孤石爆破对土体扰动规律的试验研究

Experimental Study on Disturbance under Boulder Blasting

土层中存在球状风化花岗岩类孤石时,给盾构法地铁施工带来困难。对于探明位置的此类孤石大多采用爆破进行处理,爆破后会对一定范围的土层产生扰动。采用模型试验的方法,通过检测土体密度、含水率和抗剪强度在爆破前后的变化规律来揭示爆破扰动的范围。结果表明：这些土体物理—力学指标随爆心距呈现波动性变化,压密系数为1.045~1.090,含水率增大量为4%~12%,抗剪强度增大约为6%~19%;粘性土在含水率为21%情况下所产生的扰动最大,扰动最大位置在1倍试件边长处,扰动范围为2倍试件边长。

When the boulder of spherical weathering granite is in soil, great difficulty in shield excavation will produce. The blasting was used to dispose of these bou｜ders by position detection ,which will cause disturbance on the certain range soil. The model test was also used to detect the law of change in soil under blasting, including density, moisture content and shear strength. The results show that these physical and mechanical indexes show fluctuating changes with blast center distance,with the coefficient of compaction range 1. 045 - 1. 090, the increase amount of moisture content range 4% - 12% and the increase amount of shear strength range 6% - 19%. Cohesive soil has the maximum disturbance under the moisture content 21%. The position of maximum disturbance is at 1 times length of test specimen, and the range of disturbance is 2 times length of test specimen.