向家坝水电站大坝坝基防渗墙施工技术难点及对策

Technological Difficulties and Countermeasures on Construction of Diaphragm Wall on Foundation of Xiangjiaba Hydropower Dam

向家坝混凝土大坝坝基分布有规模较大的IV、V类岩体,强度较低,遇水泥化,不满足坝基抗渗抗压的要求,设计采取防渗墙置换方式处理。根据向家坝坝基防渗墙在廊道内施工的特点,利用泥浆净化器解决成槽的弃浆清理问题,利用廊道顶设置起吊设备解决设备材料转运问题,在坝前布置临时通道输送混凝土确保浇筑的连续性,同时根据挠曲破碎带的地质特性,采取增设降水管井、高喷灌浆等措施解决挠曲破碎带的塌孔和孔底沉渣问题。质量检验表明防渗墙深度满足设计要求。

The large scale rock mass of IV and V types distributing on the foundation of Xiangjiaba concrete dam fails to meet the requirements on anti-permeability and anti-pressure of the dam foundation due to its low intensity and argillization in water,therefore diaphragm wall substitute mode is designed to solve the problem.The construction of diaphragm wall on foundation of Xiangjiaba dam features being in the gallery,accordingly,the grooving discarded mud is schemed to be cleared up by mud purifier,while the transportation of equipments and materials are designed to be conducted through installing lifting appliance on the roof of gallery,with temporary access road arranged in front of the dam for concrete transporting on purpose of guaranteeing continuous pouring.Furthermore,the problems of sinking hole and sediment at hole bottom of the bending shuttered zone are solved through constructing precipitation tube well and high sprinkling irrigation grouting upon the geological characteristic of the bending shuttered zone.Inspection results show that the construction quality thereof meets the design requirements.