写一篇关于地铁防水结构自防水，外包防水组成内容和失效原因的论文

摘要：地铁防水结构是采用自防水和外包防水组成的。自防水结构包括基层、保护层、表层，而外包防水结构则主要由底板、侧壁、立壁及其他部位的外包材料组成。本文详细介绍了地铁自防水及外包防水的原理以及它们之间的关系；同时也列出了常见的地下工程失效原因，如不正常浸泡、不正常平整度、不正常施工方法、开裂及耐久性能低下。最后，本文进一步思考了如何避免这些原因对地下工程造成损害，并提出了相应的对策。 关键词：地下工程; 自然保护; 外包材料; 失效原因; 对策 1. Introduction Underground engineering is an important part of urban construction. In order to ensure the safety and stability of underground engineering, it is necessary to have a good waterproof structure. The waterproof structure of underground engineering mainly includes self-waterproof structure and external waterproof structure. The self-waterproof structure includes base layer, protective layer and surface layer, while the external waterproof structure mainly consists of bottom plate, side wall, vertical wall and other parts of external materials. This paper will discuss the principle of self-waterproofing and external waterproofing in detail, as well as their relationship between each other. It will also list common causes of failure in underground engineering such as abnormal immersion, abnormal flatness, improper construction methods, cracking and low durability performance. Finally, this paper further considers how to avoid these causes damaging underground engineering projects and puts forward corresponding countermeasures. 2. Self-Waterproof Structure The self-waterproof structure is composed of three layers: base layer (base material), protective layer (protective material)and surface layer (surface material). Generally speaking, the base material is used for load bearing function which can bear the pressure from above soil or other structures on ground level; while the protective material can protect against water seepage by blocking water flow through its pores or cracks; finally the surface material is used for decoration purpose which can make sure that there are no gaps between different parts or components on ground level so that no water can penetrate into them from outside environment . 3. External Waterproof Structure The external waterproof structure mainly consists of bottom plate , side wall , vertical wall , etc., which are made up by different kinds of materials such as asphalt felt , PVC sheet , bitumen membrane , etc.. These materials have good performance in terms anti-seepage ability due to their impermeable nature . Besides that , they also possess good elasticity so that they are able to adjust themselves according to changes in temperature or humidity . This makes them suitable for use in outdoor applications where temperature fluctuation may be frequent . 4. Causes Of Failure In Underground Engineering Projects There are many possible causes leading to failure in underground engineering projects such as: abnormal immersion caused by poor drainage system ; abnormal flatness caused by uneven compaction ; improper construction methods leading to incomplete compaction ; cracking due to lack of flexibility ; low durability performance resulting from aging process over time . All these factors could lead to water leakage which may cause serious damage if not addressed timely . 5. Countermeasures To Avoid Damage Caused By Failure In Underground Engineering Projects In order to avoid damage caused by failure in underground engineering projects , some countermeasures should be taken including : improving drainage system around project site ; ensuring even compaction during construction ; using flexible materials with better elasticity ; inspecting regularly for signs of aging process over time . All these measures should be taken into consideration when constructing an underground project so as to ensure its safety and stability over time .