基于微动HVSR法的基岩面探测研究--以深圳16号线共建管廊项目为例

Study on bedrock surface detection based on microtremor HVSR method: take Shenzhen Line 16 co-construction pipe gallery project as an example

盾构掘进穿越上软下硬地层属于高风险工程,在盾构施工前需根据基岩面特征优化掘进参数的设置,管控施工风险,保障经济效益.灰岩地区易受溶蚀作用影响,部分区域形成溶洞,部分区域发育溶沟溶槽,导致基岩面的深度变化大,对盾构施工造成重大影响,我们亟待寻找一种能快速准确识别岩溶区基岩面的解决方案.微动HVSR法是一种简单有效的被动源地震勘探方法,已被广泛应用于场地类型评价、地震放大效应评估等方面.本文以深圳16号线共建管廊项目为依托,将HVSR法用于快速地层分界面识别,通过对比分析不同的HVSR法界面深度估计经验公式,总结出一套快速准确识别基岩面的方法,经实际钻孔验证,达到了95%的识别准确率.微动HVSR法可以快速准确地识别基岩面,满足城市地下空间精细探测的需求,具有绿色环保、经济、施工便捷等优点,值得推广应用.

In shield tunneling construction, passing through the upper soft and lower hard strata is highly risky, so it’s necessary to optimize the setting of tunneling parameters according to the detailed characteristics of the bedrock surface before construction. Achieving the purpose of controlling construction risks and ensuring economic benefits. Under the influence of dissolution, limestone areas will easily form karst caves. The karst caves have a vertical height ranging from a few meters to a dozen meters. Furthermore, limestone areas will develop into karst ditches and troughs, which have an extension length up to hundreds of meters. These reasons will lead to abrupt changes in the bedrock elevation. The variation of bedrock elevation has a significant impact on shield construction. There is an urgent need to find a solution that can quickly and accurately identify the bedrock surface in karst areas. The Microtremor HVSR survey is a simple and effective passive source seismic method which was widely used in seismic site classification and amplification factor investigation. This paper uses the Microtremor HVSR method to identify the bedrock-soil interface based on the Shenzhen Line 16 co-construction pipe gallery project. This project is located in Long gang District, Shenzhen, Guangdong Province. The stratigraphy in the area is mainly limestone which was subjected to strong dissolution. By comparing and analyzing different empirical equations for estimating the bedrock-soil interface depth, we concluded a quick and accurate method of identifying the bedrock-soil interface. The output of the proposed method is verified by geological drilling with 95% accuracy. The Microtremor HVSR method can quickly and accurately identify the bedrock surface. The accuracy of the Microtremor HVSR method meets the needs of urban underground space detection which has high precision detection requirements. This method also has the advantages of green environmental protection, economic, convenient construction, etc. It is worthy of popularization and application.