孔隙含水稳定岩层中井壁变形规律研究

发布时间：2018-04-20 23:28

本文选题：孔隙水压 + 稳定岩层　；参考：《中国矿业大学》2017年硕士论文

【摘要】：随井筒埋深的不断增加,高压孔隙水破坏基岩段井壁的问题日益凸显。针对此类问题,本文结合现有研究成果,采用理论分析、数值模拟与物理模拟相结合的方法,研究孔隙含水岩层中井壁结构的水力荷载,进而得到孔隙含水稳定岩层中井壁变形规律,完善了含水稳定岩层中井壁结构的设计理论。成果如下:首先,研究了孔隙水压作用下井壁结构对等效水力荷载的影响。运用Abaqus自带的孔压单元建立了平面应变模型,分析获得了孔隙水压作用受井壁尺寸、弹性模量以及泊松比的影响:孔隙水压作用下井壁表面的等效水力荷载随围岩与井壁弹性模量的比值增大而减小,说明围岩的弹性模量越大,等效水力荷载越小;井壁结构越厚,等效水力荷载越大;围岩泊松比越大,等效水力荷载越大;研究表明,井壁弹性模量对等效水力荷载的影响最大,井壁尺寸影响次之,泊松比影响最小。其次,研究了孔隙水作用下井壁结构的受力状态。基于相似理论,建立了大型物理模型试验,还原井壁真实受力状态,模型试验中完成了地压以及孔隙水压的独立加载并通过测试及反演计算掌握了等效水力荷载的变化规律以及数值水平。井壁结构在稳定含水岩层中的受力主要包含孔隙水压力和地应力,相较于稳定的地应力,孔隙水压力往往有不同的表现形式。在不同的接触条件下,井壁结构受到的等效孔隙水压力往往差别很大:当围岩和井壁未剥离时,孔隙水压引起井壁结构的水力荷载显著低于静水压力,约为静水压力的30%。当井壁和围岩接触面存在剥离时,孔隙水会迅速充满剥离区,该区域井壁所受到的等效水力荷载近似等于静水压力。第三,研究了稳定含水基岩段井壁变形规律和破裂模式。稳定含水岩层中由于岩层自身具有较高的自承载能力,高压孔隙水成为造成井壁破坏的主要因素。围岩孔隙水压恢复过程中,井壁和围岩存在局部剥离,使得井壁变形在竖向和水平方向均呈现较大不均匀性,剥离处井壁承受较大的水力荷载并且成为“破坏弱面”。孔隙稳定含水岩层中井壁的破裂模式以局部渗水、破裂出水为主。本次研究中创新性地运用了分布式光纤测试手段,将分布式光纤测试系统运用于井壁的空间连续应变监测,提高了测试的精度、稳定性并大大减少了出线量,通过本次试验,积累了分布式光纤在大型岩土工程试验应用的经验,有利于进一步拓展分布式光纤测试系统的应用前景。最后,根据以上研究成果,提出对于稳定含水岩层中井壁结构的设计理论的有益结论:水力荷载是衬砌结构设计要考虑的关键因素,在保证井壁和围岩不剥离的情况下,水力荷载显著小于静水压力;矿井井壁的设计应具备合理的强度和刚度,既能保证足够的稳定性和围岩不剥离,又能显著降低高压孔隙水的影响;
[Abstract]:With the increasing of wellbore buried depth, the problem of high pressure pore water destroying the wall of bedrock is becoming more and more serious. In view of this kind of problem, combining with the existing research results, this paper uses the method of theoretical analysis, numerical simulation and physical simulation to study the hydraulic load of borehole lining structure in porous water-bearing rock formation. Furthermore, the deformation law of borehole lining is obtained, and the design theory of wellbore structure in water-bearing rock is improved. The results are as follows: firstly, the influence of borehole wall structure on equivalent hydraulic load under pore water pressure is studied. The plane strain model is established by using Abaqus's own pore pressure unit. The influence of elastic modulus and Poisson's ratio: under the action of pore water pressure, the equivalent hydraulic load of shaft wall surface decreases with the increase of the ratio of surrounding rock to wall elastic modulus, which indicates that the larger the elastic modulus of surrounding rock, the smaller the equivalent hydraulic load; The thicker the wall structure is, the greater the equivalent hydraulic load is, and the greater the Poisson's ratio of surrounding rock is, the greater the equivalent hydraulic load is. The study shows that the influence of wall elastic modulus on the equivalent hydraulic load is the greatest, the influence of shaft wall size is the second, and the influence of Poisson's ratio is the least. Secondly, the stress state of borehole wall structure under the action of pore water is studied. Based on the similarity theory, a large-scale physical model test was established to restore the true stress state of the shaft wall. In the model test, the independent loading of ground pressure and pore water pressure is completed, and the variation law and numerical level of equivalent hydraulic load are grasped by testing and inverse calculation. Pore water pressure and in-situ stress are mainly included in the stress of borehole wall structure in the stable water-bearing rock formation. Compared with the stable in-situ stress pore water pressure often has different forms. Under different contact conditions, the equivalent pore water pressure of borehole wall structure is often very different: when the wall rock and shaft wall are not stripped, the hydraulic load caused by pore water pressure is significantly lower than that of static water pressure, which is about 30 percent of hydrostatic pressure. When the contact surface between the wall and surrounding rock exists peeling, the pore water will fill the stripping zone quickly, and the equivalent hydraulic load on the sidewall in this area is approximately equal to the hydrostatic pressure. Thirdly, the sidewall deformation and fracture mode of stable water-bearing bedrock are studied. High pressure pore water is the main factor that causes the damage of borehole lining in stabilizing the water-bearing strata because of its high self-bearing capacity. In the process of pore pressure recovery of surrounding rock, there is a local exfoliation between the wall and surrounding rock, which makes the shaft wall deformation show greater heterogeneity in both vertical and horizontal direction, and the shaft wall at the stripping place bears large hydraulic load and becomes a "failure weak surface". The fracture mode of borehole lining in porous stable water-bearing rock is local seepage and rupture effluent. In this study, the distributed optical fiber testing method is innovatively used, and the distributed optical fiber testing system is applied to the spatial continuous strain monitoring of the shaft wall, which improves the accuracy, stability and greatly reduces the output of the line. The application experience of distributed optical fiber in large-scale geotechnical engineering test is accumulated, which is helpful to further expand the application prospect of distributed optical fiber test system. Finally, based on the above research results, a useful conclusion is put forward for the design theory of the lining structure in the stable water-bearing rock formation: hydraulic load is the key factor to be considered in the design of the lining structure, and under the condition that the lining and surrounding rock are not peeled off, The hydraulic load is obviously smaller than the hydrostatic pressure, and the design of the shaft wall should have reasonable strength and rigidity, which can not only guarantee sufficient stability and non-stripping of surrounding rock, but also significantly reduce the influence of high pressure pore water.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD262

【参考文献】