开采扰动区断层采动活化诱发岩体动态变形模型实验

开采扰动区断层采动活化是诱发动力学灾害的典型难题之一。断层采动活化诱发岩体动态变形规律研究是揭示煤岩体结构、应力与力学行为对灾害控制作用的基础前提。通过对物理相似模型实验和声发射、应力与变形指标监测,揭示开采扰动区断层下盘、断层附近及断层上盘随工作面推进覆岩运移和矿压显现规律。实验研究表明:断层存在破坏了煤层顶板及上覆岩层的整体连续性,工作面矿压及上覆岩层垮落规律表现异常,断层极易活化,滑移现象明显;断层活化诱发上覆岩层发生整体切落,对工作面前方煤体产生很高的集中应力载荷,易诱发动力灾害。这为采动岩体动态断裂失稳和突水等灾害预报与调控提供理论依据。

小湾水电站坝基岩体质量动态评价研究

岩体质量随其赋存条件的变化而动态变化,因而坝基岩体质量的动态评价对于大坝工程的安全运营意义重大。本文以小湾水电站坝基岩体的大量测试、监测资料为基础,归纳总结了岩体质量的动态特征,提出了岩体质量劣化、恢复的评价指标,在常规岩体质量分级的基础上引入BQ系统、RMR系统动态评价岩体质量随四维空间的变化特征,建立了Vp-E0关系,并采用Hoek-Brown强度准则,确定各特征点的岩体强度指标。同时,以岩体松弛程度系数为指标,探讨了一种简易的岩体质量预测方法。

从施工地质灾害看岩体结构动态控制作用

在我国岩石工程规模加大、趋深而施工扰动范围趋广和趋强的今天,难以避让的不良地质体中常出现的施工地质灾害已成为影响工期和造价的极重要因素。工程实践观测到以不良地质体为主的岩体结构动态变化及其对快速、高强度工程开挖扰动的响应很复杂。理论上需认识不同层次和不同部位岩体变形破坏反映出的结构动态变化和调整,对其控制作用和工程调控需从相互作用时间变化角度加以表述,同时为"短进尺"等地下工程施工经验提供依据。通过总结、回顾岩体结构控制论发展和适用性,结合岩石工程中不良地质体有关的施工地质灾害防治实践,提出基于变形破坏时效性的岩体结构动态控制观(DDC)。以平行于背斜轴部展布的上公山隧洞围岩施工地质灾害导致工期延误和方案多次变更为例,说明岩体结构动态变化是工程施工扰动作用的集中体现和客观结果。本文结果或可为深入研究岩体变形破坏时效性提供一定地质基础。

工程地质综合性与岩体结构动态控制观的提出

当前我国一系列大型地质工程建设中地质灾害预报和动态设计、信息化施工的需求,使工程地质学面临综合理论创新发展的历史性机遇和挑战。有关学者提出大成综合理论,从源头上综合了专家的多源知识,从理论上凝炼了工程地质学高度综合的特点。以大成综合理论为基础,作者提出将众多因素相互作用进行观察、判断和测试,建立关系矩阵并加以权重分析和活跃强度等运算,提出了表征工程地质多因素作用关系简便可行途径。其研究难点在于综合认识地质条件的原生、次生和工程作用下的变化。总结复杂地质条件下国内外地质工程实践经验,提出了自然演化和工程扰动下岩体结构动态控制观(DDC)。结合工程场地规划和比选,以工程地质分区(EZI)、综合适宜性(CSI)、加固需求度(DRD)等可操作的量化指标,发展工程施工乃至运行扰动作用下的岩体结构控制论,更好地服务于地质工程与环境和谐的高层次决策目标。复杂地质条件下工程实践说明了DDC提出的科学合理性,以及解决复杂性问题的实用性。

基于应变率相关动力特性的岩体爆破破坏区范围研究

岩体动态强度特性及受力变化规律是研究炮孔近区岩体破坏特征的关键,采用合理的动态强度模型直接决定了炮孔破坏区范围计算结果的正确性。因此,利用理论分析与现场试验相结合的方法,研究了基于应变率相关动力强度特性下炮孔破坏区范围的计算方法。利用柱面波的位移协调方程,推导了炮孔近区岩体质点的应变率计算公式,并应用于岩体应变率相关的动抗压、抗拉强度准则;建立了岩体应变率相关的炮孔破坏区范围的计算模型,避免了因应变率参数的经验选取导致计算结果误差较大的问题。同时,利用实际工程中台阶爆破破坏区的实测结果,分析了不同孔径、装药条件下岩石底部残孔的破坏特性,并对不同破坏区的范围进行了测量及统计。由实测统计数据与计算结果的对比分析可知,不同孔径及装药条件下粉碎区、破碎区及裂隙区的理论计算结果与试验统计结果均较为接近,验证了不同条件下计算模型的准确性。研究成果对实际工程爆破破坏区范围预测及数值模拟有重要的参考意义。

龙滩水电站左岸边坡工程地质研究及蠕变体B区岩体质量评价

蠕变体B区边坡位于龙滩水库上游侧,是典型的层状反倾岩质边坡。由于风化卸荷以及其他综合营力的作用,边坡已发生了明显的折断错滑变形,因而其稳定性受到极大关注。本文的目的是在研究边坡构造特征的基础上,从岩体质量的角度认识蠕变体B区边坡的稳定性,为进一步边坡定量、定性分析提供科学依据。同时本文还对现有的岩体质量评价方法进行了讨论,并提出了动态岩体质量评价方法的概念。

空心包体式钻孔三向应变计测试技术探讨

探讨了澳大利亚CSIRO型空心包体式钻孔三向应变计的测量技术,重点介绍了测量元件应变片的布置形式和利用围压加载试验成果修正原始解除应变实测值的方法。对解除应变实测值的修正提出了具体方法,由修正后的解除应变推算的地应力实测值更精确。在三峡工程永久船闸开挖完成后岩体应力动态变化测量中,具体分析了测量元件应变片黏贴部位和角度的误差所引起的地应力实测值的误差,具体实施了对解除应变实测值的修正,实测的岩体应力动态变化更符合工程实际情况。

三峡船闸区地应力测量和开挖完成后动态变化

为了给三峡工程设计提供可靠的第一手资料,在工程前期的地质勘测和岩石力学科研工作中,对三峡工程区域、尤其是永久船闸地区进行了大量的地应力测量与研究。在船闸区开挖完成后,对其地应力的动态变化进行了分析。叙述了永久船闸最高边坡的三闸首南北两坡的深钻孔地应力测量成果和对船闸地区地应力场剖析,以及工程开挖完成后岩体应力的动态变化。

Analysis of the Elastic-Plastic Dynamic Finite Element on a Jointed Rock Mass

Aim To study the elastic plastic dynamical constitutive relations about a jointed rock mass under explosion load and its computer simulation. Methods\ Stress history is taken into account and stresses will follow changes in time during a period of explosion load. According to the principle of static force balance, the corresponding nodal concentrated force is calculated and the nodal displacement is counted. The elastic plastic dynamic finite element equations are thus obtained. Results\ A finite element method is given for a jointed rock mass under explosion load. Conclusion\ The problem of large plastic deformation for jointed rock mass on blasting was efficiently resolved through dynamic finite element analysis and the range of damages by blasting simulated, and this pushes forward the problem to engineering practice.

Mechanical response of roof rock mass unloading during continuous mining process in underground mine

Taking the test stopes during continuous mining induced roof caving of Tongkeng ore-body No.92 as example, the calculation flow of unloading analysis was established. According to the unloading region division method of the affected zone theory, and the deterioration laws of mechanics parameters of unloading rock mass, the continuous mining process in underground mine was analyzed by the software MIDAS/GTS, the mechanical response of roof rock mass unloading was studied, and the differences were analyzed with the conventional simulation. The result shows that the maximum tensile stress, subsidence displacement and equivalent plastic strain of roof rock mass are 1.5 MPa, 20 cm and 1.5% in the unloading analysis, while 1.0 MPa, 13 cm and 0.9% in the conventional analysis. The values of unloading analysis, which are also closer to the actual situation, are greater than those of conventional analysis; the maximum step in continuous mining is 48 m, which shows that the induced treatment of the roof should be carried out after 2 mining steps

Stress initialization methods for dynamic numerical simulation of rock mass with high in-situ stress

In the context of deep rock engineering,the in-situ stress state is of major importance as it plays an important role in rock dynamic response behavior.Thus,stress initialization becomes crucial and is the first step for the dynamic response simulation of rock mass in a high in-situ stress field.In this paper,stress initialization methods,including their principles and operating procedures for reproducing steady in-situ stress state in LS-DYNA,are first introduced.Then the most popular four methods,i.e.,explicit dynamic relaxation(DR)method,implicit-explicit sequence method,Dynain file method and quasi-static method,are exemplified through a case analysis by using the RHT and plastic hardening rock material models to simulate rock blasting under in-situ stress condition.Based on the simulations,it is concluded that the stress initialization results obtained by implicit-explicit sequence method and dynain file method are closely related to the rock material model,and the explicit DR method has an obvious advantage in solution time when compared to other methods.Besides that,it is recommended to adopt two separate analyses for the whole numerical simulation of rock mass under the combined action of in-situ stress and dynamic disturbance.

Dynamic evolution of shear rate-dependent behavior of rock discontinuity under shearing condition

Rock blocks sliding along discontinuities can cause serious disasters,such as landslides,earthquakes,or rock bursts.The shear rate-dependent behavior is a typical time-dependent behavior of a rock discontinuity,and it is closely related to the stability of a rock block.To further study the shear rate-dependent behavior of rock discontinuities,shear tests with alternating shear rates(SASRs)were conducted on rock discontinuities with various surface morphologies.The dynamic evolution of the shear rate dependency was studied in detail based on the shear test results,and three stages were identified with respect to the shear stress and shear deformation states.The test results revealed that dynamic changes in shear stiffness and the energy storage abilities of the rock discontinuities occurred in relation to the shear rate-dependent behavior of crack growth,which increased with an increase in normal stress and/or the joint roughness coefficient.The stage of decreasing shear stiffness corresponded to a stage of noticeable shear rate-dependency,and the shear rate was found to have no influence on the initial crack stress.

Dynamic Instability of Tunnel in Blocky Rock Mass

The displacements and geometry of the rock blocks and the properties of the rock struc-ture play an important role in the stability of tunnels.Based on the key block model,the dynamic instability analysis of underground tunnel subjected to intensive short-time compressional wave was conducted.The instability of the tunnel caused by the spallation and the inertial effect was distin-guished.And the influence of the roof contour curvature of tunnel was also determined.

Dynamic-static coupling analysis on rockburst mechanism in jointed rock mass

A numerical code called RFPA-Dynamics was used to study the rockburst mechanism under dynamic load based on coupled static-dynamic analysis.The results show that dynamic disturbance has a very distinct triggering effect on rockburst.Under the dynamic load,rockburst is motivated by tensile stress formed by the overlapping of dynamic waves in the form of instantaneous open and cutting through of cracks in weak planes and pre-damaged areas.Meanwhile,the orientation of joint sets has an obvious leading effect on rockburst locations.Finally,a higher initial static stress state before dynamic loading can cause more pre-damaged area,thus leading to a larger rockburst scope.

3-D fracture network dynamic simulation based on error analysis in rock mass of dam foundation

Accurate 3-D fracture network model for rock mass in dam foundation is of vital importance for stability,grouting and seepage analysis of dam foundation.With the aim of reducing deviation between fracture network model and measured data,a 3-D fracture network dynamic modeling method based on error analysis was proposed.Firstly,errors of four fracture volume density estimation methods(proposed by ODA,KULATILAKE,MAULDON,and SONG)and that of four fracture size estimation methods(proposed by EINSTEIN,SONG and TONON)were respectively compared,and the optimal methods were determined.Additionally,error index representing the deviation between fracture network model and measured data was established with integrated use of fractal dimension and relative absolute error(RAE).On this basis,the downhill simplex method was used to build the dynamic modeling method,which takes the minimum of error index as objective function and dynamically adjusts the fracture density and size parameters to correct the error index.Finally,the 3-D fracture network model could be obtained which meets the requirements.The proposed method was applied for 3-D fractures simulation in Miao Wei hydropower project in China for feasibility verification and the error index reduced from 2.618 to 0.337.

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.

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.