渤海海峡及周边地应力分布规律与应力积累研究

Geostress distribution and stress accumulation in Bohai strait and adjacent area

为研究渤海海峡及周边表层、浅表层地应力分布规律的异同及区域应力积累程度,以通道中轴线上布设的5个浅钻水压致裂数据为基础,结合收集的周边区域深钻数据,建立了海峡处表层、周边区域浅表层应力参数随深度分布的离散点图,计算出了各参数与深度的回归公式,研究表明,Hσ和hσ两个水平主应力与深度符合线性关系式,HK,hK,aK三个侧压系数与深度符合双曲关系式,HhK,Hμ,mμ三个比值参数与深度的双曲线关系不明显,总体上更接近于线性分布。对比研究表层、浅层的回归公式发现,两者的水平主应力回归公式差异显著,侧压系数回归公式差异较小,比值参数的回归公式基本一致,揭示基于工程的表层应力测量数据也可以用于脆性地壳的应力积累与地震活动性分析中。分析区域能量积累状况,提出对于mμ>0.7的浅部逆断点,需结合Hμ的值综合确定其能量积累程度;测点的Hμ,mμ值综合研究后认为渤海海峡19个表层测点及周边86%的浅层测点处于中低水平的应力积累中,地壳稳定性高;京津唐地区的部分测点应力积累水平较高,地壳稳定性差,需要密切关注,但对跨海通道工程的影响不大。取得的认识对环渤海区的构造应力场、断裂活动性研究及通道工程的建设具有重要的参考意义。

To identify the difference of current geostress distribution and stress accumulation in surface layer and shallow surface layer of Bohai strait and surrounding area,the data of 5 shallow hydraulic fracturing drills along the axis of the channel and the other deep drilling data in surround area were collected. The dispersed point chartsof stress varying with depth were established and the regression formulas of each parameter with depth were calculated. The research shows that σ,Hσ hchange with depth linearly and K,HK,hK achange with depth hyperbolically. K,Hhμ,Hμ m change with depth almost linearly. The comparison of the regression formulae of surface and shallow layer show that the difference of regression formula of horizontal principal stress is significant,the difference of regression formula of lateral pressure coefficient is small and the difference of regression formula of ratio parameters is basically the same. These indicate that the surface stress data can be applied to the analysis of stress accumulation and seismic activity in the brittle crust. The combination of μ m with μ H is necessary to determine the energy accumulation at the points of μ m0.7 in stress accumulation analysis. The comprehensive research on μ m and μ H lead to the conclusion that 19 surface points in Bohai strait and 86% shallow points in the surrounding district are in the middle-low level of stress accumulation,and the crustal stability is high. Some points in Beijing,Tianjing and Tangshan are in the state of high stress accumulation,and the crustal stability is low which need more attention. But these have little impact to the cross-sea corridor.