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青岛理工大学毕业设计（论文） 第86页 外文文献翻译 Common causes of the collapse pit Foundation construction is an important component of building construction, to improve basic construction of security is very important. According to the Ministry of Construction accident statistics in recent years, in the basic construction, excavation foundation trench, hand-dug pile collapse caused by construction accounted for 65% of total collapse, indicating that the base foundation for ensuring the safety of tank building foundation construction security. At present, Chengdu area construction Building construction for infrastructure, the commonly used form of excavation, foundation collapse accidents have occurred, causing a certain amount of economic losses and casualties, therefore, analyze causes of accidents and preventive measures that can help us reduce the possibility of collapse Foundation, to improve basic construction of security. Common cause of the collapse pit 1. Kengbi choose the form of unreasonable Foundation construction, Kengbi form mainly two: First, by slope ratio method, ie, natural grading; second supporting structure is used. Practice has proved that the form of a direct impact on excavation pit Kengbi security, if used improperly buried for the construction of a hidden pit. Construction unit during construction organization design, much thought to save investment and shorten the construction period, the correct form of neglect Kengbi selection, which appears Kengbi form of improper selection. In most projects, the slope ratio method used by support structure than the savings investment, and therefore the construction units in this way is often the preferred form of construction as a foundation. But the slope rate method can only be used when the project conditions permit, if the construction site can not meet the specifications required by the limited slope ratio or rich groundwater, soil stability is poor, generally can not consider the slope ratio method, otherwise prone to problems, resulting Kengbi collapse. When the slope ratio method does not have the conditions used, the foundation should support measures adopted. Chengdu common supporting structure are: soil nailing wall, spray anchor, such as the pouring of concrete support. Prior to the construction project which should be based on the surrounding environment, geological and hydrological conditions, and requirements for construction of support in the form of a reasonable selection, design, if determined to save money support in the form of thumb, it may not meet the purpose of supporting , the same situation prone to Kengbi collapse, causing accidents. As May 2001, the city occurred in a construction site collapsed gunite Wall, the collapse of long range 13m, width 2.5m, high-6m, causing close to the construction site of a building cars channel interrupt edge of a pit underground water pipes φ200mm leaks, broken drains, Pit houses, fences and roads cracked serious. The reason is because it has a foundation with a basement car are only separated by a channel, the use of shotcrete wall protection, restrictions on the length of the bolt, so this Kengbi, better results with concrete piles, security is higher. 2. Kengbi irregular earthwork construction Some construction units in the foundation pit, do not attach importance to the construction management and control, free to change the construction design, in violation of technical specifications, but also brings risks foundation construction, the main cause Kengbi collapse. 青岛理工大学毕业设计（论文） 第87页 Main features: First, when the slope by slope ratio method rate of less value. When the project conditions permit, the pit slope rate of commonly used construction method. But the slope ratio method used must be in strict accordance with technical requirements, improve control of foundation pit construction rate of the slope. However, in practice, often because of earth excavation construction unit slope when rate control is not good or geological survey information is not accurate, resulting in greater than the expected depth of excavation depth, there is less than pit slope design value Kengbi situation the foundation Kengbi in an unstable state, the most vulnerable Kengbi collapse. Excavation of a site such as the construction of the city, according to geological survey report on design for the excavation depth 2.7m, excavation of soil conditions found does not match with the geological survey report on the need overbreak 2.1m, due to limited space, can not meet the design cut slope coefficient , resulting in pit Kengbi slope is less than the design value, the construction process Kengbi collapses, the support measures taken against Kengbi before continuing construction. Second, construction of retaining structure for excavation did not seek. Conducting soil nailing wall anchor structure or construction of spray, in accordance with regulatory requirements, should be based on soil nail or bolt row spacing layer excavation, a layer of earth immediately after excavation support, support structure to be meet the design requirements and then the next layer of earth excavation. However, the construction site, often a result of excavation work closely with the Wall does not match the construction, earth excavation operation too fast, so that a large area for a long time Kengbi standing bare earth, created the conditions for the Kengbi collapsed. August 2004, the city site during a soil nailing wall construction, nearly one-time excavation depth 5m, failed to carry out soil nailing wall, moving a large area of collapse, resulting in a layer of brick and wood houses Kengbian the basis of nudity, sink, wall cracks, this section had to be dismantled brick wall, with gravity retaining walls within the foundation as a supporting structure, backfilling earthwork, masonry walls and re-formation of compaction. 3. To the neglect of surface water treatment Foundation construction of the "flood" One of groundwater, the second is surface water. Because groundwater is not properly handled will directly affect the basis of foundation engineering construction and pose a threat to the stability of pit Kengbi, so all parties involved construction of underground water is taken very seriously, from the investigation, design and other aspects of capital investment can be guarantee. Now widely used in Chengdu Tube Well, good effect of precipitation, groundwater effectively eliminate the adverse effects of excavation Kengbi. The construction of surface water because no significant effect on the basic but often overlooked, in fact, the stability of surface water on the role of foundation Kengbi also a significant influence. Surface water can be divided into "one out of a dark" In both cases, "that" mainly refers to the construction site that may occur within the ground surface water, such as rain water, construction water, groundwater pumped from wells and other precipitation; "dark" is mainly refers to the pit below the surface of the pipe network around the leakage, burst pipes and other surface water produced. Without the timely processing of these two cases will pose a threat to the stability of Kengbi, may cause Kengbi collapse, especially in underground pipe network generated surface water, its difficult to be found, the consequences are often more serious. The end of August 2004, heavy rains in Chengdu, a Wall site soil nail wall collapse suddenly, the reasons for post hoc analysis found that the collapse of parts of a disused water channel, high rainfall, the other can not be timely rain water drainage ditch, the ditch water intrusion , directly into the Wall inside the