裂隙岩体渗流与三维应力耦合的理论与实验研究

围绕裂隙岩体渗流与应力之间的关系问题,从理论出发,经过合理的建模和严密的推演,得出裂隙岩体渗流与三维应力的耦合方程。该方程经过了大量的三轴实验数据的验证,解决了裂隙岩体受到的侧向应力对其渗流是否有影响这一岩石力学学科中争议很大的问题。指出了裂隙侧向应力引起的裂隙侧向变形是影响裂隙岩体渗流的主要因素,其影响符合负指数规律。同时,还分析了裂隙组的渗流问题。

场地存在高陡自然边坡的岩土工程勘察

岩土工程勘察中,首先要考虑场地的整体稳定性,要消除场地周边现状存在的不良地质作用,评价项目建设中切填方可能引发的边坡稳定性,在工程实践中已得到广泛认可及应用。文章以思南县青岗坡中学整体搬迁项目为例,阐述了岩土工程勘察过程中场地存在高陡自然边坡时候的勘察处理方式及基础建议埋深,为类似工程借鉴和参考。

老采空区充水影响下覆岩移动规律研究

伴随着煤炭行业化解淘汰过剩落后产能,大量生产矿井将逐渐关闭,井下采空区将会被地下水充填,采空区充水后覆岩移动变形规律是绿色矿山建设关注的焦点问题。文中通过相似材料模拟试验对采空区充水后覆岩移动规律及力学特征进行了研究,研究结果表明,在采空区充水后水分向上运移,导水裂缝带的岩体遇水软化,孔裂隙进一步压实,岩体压力不断增加,下沉量增大;在开采区域外岩层出现了显现的上升现象;采空区充水后地表下沉值不会出现大幅增加或突然塌陷等地质灾害现象。

格构锚在无外倾结构面岩质边坡中的应用

格构锚是利用格构梁进行边坡坡面防护,并利用锚杆或锚索加以固定的一种加固技术,在岩质边坡支护设计中扮演着举足轻重的角色,在工程实践中已得到广泛应用。本文以思南县工业园区饶家坝边坡为例,阐述边坡区地质构造、水文地质条件、周边环境、岩土参数建议值和边坡基本情况,然后对其开展稳定性分析,设计边坡支护方案,以期为类似工程提供借鉴。

轴对称巷道变形的弹塑性理论分析

本文采用莫尔－库仑准则和非关联流动法则分析了轴对称巷道围岩的变形规律。从轴对称平面应变问题的基本方程出发，导出巷道变形的理想弹塑性位移解答，给出其适用条件和实例计算结果。

物探方法预测煤层顶底板稳定性的可行性分析

该文通过讨论不同煤性岩体在不同应力作用下电阻率的变化,来探讨岩体电阻率变化过程中的一些规律,以研究影响煤层顶板特性的一些岩体电阻率的参数,借以讨论运用物探的方法在预测回采工作面煤层顶板的稳定性中的一些问题。

高地压破碎带巷道支护方式探讨

本文探讨了地方国营煤矿高地压破碎带巷道的支护方式。

Micro-seismic wave's propagation law and its numerical simulation

Deduced the propagation rule of longitudinal and transverse wave. On the basis of this, propagation rules in attenuated visco-elastic media and varied Lame coefficient were put forward as well. The subsequent numerical analysis found that in a small scope longitudinal and transverse wave could be considered as homogeneously propagating when faultages and joints were not taken into account. The existence of lane hindered the wave＇s propagation, and it made the velocity gradient change in a local vicinity area. Therefore velocity varied in different direction.

The depth effect of geological mechanics and hydraulic behaviors of rock mass

Significant changes of geological and hydraulic behaviors of rock mass with depth was studied. The general regulation and the critical depth of qualitative change of rock mass geological and hydraulic changes with depth were studied. Preliminary research show that the mechanical properties of rock mass gradually change from solid to plastic with the increasing of its buried depth. The critical depth of this tendency was controlled by geological properties of rock mass and its overlying rock. The critical depths are different in different regions because of its different geological condition. The general change depth of rock mass from rigid property to plastic property in coal mine regions of North China is about 1 800-2 300 m. The hydraulic permeability of rock mass will change significantly with depth because of the geological and hydraulic mechanics changes from solid to plastic and the groundwater circulation condition in karst and fractured aquifer will also change. The results reflact that the stability, deformation, failure, permeability and groundwater hazardous condition of rock mass during deep mining process are quite different from that of shallow mining＇s.

Support pressure assessment for deep buried railway tunnels using BQ-index

Estimation of support pressure is extremely important to the support system design and the construction safety of tunnels.At present,there are many methods for the estimation of support pressure based on different rock mass classification systems,such as Q system,GSI system and RMR system.However,various rock mass classification systems are based on different tunnel geologic conditions in various regions.Therefore,each rock mass classification system has a certain regionality.In China,the BQ-Inex(BQ system)has been widely used in the field of rock engineering ever since its development.Unfortunately,there is still no estimation method of support pressure with BQ-index as parameters.Based on the field test data from 54 tunnels in China,a new empirical method considering BQ-Inex,tunnel span and rock weight is proposed to estimate the support pressure using multiple nonlinear regression analysis methods.And then the significance and necessity of support pressure estimation method for the safety of tunnel construction in China is explained through the comparison and analysis with the existing internationally widely used support pressure estimation methods of RMR system,Q system and GSI system.Finally,the empirical method of estimating the support pressure based on BQ-index was applied to designing the support system in the China’s high-speed railway tunnel—Zhengwan high-speed railway and the rationality of this method has been verified through the data of field test.

Pressure-relief effect of coal rock body of long distance lower protective seam mined based on FLAC^(3D)

According to the specific geological condition, analyzed the stress distribution of the overlying strata, the displacement of pressure released seam, thickness variation and the distribution of plastic zones by FLAG3D software to simulate mining of the long-distance lower protective seam. The research results show that the distribution of vertical stress appears as a ＂Double-hump＂ within the pressure-relief range of the protected coal seam and the swelling deformation curve of coal bodies takes an ＂M＂ shape. The swelling is divided into initial swelling, swelling increase and swelling compression stability. The maximum swelling ratio of the pressure released seam is 1.84%, protection angle of the lower protective coal seam along the strike direction is about 55°, protection angle below the dip direction is about 50°, protection angle above the dip direction is about 55°, and the coal seam compression zone resembles a ＂U＂ shape.

Piezoelectric responses of brittle rock mass containing quartz to static stress and exploding stress wave respectively

The electromagnetic emission(EME) induced from the rock containing piezoelectric materials was investigated under both static stress and exploding stress wave in the view of piezoelectric effect. The results show that the intensity of the EME induced from the rock under static stress increases with increasing stress level and loading rate; the relationship between the amplitude of the EME from the rock under different modes of stress wave and elastic parameters and propagation distance was presented. The intensity of the EME relates not only to the strength and elastic moduli of rock masses,but also to the initial damage of the rock. The intensity of EME induced by stress wave reaches the highest at the explosion-center and attenuates with the propagation distance. The intensity of EME increases with increasing the elastic modulus and decreases with increasing initial damage. The results are in good agreement with the experimental results.

Stresses induced by post-tensioned anchor in jointed rock mass

A new analytical study on stresses around a post-tensioned anchor in rocks with two perpendicular joint sets is presented. The assumptions of orthotropic elastic rock with plane strain conditions are made in derivation of the formulations. A tri-linear bond-slip constitutive law is used for modeling the tendon-grout interface behavior and debonding of this interface. The bearing plate width is also considered in the analysis. The obtained solutions are in the integral forms and numerical techniques that have been used for evaluation. In the illustrative example given, the major principal stress is compressive in the anchor free zone and compressive stress concentrations of 815 k Pa and 727 k Pa(for the anchor load of 300 k N) are observed under the bearing plate and the bond length proximal end, respectively. However, large values of tensile stresses with the maximum of-434 k Pa are formed at the bond length distal end. The results obtained using the proposed solution are compared very those of numerical method(FEM).

Mechanical Response of Saturated Geological Rock Mass under Tidal Force

In this paper, the mechanical response of saturated geological rock under tidal force is explored by poroelastic theory. First, we use the free energy formula of saturated rock under a tidal force to study the relationships of pore pressure with stress, and stress with strain. Then we analyze the relationship between rock strain and tidal potential by the equilibrium differential equations of saturated rock under tidal force. Finally, we derive the physical relationship between the two parameters （pore pressure and tidal mean stress） of saturated rock and tidal potential. The relationship shows that：pore pressure is directly proportional with tidal potential, but tidal mean stress of saturated rock is inversely proportional with tidal potential. The ratio coefficient is related not only to the Lame coefficients of rock skeletons, but also to the Blot modulus. By using this model to analyze observational well water level of C-18 well which locates in Huili, Sichuan Province, the well level response coefficient （D） was estimated. This way, we derive the Skempton coefficient （B）, the coefficient A and C which refer to the response coefficients of pore pressure and tidal stress to tidal potential respectively. Then we compare the differences among each coefficient in coupling and uncoupling conditions. It shows that for saturated rocks, the response of stress and pore pressure to earth tides is a product of coupling, and it is necessary to take into account the coupling effect when we study the mechanical response. The model will provide the basis not only for the study of mechanics and hydrodynamics of well-confined aquifer systems, and the mechanics of faulting under tidal force, but also for quantitative research of the triggering mechanism of tidal forces.

Effect of fissure water on mechanical characteristics of rock mass

In view of the effect of fissure water in fractured rock mass on the strength of rock mass in engineering projects, we pre-pared specimens of cement mortar to simulate saturated rock mass with continuous fractures of different slope angles. By exerting static and dynamic loads on the specimens, the mechanical characteristics of rock mass with fissure water under these loads can be analyzed. Our experimental results indicate that the static compressive strength of saturated fractured rock mass is related to the slope angle. The lowest compressive strength of fractured rock mass occurs when the slope angle is 45°, while the highest strength occurs when the specimen has no fractures. Fissure water can weaken the strength of rock mass. The softening coefficient does not vary with the slope angle and type of load. The hydrodynamic pressure of fractured rock mass gradually increases with an increase in dynamic load. For a 0° slope angle, the hydrodynamic pressure reaches its highest level. When the slope angle is 90°, the hydro-dynamic pressure is the lowest.

STUDY ON FRACTURE AND MOVEMENT OF OVERLYING BEDROCK IN SHALLOW SEAM UNDER THICK SAND

Based on the field observation results of ground pressure in shallow seam, the movement characteristics of overlying strata in front and behind and the subsidence of the earth’s surface are studied. Also, the paper analyzes the stability of overlying bedrock according to the theory of voussoir beam’s "S-R" stability and the hypothesis of step subsidence. It points out that slide instability is the fundamental form of overlying bedrock movement.

FEM analyses for influences of stress corrosion and pressure solution on THM coupling in dual-porosity rock mass

With the models of stress corrosion and pressure solution, by Yasuhara et al., two computation conditions were designed for a hypothetical nuclear waste repository in an unsaturated dual-porosity rock mass: (i) the fracture apertures are changed with the stress corrosion and pressure solution (the porosity of rock matrix is also a function of stress); (ii) the fracture apertures and the porosity of rock matrix are constants. Then the corresponding two-dimensional FEM analyses for the coupled thermohydro-mechanical processes were carried out, and the states of temperatures, rates and magnitudes of aperture closure, pore pressures, flow velocities and stresses in the rock mass were investigated. The results show the followings: The aperture closure rates caused by stress corrosion are almost six orders higher than those caused by pressure solution, and the two kinds of closure rates climb up, then decline, furthermore tend towards stability; the fracture apertures decrease from the original value and tend towards the residual value, and the contact-area ratios of asperities increase also from the original value and tend towards the nominal value; when the effects of stress corrosion and pressure solution are considered, the negative fracture pressures in near field rise very highly; the differences between the magnitudes and distributions of stresses within the rock mass in two calculation cases are very small.