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针对浅表高水平地应力和高侧压系数常出现在岩浆岩和变质岩中的现象,以广泛分布的形成于地下深处的花岗岩为例,指出构造隆升作用下,花岗岩从形成时位于深部到现在处于剥蚀卸荷过程中而常出露地表,无论是采用静水压力还是弹性体假设,都可得出其侧压系数明显变大的结论。对254组花岗岩地应力现场实测结果统计,得到了侧压系数拟合公式更符合花岗岩实测结果分布情况。由广义虎克定律出发,结合垂向卸荷后地下某处水平应变为0的假设,推导出花岗岩体剥蚀厚度计算公式,其结果接近目前为止认识到的剥蚀厚度的上限值。初步工程资料分析对比发现,大亚湾燕山期花岗岩地质分析剥蚀厚度为1 300 m,计算结果介于1 500～3 000 m之间;三峡工程船闸区花岗岩剥蚀厚度为1 700～3 200 m,与裂变径迹法测试结果比较吻合。结果说明,花岗岩体剥蚀厚度相对于现在一般工程埋深是比较大的。
Aiming at the phenomena that high surface stress and high lateral pressure coefficient are often found in magmatic rocks and metamorphic rocks, taking the widely distributed granite formed in the deep underground as an example, it is pointed out that under the tectonic uplift, Deep to the present in the process of denudation unloading and often exposed surface, whether it is the use of hydrostatic pressure or elastic body assumptions, can be drawn its lateral pressure coefficient significantly larger conclusions. On the basis of field measurement results of 254 sets of granite ground stress, the fitting formula of lateral pressure coefficient is more in line with the distribution of measured results of granite. Based on the assumption of generalized Hooke’s law and the assumption that the horizontal strain at somewhere in the vertical direction is zero after vertical unloading, the formula for calculating the eroded thickness of granite body is deduced. The result is close to the upper limit of eroded thickness recognized so far. The comparison of preliminary engineering data shows that the thickness of the Yanshanian granite in the Daya Bay is about 1 300 m, and the calculated result is between 1 500 and 3 000 m. The thickness of granite erosion in the Three Gorges Project lock area is 1 700-3 300 m, The track test results are in good agreement. The results show that the granite body erosion thickness relative to the current general engineering depth is relatively large.