摘要
中国东部现今构造应力场的特征表现为以水平应力为主,最大主压应力方向为近EW向,而秦巴地区已有地应力测量资料显示地应力最大主压应力方向以近SN向为主。为了查明其原因,结合三峡引水工程秦巴段地壳稳定性调查评价工作,在东秦岭东江口花岗岩体内布置一口地应力综合测量孔,进行水压致裂法与AE法地应力测量对比研究。在东江口花岗岩体600m深钻中,将埋深30～596m分27段进行水压致裂法地应力测量,获得20组水平主应力有效数据和25个裂缝破裂方向数据;同时,将埋深为75～599m分11段进行AE法现今最大主应力值测量,获得11个有效数据。将上述2种方法在同一测量深度的测量结果对比后发现:在200m深度以上,2种方法所得结果相近;在200m深度以下,水压致裂法测量的最大水平主应力值比AE法测量的最大主应力值大10MPa左右,前者与邻区已有的水压致裂测量数据相比,普遍偏高,而后者与邻区同一深度的测量结果相近。造成上述结果的原因是,在200m以下岩体中存在残余古构造应力,它与现今构造应力等叠加在一起构成地应力。综合研究结果表明:残余古构造应力是秦巴地区地应力的重要组成部分,不容忽视,上述研究结果对于充分认识秦岭中新生代造山带地应力场的分布规律具有重要的理论意义;同时,还可为穿越秦岭和大巴山的生命线工程的深埋长隧道的规划和设计提供依据。
The result of earthquake mechanism solutions shows that the maximum principal stress axes of the modern tectonic stress field are close upon horizontal and the direction of the maximum principal stress is close to EW in east China;but the result of geostress measurements show that the direction of the maximum horizontal principal stress is close to NS in the Qinling—Bashan Mountain.In order to find the reason,the geostress measurements by AE method and by hydraulic fracturing technique were carried out in the same borehole.The borehole with depth of 600 m was drilled in granite rock mass at Dongjianhkou,Shaanxi Province.From 30 to 596 m,20 valid data of horizontal principal stresses and 25 data of the directions of the fissure by the hydraulic fracturing technique are achieved;from 75 to 599 m,11 data of the maximum principal stresses by AE method are gained.Above 200 m,the data of the hydraulic fracturing technique is consistent with that of AE method at different points in the same depth;but below 200 m,the maximum horizontal stress by the hydraulic fracturing technique is 10 MPa larger than those by AE method.At the same time,the data are larger than those by the hydraulic fracturing technique in its neighbouring region.On the contrary,the data by AE method are consistent with it.The result is that the paleotectonic residual stress exists in granite rock mass below 200 m,and the geostress field is composed of the modern tectonic stress field and the paleotectonic residual stress field.The data by AE method are modern tectonic stress,but the data by the hydraulic fracturing technique are the geostress.The result shows that the paleotectonic residual stress is an important composition of the geostress in the Qinling—Bashan Mountain which is the Mesozoic-Cenozoic orogenic belt.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2007年第1期81-86,共6页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(40472153)
地质调查局地质调查项目(1212010340301)
关键词
岩石力学
水压致裂法
声发射法
残余古构造应力
地应力
rock mechanics
hydraulic fracturing technique
AE method
paleotectonic residual stress
geostress
