温度梯度水分扩散系数对非饱和双重孔隙岩体中THM耦合影响的有限元分析

建立了一种饱和–非饱和遍有节理岩体的双重孔隙—裂隙介质热—水—应力耦合模型,并研制出相应的二维有限元程序。通过一个假定的位于非饱和双重孔隙—裂隙岩体中的高放废物地质处置库算例,就温度梯度水分扩散系数不同的三种工况,考察了岩体中的温度、孔隙水压力、饱和度、地下水流速和主应力的变化、分布情况。结果显示：各工况计算域中温度场及应力场基本相同, 当岩体温度梯度水分扩散系数较大时,近场的负孔隙水压力上升到很高的数值,负裂隙水压力有所下降,饱和度亦有相应的变化,当温度梯度水分扩散系数小到一定程度后,其影响也将逐渐消失。     

Pore pressure generation in a saturated sand layer subjected to a cyclic horizontal acceleration at its base

A compaction theory for saturated sand, of differential type, is applied to shear wave propagation through a layer induced by cyclic horizontal acceleration of its base. The compaction relation incorporates dependence on the pore fluid pressure, and in turn the pore pressure is related to the compaction through the elastic compression relations. An assumption of undrained flow, which will yield the maximum pore pressures, allows straightforward numerical solution of the simplified dynamic equations. A variety of results are computed for comparison with alternative predictions.     

饱和地基任意形状衬砌内部均布突加荷载作用下的动力响应

地下衬砌结构经常会受到内部动荷载的作用,内荷载引起的衬砌结构的动应力集中备受关注.论文利用波函数展开法和Laplace变换,推导了饱和土中突加荷载作用下衬砌结构和土体的位移、应力、孔压表达式.应用复变函数和保角变换,将任意形状边界映射为圆形边界,利用饱和土和衬砌结构的连续条件和边界条件,求得了任意形状衬砌结构的动力响应...     

Method to calculate fatigue fracture life of control fissure in perilous rock

Rupture and safety of perilous rock are dominated by control fissure behind perilous rock block. Based on model-Ⅰand model-Ⅱstress strength factors of control fissure under acting of weight of perilous rock, water pressure in control fissure and earthquake forces, method to calculate critical linking length of control fissure is established. Take water pressure in control fissure as a variable periodic load, and abide by P-M criterion, when control fissure is filled with water, establish the method to calculate fatigue fracture life of control fissure in critical status by contributing value of stress strength factor stemming from water pressure of control fissure in Paris's fatigue equation. Further, parameters (C and m) of sandstone with quartz and feldspar in the area of the Three Gorges Reservoir of China are obtained by fatigue fracture testing.     

基于声发射参量的不同深度灰岩塑性破坏识别研究

对某矿深部灰岩进行单轴压缩试验,测得试件破坏全过程的应力、应变和声发射参数。通过分析应力、应变和声发射参数之间的关系,可根据声发射振铃计数率的变化情况,将全过程分为三个阶段:第一阶段处于孔隙裂隙压密阶段,振铃计数率较多;第二阶段处于稳定变形阶段,声发射处于平静期;第三阶段岩石进入塑性变形阶段,振铃计数率明显增加。研究发现,深度越深,第一阶段终止时的应力水平越高;将声发射累计能率与累计振铃计数率的比值定义为能振比λ,λ的变化规律一定程度上反映出试件内部裂隙发展情况。研究λ的变化规律能够为识别岩体失稳提供依据,提高声发射技术监测预报的准确性。     

Rheology on the drawing zone in glass spinning

This paper describes the work carried out to investigate the pore pressures occurring in secondary consolidation. A theoretical approach and an experimental technique was developed in order to conduct the study. By considering compression to occur only due to water leaving the soil it was possible to derive an expression for the dissipation of pore pressure in the secondary phase. By further simplified assumptions which are based on experimental observations, the above general solution was reduced to a simple formula which predicted the observed behaviour of pore water pressures during secondary consolidation.     

Nonlinear motion equations for a non-Newtonian incompressible fluid in an orthogonal coordinate system

This paper describes the work carried out to investigate the pore pressures occurring in secondary consolidation. A theoretical approach and an experimental technique was developed in order to conduct the study. By considering compression to occur only due to water leaving the soil it was possible to derive an expression for the dissipation of pore pressure in the secondary phase. By further simplified assumptions which are based on experimental observations, the above general solution was reduced to a simple formula which predicted the observed behaviour of pore water pressures during secondary consolidation.     

Pore water pressures in secondary consolidation

This paper describes the work carried out to investigate the pore pressures occurring in secondary consolidation. A theoretical approach and an experimental technique was developed in order to conduct the study.By considering compression to occur only due to water leaving the soil it was possible to derive an expression for the dissipation of pore pressure in the secondary phase. By further simplified assumptions which are based on experimental observations, the above general solution was reduced to a simple formula which predicted the observed behaviour of pore water pressures during secondary consolidation.     

Rhéologie particulière des solutions de polymères en millieus poreux

This paper describes the work carried out to investigate the pore pressures occurring in secondary consolidation. A theoretical approach and an experimental technique was developed in order to conduct the study. By considering compression to occur only due to water leaving the soil it was possible to derive an expression for the dissipation of pore pressure in the secondary phase. By further simplified assumptions which are based on experimental observations, the above general solution was reduced to a simple formula which predicted the observed behaviour of pore water pressures during secondary consolidation.     

An extension of Reiner’s “Deborah Number” concept to a wide field of rheological investigations

This paper describes the work carried out to investigate the pore pressures occurring in secondary consolidation. A theoretical approach and an experimental technique was developed in order to conduct the study. By considering compression to occur only due to water leaving the soil it was possible to derive an expression for the dissipation of pore pressure in the secondary phase. By further simplified assumptions which are based on experimental observations, the above general solution was reduced to a simple formula which predicted the observed behaviour of pore water pressures during secondary consolidation.     

Comparison of the time-temperature superposition of the relaxation modulus and time-to-break of preswollen gels

This paper describes the work carried out to investigate the pore pressures occurring in secondary consolidation. A theoretical approach and an experimental technique was developed in order to conduct the study. By considering compression to occur only due to water leaving the soil it was possible to derive an expression for the dissipation of pore pressure in the secondary phase. By further simplified assumptions which are based on experimental observations, the above general solution was reduced to a simple formula which predicted the observed behaviour of pore water pressures during secondary consolidation.     

A SOLUTION OF COSINE PRESSURES ON A HOLLOW CYLINDER AND THE LIMIT WHEN k→0

A new stress function is found in this paper and then the problems of cosine pressures on a hollow cylinder are solved with the new stress function, which provides the basis for the solution of the problems of space symmetrical deformation of a hollow cylinder. When the pressures do not vary in the axial direction, that is, when k→0 the lame formulae can be deduced.     

Drawdown Induced Changes in Permeability of Coalbeds: A New Interpretation of the Reservoir Response to Primary Recovery

A model for pore pressure-dependent cleat permeability is presented for gas-desorbing, linear elastic coalbeds under uniaxial strain conditions experienced in producing reservoirs. In the model, changes in the cleat permeability of coalbeds, which are idealised to have a bundled matchstick geometry, is controlled by the prevailing effective horizontal stresses normal to the cleats. Variations in the effective horizontal stresses under uniaxial strain conditions are expressed as a function of pore pressure reduction during drawdown, which includes a cleat compression term and a matrix shrinkage term that have competing effects on cleat permeability. A comprehensive analysis has revealed that the shape of the stress – pore pressure curve is predominantly determined by the magnitude of recovery pressure and rebound pressure relative to the initial reservoir pressure. A total of five possible scenarios have been identified with regard to response of the horizontal stress function to reservoir drawdown. When applied to four coalbed wells at two separate sites in the fairway of the San Juan basin, the model predictions at one site, where the three wells have shown increased absolute permeability during gas production, are in excellent agreement with the published pore pressure dependent permeability changes that were obtained independently from history matching the field production data. At a separate site the model correctly predicts, at least qualitatively, a strong permeability rebound at lower drawdown pressures that has been inferred through history matching the production data. An analysis of the effects of initial reservoir pressure on the response of effective horizontal stress to drawdown was carried out, with reference to the range of pressure likely to be encountered in the San Juan basin. The implications of this in terms of pore pressure dependent permeability are discussed.     

循环荷载下硅藻土应变和孔压特性

针对嵊州硅藻土的高结构性及地基应力场的复杂多变，应用GDS 动三轴仪进行不同围压和不同循环应力比下的不排水循环加载试验，分析应力-应变滞回曲线演化、应变累积特性、回弹特性及孔压特性．研究表明：循环应力比及围压对原状硅藻土应变和孔压的发展规律影响明显，随着循环应力比的增加，滞回曲线由线性状态转变为非线性状态，且逐渐向x 轴倾斜，累计应变和回弹应变都随着循环应力比的增加而略微增加，但总应变基本小于2 %；残余孔压比随循环应力比增大而增大，范围为0.1~0.5．并且存在一个临界循环应力比，其值随有效围压的增大而减小，范围为0.8~2.2，当循环应力比大于该值时，试样内部产生一个破裂面迅速发生破坏．在相同循环应力比下，试样的应变随着有效围压的增大而增大．     

Reservoir fluid flow through vertical fracture of thick stratum with underlying fluid interface

An exact solution is obtained for the problem of steady-state filtration of a heavy dense incompressible fluid in a thin, infinitely deep, inclined reservoir having a crack of given depth along the reservoir rise. The region of filtration of the lighter liquid (oil) has an impermeable upper boundary in the form of a horizontal fault line. Below the filtration region there is a free boundary, below which lies the region of stationary fluid (bottom water). The interface of the fluids, the fissure profile, and the reservoir fluid flow rate are determined from the solution of the problem on the basis of the given parameters (permeability of the reservoir and of the material filling the fissure, viscosity of the filtering fluid, specific weight of the upper and lower fluids, depth of the fissure, pressure differential between a point at the fissure and a point at the interface of the fluids). In the case when the thin reservoir is a vertical filtering layer, the considered flow is interpreted as the motion of the reservoir fluid through a vertical fissure of a thick reservoir (half-space) in the presence of an underlying fluid interface. The problem is solved in finite form with the aid of known analytic functions using integrals of the Cauchy type. The fundamental solution is first found of the special problem of flow with a point singularity. The fundamental solution is also of independent importance as an extension of the solution of certain known problems [1–4].     

饱和土中球空腔的瞬态动力响应

采用工程上通用的饱和土力学模型,考虑流体与固全之间的耦合作用,利用Ｌａｐｌａｃｅ变换求解了饱和土中球空腔的瞬态动力响应问题,得到了变换域内的解析解,借助数值Ｌａｐｌａｃｅ换求解了饱和土中球空腔瞬态动力响应的位移、应力及孔压的变化规律,为分析地下结构瞬态动力响应提供了一种有效的方法,模型符合工程实际,有一定的工程应用价值。     

卸荷条件下粉质粘土变形性状研究

通过室内应力控制的三轴试验研究卸荷条件下土体的应力-应变关系和孔隙水压力变化特征,得到变形模量的确定方法。研究表明:在初始偏压应力固结条件下,无论是轴向压力保持不变而侧向压力不断卸荷,还是轴向压力和侧向压力同时卸荷,其应力-应变关系均表现为较好的双曲线函数关系。而且,侧向固结压力愈大,强度值愈大。在卸荷过程中,随剪切应力的增大和剪切应变的发展,土样呈现剪胀趋势并在后期产生较大的负孔隙水压力。不排水条件下由于负孔隙水压力的存在,土样的表观强度略有增大。     

Slow Motion of a Porous Sphere Translating Along the Axis of a Circular Cylindrical Pore Subject to a Stress Jump Condition

The coupled flow problem of an incompressible axisymmetrical quasisteady motion of a porous sphere translating in a viscous fluid along the axis of a circular cylindrical pore is discussed using a combined analytical–numerical technique. At the fluid–porous interface, the stress jump boundary condition for the tangential stress along with continuity of normal stress and velocity components are employed. The flow through the porous particle is governed by the Brinkman model and the flow in the outside porous region is governed by Stokes equations. A general solution for the field equations in the clear region is constructed from the superposition of the fundamental solutions in both cylindrical and spherical coordinate systems. The boundary conditions are satisfied first at the cylindrical pore wall by the Fourier transforms and then on the surface of the porous particle by a collocation method. The collocation solutions for the normalized hydrodynamic drag force exerted by the clear fluid on the porous particle is calculated with good convergence for various values of the ratio of radii of the porous sphere and pore, the stress jump coefficient, and a coefficient that is proportional to the permeability. The shape effect of the cylindrical pore on the axial translation of the porous sphere is compared with that of the particle in a spherical cavity; it found that the porous particle in a circular cylindrical pore in general attains a lower hydrodynamic drag than in a spherical envelope.     

Thermodynamic approach to effective stress in partially saturated porous media

The form of the equilibrium effective stress acting on the solid phase of a porous medium containing two immiscible fluid phases is derived. The derivation makes use of the postulation of the thermodynamics of the system at the macroscale, a scale on the order of tens of pore diameters. The postulation at this scale facilitates the identification of the fraction of the solid surface in contact with each fluid phase as being the appropriate coefficient weighting each of the fluid phase pressures analogous to the Bishop parameter. In addition, the curvature of the surface of the solid phases is shown to impact the pressure exerted on the solid phase by the fluid. For the special case of low saturations when the wetting phase may be considered to be present only as a film on the solid phase, the macroscale disjoining pressure is found to modify the equilibrium form of the effective stress. In addition to the equilibrium effective stress, which is related to the forces acting on the interface between the solid phase and the fluids, the appropriate relation between the fluid pressures at the fluid–fluid interface is obtained. This analysis leads to the expression for the capillary pressure as a function of the phase pressures and the disjoining pressure.