Study on distribution characteristics and influencing factors of in-situ stress field in Gonjo region of eastern Tibet
Gonjo region of eastern Tibet which is located in the northern section of Jinshajiang fault zone has undergone complex geological tectonic evolution.The distribution and influencing factors of in-situ stress field are discussed through the characteristic parameters analysis of the main stress value and orientation,lateral pressure coefficients,tectonic stress value based on the measured data of in-situ geostress using hydraulic fracturing method.The results show that the measured main stress increases with depth.The stress are scattered at the depth less than 500 m but manifested as Sv＞SH＞Sh in linear at the depth more than 500 m.The gradient of horizontal main stress versus depth is lower than that of the regional background blocks.The regional dominant orientation of maximum horizontal principal stress is NNE,which shows a counterclockwise deflection comparing with the dominant NE-NEE regional tectonic stress direction derived from other tectonic stress indicators.Based on the analysis of lateral pressure coefficients,horizontal stress ratio,ratio of maximum shear stress and average horizontal stress(μm)and Sheorey model,it is indicates that the horizontal tectonic stress accumulation is in the low level and the Zigasi—Deqin fault is stable in this region.The influencing factors of the in-situ stress field mainly include gravity,topography and tectonic action.The influence of gravity action on geostress follows the law of hydrostatic pressure.Under the influence of topography the horizontal geostress is discrete in superficial crust(＜500 m)and the lateral pressure coefficient decreases from bottom to the top of slope in deep-cutting gorge.The tectonic action mainly concentrates on the range of Zigasi—Deqin fault on both sides,where the values and directions of the main stress are abnormal in local area.It is expected to provide theoretical basis for regional stability evaluation,site selection and construction of underground engineering.
NETL
NSTL
万方数据
