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西甘池隧洞位于南水北调中线(北京段)惠南庄泵站—大宁调压池输水干线范围内,是南水北调工程北京段最长的输水隧洞。隧洞支护采用锚喷联合支护,具体参数:锚杆为2.0~2.5 m长的Φ20 mm水泥砂浆锚杆,Φ8 mm钢筋网间距150×150 mm~200×200 mm,喷射混凝土厚度在10~20cm。根据实际揭露的围岩情况来看,地质条件复杂多变,围岩软硬相间。在软弱破碎洞段,如节理裂隙密集分布、夹泥严重,滑石片岩与大理岩互层,滑石片岩强风化以及溶蚀段等,由于围岩自稳时间短、变形较大,极易发生坍塌,必须加强支护,为确保安全,经现场确定,先进行钢支撑支护后,再进行喷锚支护,地质异常破碎带加钢管进行超前支护。钢支撑能在较短的时间内使工作面趋于稳定,同时抑制围岩较大变形;且在喷锚支护完成后,钢支撑与喷锚支护一起联合受力,大大增加了支护抗力,确保了开挖工程和施工人员安全。重点论述了不良地质段洞挖地质分析及支护技术措施、施工要点。
Xigangchi Tunnel is located in the midline of South-to-North Water Diversion Project (Beijing section) within Huinanzhuang Pumping Station - Daning Regulating Tanks Main Line, and is the longest water transfer tunnel in Beijing section of South-North Water Diversion Project. The support of the tunnel is supported by anchor and shotcrete. The parameters are as follows: the bolt is Φ20 mm cement mortar bolt with length of 2.0 ~ 2.5 m, the spacing of Φ8 mm steel mesh is 150 × 150 mm ~ 200 × 200 mm, the thickness of shotcrete is 10 ~ 20cm. According to the actual situation of the surrounding rocks, the geological conditions are complex and changeable, and the surrounding rock is soft and hard. Due to the dense deformation of joints and fractures, serious mud entrapment, interbedded layers of talc schists and marble, intense weathering of talc schists and dissolution sections, the surrounding rock is prone to collapse because of its short stabilization time and large deformation. Must be strengthened support, in order to ensure safety, confirmed by the site, the first steel support and support, and then spray anchor support, abnormal geological anomalies with steel pipe for advanced support. The steel support can stabilize the work surface in a relatively short period of time while suppressing the large deformation of the surrounding rock. After the support of the shotcrete and anchor is completed, the steel support and the shotcrete and anchor support are jointly stressed together, which greatly increases the support Resistance, to ensure the safety of excavation and construction workers. This paper mainly discusses the geological analysis of tunneling in poor geology and the technical support measures and key construction points.