【作者】 唱伟；

【导师】 殷琨； 蒋荣庆；

【作者基本信息】 吉林大学 ， 地质工程， 2004， 博士

【摘要】 基坑工程主要包括基坑支护体系设计与施工和土方开挖，是一项综合性很强的系统工程。由于各地区的地质条件不同，因此基坑工程具有很强的区域性和很强的个性。其支护体系承受的土压力也具有较强的时空效应。基坑工程的区域性和个性的特点，为基坑围护设计的研究提供了较大的空间，研究相应的基坑稳定性，支护结构的内力及变形，周围地层的位移对周围建筑物和地下管线的影响及保护的计算分析，。以便采取经济实用的基坑支护方案，具有重要的理论意义和实际效益。本文对上述问题进行了研究，主要内容包括：（1）基坑支护方法的选择，结合目前常用的支护结构形式，分别论述了其结构特点和适用的范围，提出了多种支护结构型式综合应用的特点。（2）止水、降水体系及排水措施设计研究，提出了地下水对基坑支护稳定性的影响的观点。（3）结合北京某地区的地质情况和工程实际，提出了新的支护结构设计方案。主要包括方案的选择，土钉墙与桩锚结合支护结构的支护体系设计，基坑开挖及监控测量。其中重点对深基坑桩锚支护，土钉墙的设计计算应用有限元等方法进行了理论分析。（4）论述过程结合了工程实例和实际的设计数据。经过工程实践达到了基坑围护设计的目的和效果。 对上海宝钢地区二个典型的基坑稳定分析研究中，运用了多种施工方法，解决了软土地基无支挡边坡的稳定问题，PHC桩代替宝钢建设常用的钢管桩也大大地节省了投资，边坡的稳定也很好的保护了PHC桩。基坑支护超深地下连续墙的应用，说明该工艺仍然有很强的生命力，深度达50m的地下连续墙，又一次创造了全国之最。漩流沉淀池施工中承压水的问题也通过深井降水的合理设计得到了解决。基坑支护体系一般包括挡土体系和止水体系，支护结构一般承受土压力和水压力的作用。支护体系的选择受区域的影响较大，地下水位的高低对支护体系的选择也会造成很大的影响。多种支护结构型式的综合应用是解决特殊地区基坑工程结构支护的有效办法。 <WP=118>另外，通过对基坑支护体系的被动区土质的改良，降低地下水位等措施可以有效改善支护结构的受力状况，采用的办法主要有深层搅拌法，高压喷射注浆法及压力注浆法等。研究项目基坑分两种截然不同的支护方式，上部采用土钉墙围护，基坑下部为护坡桩结合两道锚杆支护的方案，基坑周围设置降水井，论文对单道锚杆和多道锚杆分别进行了计算。单道锚杆支护结构计算分别采用静力平衡法及等值梁法，根据试算法插入深度t值需先进行假定墙的插入深度确定后来计算支撑力，为了安全起见，可按插入深度增大前的主动与被动土压力合力计算支撑力即 RA=EA-EP式中：RA …………支撑力EA …………主动土压力合力EP …………被动土压力合力随之可求围护墙的弯矩分布，Mmax为剪力为零点的位置，等值梁法的计算略述。无论何种支护结构形式，关键的问题在于支撑点的设置深度、支撑和围护墙的刚度，围护墙插入深度及坑底土质的好坏，应用弹性地基梁法对单道锚杆的支护结构与工程界常用的等值梁法的计算结果从理论上作了比较，并有如下结论：（1）支撑点的设置深度对结构的安全影响较大，当支撑位置下移时，最大的水平位移会上移，同时桩身弯矩峰值明显减小，即支撑点下移至一定深度后对维护墙的受力有利，但对墙顶位移控制是无益的。（2）围护墙的插入深度影响方面，墙的插入深度增加墙体变形和弯弯矩值减小但变化不大，因此当插入深度已经满足土体强度与围护墙的稳定时，再加上深度对墙体变形和弯矩作用影响不大。（3）支撑刚度的影响，支撑刚度增大时，墙顶位移减小，直到增加到临界值后影响变小（4）围护墙刚度的影响，围护墙厚度增加，墙身变形就相应减小，围护墙弯矩也进一步增加，但是利用增大围护墙刚度来减小变形时应结合经济因素一同考虑。（5）坑底土m到值的影响，计算发现m值的偏差对墙体受力和变形的影响幅度不大。多道锚杆支护结构的等值梁法。如果将单道支撑的围护结构视为一次超静定结构，则多道 支撑就是多次超静定结构，因此在用等值梁法计算多道支撑的围护结构时，常常又引入新的假定条件。在软土地基上开挖9m以<WP=119>上的基坑时，常设两层或两以上的支撑。经分析发现，多层支护结构中关于支撑和墙体的刚度，墙体插入深度及m取值等因素的影响与单撑支护结构类似。本文采用极限平衡分析方法对土钉墙内部稳定性进行了分析，滑动面、破坏面的形状假定为双折线、圆弧线、抛物线或对数螺旋曲线进行了描述。利用重力式挡土墙稳定性分析法进行了外部稳定分析，通过了抗滑动稳定性验算，抗倾覆稳定性验算及墙底土承载力验算。根据以上分析验算，该地区的土钉墙和桩锚组合支护方式为：-7.0m以下采用桩锚结构，-7.0m以上采用土钉墙进行护坡。 参数：（1）护坡桩顶标高-7.0m （结合二道锚杆）桩径Φ800mm 桩长18.85m、 桩中心距1.6m。 (2) 锚杆：第一道锚杆标高-7.2m、斜度15°、杆长25m、杆径150mm。第二道锚杆标高-13.2m、斜度15°、杆长25.0m ，(3) 梁：横面尺寸1000mmX500mm、标高-7.0m (4) 土钉墙：与计算的数据相对应。本文采用《北京理正基坑支护设计软件》对设计的数据进行了?更多还原

【Abstract】 Excavation engineering mainly include excavation support system design and construction, and soil excavation etc. It is strong comprehensive system engineering. Because geological conditions of every area are different, excavation engineering has a very strong regional and individual characters. The soil pressure that support systems bear has stronger space-time effect too. It is excavation engineering regional and individual characters that offer us bigger space to research the design knowledge of excavation support, study corresponding excavation stability, and internal force and displacement of the support structure, the impact on the building around and underground pipeline of displacement of the stratum, and computational analysis of protection. By that means, we can adopt the economic and practical excavation support project. So it has the important theoretical and reality meanings.This text has carried on research to above-mentioned problems, the main content includes: (1) the choice of excavation support method. Combine the commonly used support structure form at present, the author put forward the characteristic composite using many support <WP=121>structure forms; (2) the study on water seal ,precipitation and drainage measures. Put forward the influence on support engineering stability by precipitation system. (3)Combine project reality, this paper put forward new design project of the support structure. Include choice of scheme, support system design of soil-nailing wall and anchor-pile composite supporting structure, excavate and monitor measurement in excavation engineering. It discusses especially the finite element method on anchor- pile support in deep excavation and on design computing of soil-nail wall. (4) This paper demonstrates the issue with the case study and real design data, and achieves the design purpose through practice.We research the stability of two typical foundation ditch in the region of Shang HAI Bao Gang,using sorts of construction,and resolve the stability problem of un-sustain side slope in soft soil foundation,reducing largely investment outlay by PHC pile instead of steel-pipe pile which is always used by construction of Bao Gang,the stability of side slope protects PHC pile.The application of super-deepth constinous concrete wall in foundation ditch sustain instructs that it still holds intensive vitality,the deapth of 50 m of constinous concrete wall creates the maximum of national. The problem of confined water in the construction of cyclone desilter is soluted by proper designing of depth well precipitation.Excavation support systems generally include soil retaining system and drainage system; it generally bears soil pressure and water pressure. So its choices are greatly affected by area, and the levels of underground water have greatly influent on support system choice, for example. The composite application of many support methods is the effective way to research the problems of excavation supporting structure engineering in some special regions. In addition, through the means such as improving the soil in supporting structure passive district, reducing the underground water level etc, we can improve the strength state of structure effectively. <WP=122>The method adopted include mainly intermix in deep layer, high pressure spray casting and pressure casting etc. The researched excavation has two completely different structures. The top of it adopt soil-nail wall and the bottom adopt slope protection pile combined with two bolting. There drill precipitation wells around the excavation. This text calculates the single anchor stock and many anchor stocks respectively. The calculation of single anchor support structure adopts static balance method and equivalence beam method respectively. According to trial method, depth of penetration t needs to be supposed in advance, and then calculate support strength. On the safe side, we should use active soil pressure and passive soil pressure to calculate the support strength before T increased. That is RA=EA更多还原