地下水位线倾斜的地面塌陷演化过程试验研究

Experiments on collapse evolution process of karst stratum with inclined groundwater level

为探究地下水位线倾斜情况下岩溶地面塌陷的演化过程,设计一种模拟地下水位倾斜致塌的试验装置。首先,以砂土为试验材料,考虑地下水位线倾斜角度及岩溶水位高度变化等因素,开展室内物理模型试验。其次,通过监测试验过程中孔隙水压力、竖向土压力、地表沉降量及岩溶通道渗流总量等数据,测绘塌陷体的空间形态,分析地面塌陷的演化过程。试验结果表明:距离岩溶通道孔口越近,土中的孔隙水压力降幅及水力梯度越大,加速了孔口附近土体的变形和破坏。岩溶水位下降会在土体内部形成降落漏斗,引起地下水渗流量的非线性增长。以临界土洞为界,岩溶地面塌陷可分为内部塌陷和地表塌陷2个阶段。随着地下水位线倾角的增大,岩溶通道的渗流强度减弱,土体内部偏压特征逐渐显著,且偏压条件会增强对土拱效应的削弱作用。塌陷体中心线向高水位侧的偏斜角度与地下水位线倾角呈正相关,其空间形态由漏斗状转为牛角状。最后,参考渗水条件下深埋隧道松动土压力的计算方法,对渗流作用下岩溶土洞顶部松动土压力进行求解,所得结果与实际试验数值较为吻合,具有一定的合理性和参考意义。

To investigate the evolution of karst ground collapse under the tilted water table line,an experimental device was designed to simulate the collapse caused by the tilted water table.Firstly,the indoor physical model tests were carried out with sandy soil as the test material,considering the angle of water table tilt and the change of karst water table height.Secondly,the evolution process of ground collapse was analyzed by monitoring the data of pore water pressure,vertical earth pressure,surface settlement and total seepage of karst channels during the tests,and mapping the spatial morphology of the collapsed body.The test results are drawn as follows.1)The closer the distance to the karst channel orifice,the greater the pore water pressure drop and hydraulic gradient in the soil,accelerating the deformation and damage of the soil near the orifice.2)The drop in karst water level will form a landing funnel inside the soil,causing a non-linear increase in the amount of groundwater seepage.3)Taking the critical soil hole as the boundary,karst ground collapse can be divided into two stages:the internal collapse and surface collapse.4)As the inclination of the water table line increases,the seepage intensity of the karst channel decreases,the internal bias characteristics of the soil body gradually become significant,and the bias conditions enhance the weakening effect on the soil arch effect.5)The angle of deflection of the centreline of the collapsed body towards the high water table is positively correlated with the inclination of the water table,and its spatial pattern will change from funnel-shaped to bull-horn-shaped.Finally,referring to the calculation method of loose soil pressure in the deep-buried tunnel under seepage conditions,the loose soil pressure at the top of the karst soil cavity under seepage flow is solved.The results obtained are in good agreement with the actual test values,which has certain reasonableness and reference significance.