裂隙非饱和渗流及摩擦滑动特性研究

发布时间：2018-05-01 06:37

本文选题：裂隙 + 非饱和渗流　；参考：《浙江大学》2014年博士论文

【摘要】：裂隙非饱和渗流及摩擦滑动特性研究属基础性研究,同时其研究成果又能应用于工程建设、油气开采、地热开发和地震预警等领域。裂隙非饱和渗流和摩擦滑动特性研究的关键在于精确试验系统的搭建和高仿真数值模型的建立。本文以粗糙裂隙为主要研究对象,通过数值试验和物模试验研究裂隙的非饱和渗流以及摩擦滑动特性,主要研究内容和结果归纳如下： 1、通过分形理论构建粗糙裂隙面,错距合并两分形裂隙面并调整得到一定开度分布的单裂隙,然后进行单裂隙非饱和渗流数值模拟。模拟结果表明,排水曲线和吸水曲线之间存在迟滞现象,排水过程滞后于吸水过程；同时在数值模型中考虑裂隙-岩块间的拟稳态水交换,水交换明显影响裂隙的渗透性；通过进一步的参数敏感性分析表明：对裂隙渗透性影响最大的是岩块的渗透性,其次是岩块的初始饱和度,最小的是岩块孔隙率,其影响基本可忽略。 2、研制出一套模拟降雨在单裂隙-基质内入渗的试验装置,随后进行非饱和降雨入渗试验,观测降雨在裂隙和基质内的流动与分布以及裂隙-基质间的水力联系,分析水力联系对基质和裂隙非饱和水力参数的影响。试验结果发现：基质是降雨入渗的主要通道,裂隙成为隔断相邻基质间水力联系的屏障；但裂隙-基质间存在水力交换：裂隙内的毛细阻力导致降雨在裂隙上端累积,一部分累积水流由两侧进入基质,成为基质额外的水源,因此加速了基质的饱和进程,而延缓了裂隙的饱和进程；同时,随着降雨在基质的入渗,裂隙-基质间存在水交换,水交换由湿润基质向干燥裂隙方向进行。通过比对试验还发现,裂隙开度的增大也会加速基质的饱和。最后成功用VG模型拟合得到基质和裂隙的持水特征曲线(毛细压力与体积含水率的关系曲线)。 3、搭建三轴试验系统,对劈裂石灰岩裂隙进行剪切滑动试验。首先进行干、湿试样滑动-控制-滑动(SHS)试验,研究裂隙摩擦强度在控制状态和滑动状态下的演变过程。通过滑动-控制-滑动试验发现：裂隙摩擦强度在控制时段内出现明显的下降,重新滑动后强度迅速愈合,呈现明显的时间依赖性；摩擦强度降低量和愈合量与控制时长成正比,而与有效应力成反比；水的作用则体现出两面性：一方面是水与磨损物发生胶结作用,使愈合量增加,另一方面水将磨损物冲出裂隙,使愈合量减小。 4、实施速度步长(VS)试验,滑动速度介于1-6μm/s,研究裂隙的滑动稳定性。速度步长试验结果表明：石灰岩裂隙摩擦强度随速度递增而稳步增长,呈现速度强化特性,滑动属稳定滑动。最后用固定水压渗透裂隙进行渗透试验,通过渗透试验观察到,裂隙渗透性不仅随有效应力递增迅速下降,而且在各级有效应力下渗透性亦随滑动逐渐减小,说明裂隙在滑动过程中继续闭合,并计算得到相应的裂隙闭合速率。 5、建立压力溶解模型和应力腐蚀模型模拟试验中观察到的摩擦强度愈合现象,分析溶解、沉降、扩散和微裂纹扩展过程对裂隙面的改造和计算相应的裂隙接触面积增长率。对比模拟结果(接触面积增长率)和试验结果(摩擦强度愈合量)发现,压力溶解模型低估短控制时间内(1000s)的愈合量,随控制时间增长模拟值逼近试验值,但整体模拟精度不高；加入应力腐蚀模型后,模拟结果改善明显,不仅提高了短控制时间内的模拟值,模拟值与试验值的变化过程也趋于一致。
[Abstract]:The research on unsaturated seepage and frictional sliding characteristics of fissure is a basic study, and its research results can also be applied to engineering construction, oil and gas exploitation, geothermal development and earthquake early warning. The key to the research of fracture unsaturated seepage and frictional sliding characteristics lies in the construction of accurate test system and the establishment of high simulation numerical model. Rough fissure is the main research object. Through numerical test and model test, the unsaturated seepage and frictional sliding characteristics of cracks are studied. The main contents and results are summarized as follows:
1, the fractal theory is used to construct the rough fissure surface, the error distance is combined with the split surface, and the single fissure is adjusted to a certain extent. Then the numerical simulation of the unsaturated seepage of the single fissure is carried out. The simulation results show that there is a hysteresis between the drainage curve and the water absorption curve, and the drainage process is lagging behind the water absorption process; at the same time, the numerical model is used in the numerical model. Considering the quasi steady water exchange between the crack and the rock mass, the water exchange obviously affects the permeability of the fissure. Through further parameter sensitivity analysis, it is shown that the permeability of the rock mass is the most affected by the fracture permeability, the second is the initial saturation of the rock block, and the minimum is the rock mass porosity, and the effect is basically negligible.
2, a set of experimental equipment to simulate rainfall in a single fissure matrix infiltration was developed, and then the unsaturated rainfall infiltration test was carried out to observe the flow and distribution of rainfall in the fracture and matrix, and the hydraulic relation between the fracture matrix and the fracture matrix. The influence of hydraulic connections on the unsaturated hydraulic parameters of the matrix and fracture was analyzed. The main channel of rainfall infiltration, the fracture becomes the barrier between the hydraulic connections between adjacent matrices, but there is a hydraulic exchange between the cracks and the matrix: the capillary resistance in the crack leads to the accumulation of rain in the upper end of the fissure, and a part of the accumulated water flows from both sides into the matrix and becomes the extra water source of the matrix, thus accelerating the saturation process of the matrix. At the same time, with the infiltration of the rain in the matrix, there is water exchange between the fracture matrix and the water exchange from the wetting matrix to the dry fissure. It is also found that the increase of the crack opening also accelerates the saturation of the matrix through the comparison test. Finally, the water holding characteristics of the matrix and the fissure are obtained by the VG model. Curves of capillary pressure and volume moisture content.
3, a three axis test system was set up to carry out a shear slide test on split limestone fracture. First, the dry, wet sample sliding control sliding (SHS) test was carried out to study the evolution process of the fracture friction strength under the control state and sliding state. Through sliding control sliding test, the fracture friction strength appeared obvious during the control period. Down, after sliding, the strength quickly healed and showed a distinct time dependence; the amount of friction and the amount of healing were proportional to the control, but inversely proportional to the effective stress; the action of water reflected the two sides: on the one hand, the water was cemented with the abrasive, increased the healing and washed the wear out of the water on the other. The gap reduces the amount of healing.
4, the velocity step length (VS) test was carried out, the sliding velocity was 1-6 Mu and the sliding stability of the crack was studied. The velocity step test results showed that the frictional strength of the limestone increased steadily with the increase of velocity, showing the velocity strengthening characteristic, and the sliding belonged to steady sliding. Finally, the seepage test was carried out with the fixed water pressure seepage fracture, through the penetration test. It is observed that the permeability of fissure not only decreases rapidly with the increase of effective stress, but also decreases with the sliding of the effective stress at all levels, indicating that the fracture continues to close during the sliding process, and the corresponding closing rate of the crack is calculated.
5, the frictional strength healing phenomenon observed in the pressure dissolution model and the stress corrosion model was established, and the solution, settlement, diffusion and microcrack propagation process were reformed and the corresponding fracture contact area growth rate was calculated. The comparison simulation results (contact surface product growth rate) and the test results (the friction strength healing amount) were analyzed. At present, the pressure dissolution model underestimates the healing amount of the short control time (1000s), and the simulated value is approximated with the control time, but the overall simulation accuracy is not high. After adding the stress corrosion model, the simulation results are improved obviously, and the simulated values are not only improved in the short control time, but also the change process of the simulated value and the test value also tends to be consistent.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV139.1

【参考文献】