摘要:
本文尝试运用北京昌平十三陵钻孔98 m深度原地应力测量和实时监测数据,依据弹性力学应力张量叠加原理,计算得到不同时段地应力结果;根据断层滑动摩擦准则,探讨南口山前断裂活动性,对了解该区地震危险性有重要的意义。原地应力测量与实时监测计算结果表明:在2010年1月初和2013年3月31日,最大水平主应力平均值分别为5.30 MPa和7.56 MPa,呈增加趋势;最大水平主应力方向也由NNW逐渐过渡到NE至近EW向。断层面上剪应力与正应力的比值结果显示:在2010年1月初和2013年3月底,平均比值分别为0.12和0.22,虽均没有达到断层面临界滑动摩擦系数0.6,但其显示出的增加趋势在一定程度上反映了该地区构造活动有增强的迹象,该现象值得关注。
Abstract:
According to the elasticity of the stress tensors superposition principle, the authors calculated the stress state in different periods at the borehole drilled at Ming Tombs, Changping District, Beijing, attempting to apply the data obtained by in-situ stress measuring and monitoring. Based on the frictional sliding criteria, this paper deals with the sliding of piedmont Nankou fault near the borehole, which serves as an important implication for understanding the seismic hazard in this region. The in-situ stress results show that, at the stages of early January, 2010 and March 31, 2013, the average maximum horizontal principal stress was respectively 5.30 Mpa and 7.56 MPa, showing an increasing trend; the direction of maximum horizontal principal stress was gradually converted from NNW to NE-nearly EW. The ratio between shear stress and normal stress on the fault plane revealed that, at the stages of early January, 2010 and the end of March, 2013, the average ratio was respectively 0.12 and 0.22 at the depth of 98 m, which didn’t achieve the threshold sliding friction coefficient 0.6 of the fault. However, the increasing trend of the average ratio indicates that the tectonic activity in the region may increase to some extent. The phenomenon deserves further attention.
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