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在水文地质和工程地质条件不良地区或周围有相邻建筑物,基坑无法放坡开挖,而打桩或设置井点会使邻近建筑物地基受到震动或产生有害的附加沉降,引起建筑物开裂,甚至发生危险的情况下修建工程,采用地下连续墙可获得很好的效果。地下连续墙具有多种功能,多种用途,它既可用来截水防渗,也能用来挡土承重;既可用作临时性措施,又可用作永久性结构。浇筑地下连续墙可在十分狭窄的场地施工,不必设置模板和支撑。地下连续墙可作为新建地下工程结构物的边墙,修筑在既有建筑物十分邻近的地方。作为永久性结构,地下连续墙显然要承受较大的荷载,因此,必须考虑稳定性方面的要求,要使地下连续墙插入基坑底面以下足够的深度或插入坚硬岩层,有时尚需设置圈梁或锚杆。这项新技术可使我们修建更大更深的地下构筑物。通过多年来的工程实践,地下连续墙施工工艺有了不少的改进和提高。这里介绍的多头钻成槽机,不仅速度快,精度高,而且成槽壁面平整,是一种较好的成槽工具。目前地下连续墙对于岩溶地区,含承压水水头很高的砂砾层还不能采用。如果设计管理不善,泥浆可能会造成现场潮湿泥泞,影响施工环境。土层条件特殊,有可能出现超挖。在城市地区开挖,尚须注意相邻建筑物、地下设施和土的物理力学性质、地下水位高度、施工过程中和竣工后的浮托力等,才能取得预期的效果。
Adjacent buildings in and around areas with poor hydrogeological and engineering geology conditions, pits cannot be gradu- ally excavated, and the foundations of adjacent buildings are subject to vibration or harmful additional settlements, causing cracking of buildings. Even in the case of dangerous construction projects, the use of underground diaphragm walls can achieve good results. The underground continuous wall has many functions and many uses. It can be used to cut off water seepage and can also be used to hold earth weight; it can be used as a temporary measure and can also be used as a permanent structure. The construction of a continuous diaphragm wall can be done in a very narrow site without the need for formwork and bracing. The underground continuous wall can be used as the side wall of the newly-built underground engineering structure, and it is built in the vicinity of the existing building. As a permanent structure, the underground continuous wall obviously bears a large load. Therefore, the stability requirements must be considered. To make the underground continuous wall insert deep enough below the bottom of the foundation pit or to insert into a hard rock, there is a need to set ring beams for fashion. Or bolts. This new technology allows us to build larger and deeper underground structures. Through many years of engineering practice, there have been many improvements and improvements in the construction of underground continuous walls. The multi-drilling slotting machine introduced here is not only fast and accurate, but also has a smooth groove wall surface. It is a better slotting tool. At present, underground continuous walls cannot be used for karst areas where gravel layers containing high pressure and water heads are used. If the design is poorly managed, the mud may cause wet mud and mud on the site and affect the construction environment. The soil conditions are special and there may be over-excavation. Excavation in urban areas must pay attention to the physical and mechanical properties of adjacent buildings, underground facilities and soils, the height of groundwater level, and the floatation force during and after construction in order to achieve the desired results.