thirdly, corresponding VC++ calculation code is developed and some verification examples are calculated. The simulated results can intuitively reproduce the failure phenomena of rock mass, indicating that the proposed SDDARF3 D numerical model is correct and effective.

Discontinuous deformation and displacement analysis: From continuous to discontinuous

A discontinuous deformation and displacement(DDD) analysis method is proposed for modelling the rock failure process. This method combines the rock failure process analysis(RFPA) method(based on finite element method) and discontinuous deformation analysis(DDA) method. RFPA is used to simulate crack initiation, propagation and coalescence processes of rock during the small deformation state. The DDA method is used to simulate the movement of blocks created by the multiple cracks modelled by the RFPA. The newly developed DDD method is particularly suitable for modelling both crack propagation and block movement during the rock failure process because of the natural and convenient coupling of continuous and discontinuous deformation analyses. The proposed method has been used to simulate crack initiation, propagation and coalescence within a slope as well as the block movement during the landslide process. Numerical modelling results indicate that the proposed DDD method can automatically simulate crack propagation and block movement during the rock failure process without degrading accuracy.

Design and implementation of a software architecture for 3D-DDA

The three-dimensional discontinuous deformation analysis(3D-DDA) is a promising numerical method for both static and dynamic analyses of rock systems. Lacking mature software, its popularity is far behind its ability. To address this problem, this paper presents a new software architecture from a software engineering viewpoint. Based on 3D-DDA characteristics, the implementation of the proposed architecture has the following merits. Firstly, the software architecture separates data, computing, visualization, and signal control into individual modules. Secondly, data storage and parallel access are fully considered for different conditions. Thirdly, an open computing framework is provided which supports most numerical computing methods; common tools for equation solving and parallel computing are provided for further development. Fourthly, efficient visualization functions are provided by integrating a variety of visualization algorithms. A user-friendly graphical user interface is designed to improve the user experience. Finally, through a set of examples, the software is verified against both analytical solutions and the original code by Dr. Shi Gen Hua.