Study on the Geological Conditions of Deep Excavation Engineering for Metro Wind Shafts in Granite Areas
In order to study the engineering geological conditions of deep foundation pit in the zone affected by regional fault structure,with the general idea of"surface → line → point",the comprehensive investigation means of"five in one",including geological survey,ground geophysical exploration,in-hole geophysical exploration,motorized drilling and geotechnical testing,were adopted to find out the fault occurrence and width,formation distribution law and geotechnical physical properties within the scope of foundation pit.The investigation methods of deep foundation pit engineering suitable for complex geological conditions were summarized,which could provide reference for other similar projects.It was found from the geological survey that the foundation pit engineering was located in the fault affected zone of F2 region,and three groups of staggered joints were developed.The fault structure aggravated the development degree of joint cracks,resulting in severe rock fragmentation and differential weathering within the scope of the foundation pit.According to the transient electromagnetic method,the fault and the influence bandwidth of 55～65 m were obtained from the"line",and the spatial relationship between the foundation pit structure and the fault structure were initially established.According to the maneuverable drilling and the resistivity test in the hole,the distribution characteristics of"soft and hard"of the longitudinal rock mass in the foundation pit were revealed from the"point".The strata were severely affected by tectonic compression,the depth of fault was up to 60m,the weathering degree of rock mass was high,the strength was low,and the rock mass was mainly scattered,intermixed with fragments,and the space was irregular,showing the typical fault structural zone characteristics.By using the advantages of different exploration means,mutual verification and comprehensive analysis,the geological conditions and geo-mechanical characteristics of deep foundation pit engineering under complex geological conditions are found out,which provides a reliable geological basis for the design scheme.
metrodeep foundation pitcomprehensive investigationfault tectonic zonedifferential weatheringtransient electromagneticresistivity logging
NETL
NSTL
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