山脊急拐弯处地下局部含泥带揭露及成因解释——以广东CSNS场地为例  

DISCOVERY AND EXPLANATION OF ONE MUDDY GIRDLE UNDER SHARP TURN OF ONE RIDGE——A CASE STUDY AT THE CSNS SITE OF GUANGDONG PROVINCE

作　　者：尚彦军[1,2] 魏思宇[1] 金维浚[1] 林达明[3] 杨朋[1] SHANG Yanjun;WEI Siyu;JIN Weijun;LIN Darning;YANG Peng(Key Laboratory of Shale Gas and Geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029;Xinjiang Institute of Engineering,Urumqi 830023;Researeh Institute of Highway,Ministry of Transport,Beijing 100088)

机构地区：[1]中国科学院地质与地球物理研究所中国科学院页岩气与地质工程重点实验室,北京100029 [2]新疆工程学院,乌鲁木齐830023 [3]交通运输部公路科学研究院,北京100088

出　　处：《工程地质学报》2018年第3期561-571,共11页Journal of Engineering Geology

基　　金：国家自然科学基金(41372324);新疆科技厅国际合作项目(20166017)资助

摘　　要：在广东南部低山丘陵区剥蚀卸荷作用或许会导致地下一定深度地应力弱化和局部破碎泥化带生成,这一猜想在中国散裂中子源(CSNS)场地工程地质勘察中得到了证实。电法物探剖面显示出地形上山脊由330°急转为220°向急拐弯处地下局部低阻区、4个钻孔中揭露了完整变粒岩中蚀变长英质变质石英砂岩部位30~40 m深度范围出现局部泥化带。后续施工开挖中也揭露出此现象。数值模拟表明,受剥蚀卸荷影响的山脊近直角拐弯处一定深度范围内应力降低,靠近岩脉与变粒岩接触带岩体质量局部变差,出现破碎带,并控制了地下水局部富集和邻近低洼沟谷中泉水的生成。本研究揭示了山脊突变对地应力和岩体结构的影响,可望为类似条件下地质异常分析提供一定借鉴。Stress-release zone always connects with alpine valleys or a certain scale of underground engineering,which is generally thought to be caused by stream trenching or large scale engineering excavation. However there are few research in stress-release under the ridge＇s sharp turn. During the engineering geological investigation in the CSNS site which located in southern Guangdong Province,leakage occurred in drilling process of four adjacent boreholes and found locally broken argillization zone in the intact rock. To study and explain this phenomenon,we first arranged some geophysical lines across the engineering site to probe the underground. And the electrical geophysical profile indicates there is a local low resistivity zone exists under the ridge sharp turn. Then,during thegeologic mapping work,we found that the argillization zone just located in the contacting zone between northern granite belt and southern granulite belt. Third,by analysis the engineering geological investigation report,we circled the muddy zone in borehole profiles and contour maps,which tallies with geophysical results. After all these outdoor and indoor works,we used computer building an authentic surface model to simulate the influence of weathering and unloading on the mountain from earliest times. The numerical results show that stress unloading happened in a certain depth under the ridge＇s sharp turn because of the erosion unloading. It also made partial rock quality worse which approached to the contacting zone of dike and granulite,and formed crushing zone and control the local enrichment of groundwater and the generate of fountain. We analyzed the geological prospecting and geophysical data to conjecture what caused muddy zone in borehole ZK94 and neighboring areas＇ low RQD,and verified it by numerical simulation. We found that the muddy zone was caused by multiple factors. First and the most important factor,the metamorphic sandstone developed in the contacting zone of granite and granulite was harder and brittler than the o

关 键 词：花岗岩 变粒岩 片麻岩 泥化碎裂岩 剥蚀卸荷 地下水 

分 类 号：P642.3[天文地球—工程地质学]