覆盖型岩溶塌陷模型试验与数值模拟研究

发布时间：2018-06-06 04:42

本文选题：覆盖型岩溶塌陷 + 塌陷机理　；参考：《合肥工业大学》2017年硕士论文

【摘要】：工程实践表明,野外覆盖型岩溶塌陷地质条件复杂,对地下水运移能力起重要作用的岩溶通道主要特征参数变化较大,溶洞开口大小也很难确定。由于现场试验存在着各方面限制,直接开展典型的标准系列试验以查清隐伏的岩溶通道特征和对应的塌陷状况难以实现。因此,在对安徽省沿江地区覆盖型岩溶塌陷发育现场调查的基础上,构造盖层-溶洞塌陷系统模型,开展模型试验模拟研究,归纳总结了区内岩溶塌陷的形成机理,进而采用三维数值模拟的方法,对水位下降致塌进行了数值模拟研究。本文安徽省沿江地区岩溶塌陷情况为研究背景,采用模型试验和数值模拟方法对岩溶塌陷临界水位降幅进行研究,以期为工程实践提供理论依据。主要得出了以下成果:(1)地下水位波动致塌,特别是水位下降致塌为主要致塌模式。人为开采地下水过程和矿山排水初期矿井突水引起的水位快速下降极易导致岩溶塌陷的发生,其致塌机理以潜蚀式塌陷为主,伴随真空负压效应。(2)提出水位下降过程中塌陷发生的临界水位降幅公式,利用正交试验原则设计四组覆盖型岩溶塌陷模型试验,对不同溶洞开口大小,覆盖层厚度和土体密实程度进行塌陷过程模拟。运用临界水位降幅实测数据对公式进行评价,验证结果表明所提出的计算临界水位降幅的方法是可行的。(3)覆盖型岩溶塌的临界水位降幅与岩土体盖层的厚度、强度指标、岩溶的溶洞开口(土洞规模)半径、溶洞内气压大小、地下水位变化幅度和地下水流速等因素有关,其中溶洞开口大小是影响塌陷发生的关键因素。(4)在物理模型试验的基础上,采用数值模拟的方法进行对比。对每组模型试验塌陷的过程进行数值模拟计算,数值模拟得到的结果与实际符合较好。(5)铜陵朝山地区岩溶塌陷数值模拟计算结果表明:在一定的溶洞开口大小范围内,随着溶洞直径增大,临界水位降幅迅速减少;溶洞直径超出一定范围后,临界水位降幅降低速度减慢,此时需考虑其他岩溶塌陷影响因素对临界水位降幅的作用。
[Abstract]:The engineering practice shows that the geological conditions of overlying karst collapse are complex, the main characteristic parameters of karst channel which play an important role in groundwater migration capacity vary greatly, and the opening size of karst cave is difficult to determine. Due to the limitation of various aspects in the field tests, it is difficult to carry out the typical standard series tests directly in order to find out the characteristics of the concealed karst channels and the corresponding collapse conditions. Therefore, based on the field investigation of the overlying karst collapse in the area along the Yangtze River in Anhui Province, the model of caprock caverns collapse system is constructed, and the model test simulation is carried out, and the formation mechanism of karst collapse in this area is summarized. Furthermore, the three-dimensional numerical simulation method is used to simulate the collapse of water level. In this paper, the karst collapse situation along the Yangtze River in Anhui Province is studied by using model test and numerical simulation method to study the decrease of critical water level of karst collapse, in order to provide theoretical basis for engineering practice. The main results are as follows: 1) collapse caused by fluctuation of groundwater level, especially when the water level falls down as the main collapse mode. The process of artificial exploitation of groundwater and the rapid decrease of water level caused by mine water inrush in the early stage of mine drainage can easily lead to the occurrence of karst collapse, and the mechanism of collapse is mainly subsurface collapse. Following the vacuum negative pressure effect, the formula of critical water level decline occurred in the process of water level decline is put forward. Four groups of overlying karst collapse model tests are designed by using the principle of orthogonal test, and the opening sizes of different caverns are obtained. The collapse process is simulated by the thickness of overburden and the compactness of soil. The formula is evaluated by using the measured data of critical water level drop. The results show that the proposed method for calculating critical water level drop is feasible. The critical water level decrease of cover karst collapse and the thickness and strength index of rock and soil caprock are proved to be feasible. The karst cavern opening (soil hole size) radius, the pressure inside the karst cave, the variation of groundwater level and the groundwater velocity are related to each other, among which the cavern opening size is the key factor affecting the collapse, which is based on the physical model test. The method of numerical simulation is used to compare. The numerical simulation of the collapse process of each group of model tests is carried out. The results obtained by numerical simulation are in good agreement with the actual results. The results of numerical simulation of karst collapse in Chaoshan area of Tongling show that: in a certain range of cave openings, the numerical simulation results show that, With the increase of cave diameter, the decrease of critical water level decreases rapidly, and when the diameter of cavern exceeds a certain range, the decreasing speed of critical water level decreases. At this time, the effect of other factors of karst collapse on critical water level decline should be considered.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P642.25

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