荷载对钻孔应变观测影响的实例分析

Example Analysis of Influence of Load on the Borehole Strain Observation

在对比分析地表集中荷载模型和三维有限线段荷载模型的基础上,结合张家口台钻孔体应变2012年1～5月短期异常变化时段受工程影响的实例,采用三维有限线段荷载模型定量计算清水河清淤和蓄水阶段对张家口体应变影响的理论值.结果表明：计算得到的张家口体应变理论值为-3.12×10-9、4.07×10-9,而实际扣除线性漂移后短期异常为-1.58×10-7、2.30 ×10-7,理论值远小于实测应变值,因此该项异常变化不能仅归结为工程建设造成的荷载变化所引起,可能存在其他干扰因素或地壳应变变化的共同作用.荷载对钻孔应变观测影响的定量计算,在钻孔应变资料异常分析判定中能起到-定的辅助作用.

On the basis of contrasting the surface concentrated load model and 3D finite line load model,combing with examples of short-term abnormal variation of borehole body strain recorded by Zhangjiakou Station from Jan.to May.,2012,we quantitatively calculate theoretical value of the borehole strain influenced by dredging and water storage of the Qingshui River by use of 3D finite line load model.The results show that the theoretical body strain are-3.12 × 10-9 and 4.07 × 10-9,but the short-term abnormal of body strain is-1.58 × 10-7 and 2.30 × 10-7 by removing linear drift,which means the theoretical strain value are far less than the actual measured values.Therefore the variation abnormal is not only caused by load fluctuation of engineering construction,but also by other confounding factors or crustal strain changes.Consequently quantitative calculating the influence of load on borehole strain,which can play an additional role in analyzing and determining abnormal borehole strain data.