可溶岩矿原位溶浸开采沉陷机理研究

In process of in-situ dissolution mining, dissoluable rock mineral can form cavity via rock dissolution，the supporting effect of rock on overlying strata is reduced gradually with development of cavity. Overlying strata bend downwards and this can lead ground to subsidence. The integrated methods, i.e. site surveys, theoretical analyses, experiments, and numerical simulations are used in the project. Model is established followed with its practical utilization to study effect laws of mineral deformation on overlying strata creep of glauberite, a sort of dissolvable rock mineral, under different mining conditions. Experiment is to study creep laws along direction vertical to glauberite beddings under coupling effect of osmotic pressure, density and temperature of the leaching solution. Moreover, specimens are conducted for micro CT scanning before and after creep experiment. Creep laws of typical overlying glauberite strata during cavity evolution are investigated through the experiments. Based on the experimental data and theoretical analyses, creep constitutive model is established, subsidence law is simulated and the mechanism of subsidence is analyzed. The results are put into application in glauberite production mines located in Meishan, Sichuan Province. The mechanism and rules of subsidence during in-situ dissolution mining are investigated from perspective of rock mechanics, by which subsidence projection model is constituted in in-situ dissolution mining.

可溶岩矿原位溶浸开采过程中矿体溶解形成溶腔，随着溶腔不断演化，逐渐失去对上覆岩层的支撑作用。在自重力作用下，上覆岩层产生向下弯曲变形导致地面沉陷。项目采用现场调研、理论分析、试验研究、数值模拟及模型建立、现场应用相结合的方法，研究钙芒硝可溶岩矿原位溶浸开采过程中不同开采条件下矿体及上覆岩层变形对沉陷的影响规律。试验研究溶浸液渗透压、浓度、温度耦合作用下钙芒硝可溶岩垂直层理的蠕变规律，并对蠕变前后钙芒硝试件进行显微CT扫描观测，试验研究钙芒硝矿上覆典型岩层在溶腔演化过程中的蠕变规律。通过试验数据和理论分析，建立蠕变本构模型，模拟沉陷规律，分析沉陷机理。在四川眉山区钙芒硝生产矿井进行现场应用，从岩石力学的角度分析原位溶浸采矿沉陷的机理规律，建立原位溶浸采矿沉陷预计模型。

为了掌握钙芒硝盐岩原位开采过程中溶腔的稳定性和地面沉降情况，本项目完成了轴压5 MPa、围压4 MPa、不同渗透压（3，2，1 MPa）、不同温度（30，60，90 ℃）条件下的三轴蠕变试验，并在试验前后对试件进行CT扫描，研究了在温度-溶浸-应力耦合作用下，钙芒硝盐岩蠕变的温度效应，分析了不同渗透压条件下温度对钙芒硝不同蠕变过程蠕变变形的影响。结果表明：溶浸连通过程，对钙芒硝盐岩蠕变变形起主要作用的是渗透压和温度，渗透压越小，温度越高，蠕变变化量越大；饱水蠕变过程，温度和有效应力是影响蠕变变形特性的主要因素，随温度的升高蠕变变化量逐渐增大，但增加幅度逐渐减小，在72h的蠕变过程中，渗透压为2 MPa时，30 ℃~60 ℃与60 ℃~90 ℃的蠕变变化量分别增加52 %，35%，渗透压为3 MPa时，分别增加200 %，133 %；排水蠕变过程，影响钙芒硝蠕变变形的主要因素是温度和溶浸-应力-温度作用的历史过程对钙芒硝固体骨架力学性能的弱化程度，随温度的升高蠕变变化量和增加幅度都逐渐增大，在72h的蠕变过程中，在渗透压为2 MPa时，30 ℃~60 ℃与60 ℃~90 ℃的蠕变变化量分别增加47 %，60%；基于非线性流变力学理论，对广义开尔文模型进行非线性改进，根据蠕变试验结果，采用曲线拟合法对改进后模型的参数进行反演识别。发现与实测数据吻合效果良好，说明改进后的模型可以较好的描述钙芒硝在温度-溶浸-应力耦合作用下的排水蠕变过程。