Excavation method of building foundation pit adjacent to existing tunnel under soil and rock geological conditions

Abstract

The invention provides a construction method for excavating a building foundation pit adjacent to an existing tunnel under the soil-rock geological condition. A gradual layered excavating construction method is adopted. The method specifically includes the steps of gradual layered excavation, blocky shallow excavation, small-interval rapid supporting and frequent measurement and timely feedback. According to the gradual layered excavation, layered excavation is conducted from the side, away from the tunnel, of the foundation pit to the side, close to the tunnel, of the foundation pit. According to the blocky shallow excavation, the blocky excavation mode is adopted for the foundation pit with the area being larger than or equal to 1000 m<2>, the length of each block is not larger than 20 m, and the width of each block is not larger than 20 m; in shallow excavation, the excavation depth of each layer is not larger than 3.0 m, and the volume of each block in blocky excavation is smaller than or equal to 1200 m<3>. According to the small-interval rapid supporting, the exposure interval of rock-soil bodies after excavation is short, and temporary supporting is quickly conducted immediately after excavation of each block of each soil layer. According to the frequent measurement and timely feedback, the displacement and stress changing conditions of the rock-soil bodies are monitored in real time during the construction period, and monitoring information is fed back in time. A remarkable effect of controlling deformation of the adjacent tunnel is achieved through the gradual layered type layered and blocky excavation.

Description

technical field [0001] The invention belongs to the field of civil engineering, and in particular relates to a construction method for excavating a building foundation pit adjacent to an existing tunnel under soil and rock geological conditions. Background technique [0002] At present, 10 cities in my country, including Beijing, Tianjin, Shanghai, Guangzhou, Wuhan, Changchun, Dalian, Shenzhen, Chongqing, and Nanjing, have urban subway rail transit, Hangzhou, Shenyang, Chengdu, Harbin, Xi'an, Xiamen, Suzhou, Qingdao, Dongguan, 33 cities including Ningbo, Foshan, Shijiazhuang, Zhengzhou, Changsha and Lanzhou are under construction, preparation or planning. With the continuous development of underground space and the vigorous construction of subway tunnels, more and more building foundation pit projects are inevitably adjacent to or intersecting with existing tunnels. The excavation of building foundation pits causes different degrees of soil stress release around the pit. As ...

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Problems solved by technology

With the continuous development of underground space and the vigorous construction of subway tunnels, more and more building foundation pit projects are inevitably adjacent to or intersecting with existing tunnels. The excavation of building foundation pits causes different degrees of soil stress release around the pit. As a result, the displacement of the supporting structure system and the stratum around the pit will cause additional stress and additional deformation in the adjacent tunnel. Excessive deformation will lead to the danger of tunnel cracking and leakage, which will affect the structural safety and normal operation of the tunnel. Therefore, it is necessary to study the building foundation. In order to provide a certain theoretical basis and useful reference for the future development, design and construction of underground space

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