桩锚支护体系在基坑中的应用与数值模拟分析

发布时间：2018-02-13 06:10

本文关键词： 基坑桩锚支护数值模拟监测　出处：《东华理工大学》2014年硕士论文　论文类型：学位论文

【摘要】：近几年,随着我国经济的快速发展,城市化水平的不断提高,城市土地资源紧缺日趋凸显。房地产、市政工程以及隧道工程的迅速崛起,加之城市地上空间使用范围的限制,使得更多的工程向着地下空间发展,便出现了地下商场、地下停车场、地铁站台、地下隧道等一系列的地下工程的兴建,基坑数目日趋增加,涉及领域不断扩大,基坑复杂性和难度也随之加大。基坑工程是建设工程中数量多、投入大、困难多、高风险的关键性工程项目。在基坑中,设计与施工既要确保支护系统在施工过程当中的安全,还要控制结构及其周围土体的变形,以保证周围环境的安全。桩锚支护结构是在20世纪80年代开始应用并快速发展起来的,现已经成为一种比较成熟,也是我们目前常用的基坑支护形式。随着基坑开挖深度加深、开挖环境日益复杂以及基坑坍塌事故的频发,这样不仅仅影响了工程工期同时也会增加施工的成本代价,因此为了使基坑在建(构)筑物达到安全有效的目的,挽回不必要的经济损失以及可能到来的不良的社会影响,需要对基坑工程进行实时监测。通过实际的监测数据来反馈基坑在实际的施工中的变化状态,确保基坑的安全。随着科学技术的发展,计算机现在已经应用到各个领域,数值分析和数值模拟在基坑工程也得到了广泛应用。利用数值模拟方法对支护结构进行分析,可以更好的归纳影响基坑开挖、支护的因素。本文结合具体工程实例-江西国光安福城市综合体基坑,对基坑进行桩锚支护体系设计、模拟分析和现场监测。结合工程概况、工程地质条件、周围的环境因素以及各个方案的工程造价,对比不同的支护方案,优选出最佳的支护方案为支护桩+锚索+高压旋喷桩联合的支护形式。利用FLAC3D软件,通过设定模型尺寸和边界条件,确定初始应力条件和选择本构模型,建立数值模拟分析的模型。通过对基坑开挖前后的最大不平衡力模拟得出,计算最终收敛。通过对桩身内力的模拟得到最大轴力、剪力、弯矩分别为2.649×105N、2.956×105N、9.058×105N.m,理论计算结果为2.62×105N、2.59×105N、8.78×105N.m,两者计算结果相差不大,基本一致。模拟锚索轴力得到的最大轴力值为3.851×105N,理论结算结果为3.6×105N,两者基本相等。通过对桩顶位移模拟得出桩顶的总沉降位移值为27.7mm,水平位移为35mm,两者都符合规范要求。通过模拟基坑在有支护和无支护条件下,每步开挖过程中的土体位移、内力,的对比可知,基坑在开挖较浅的情况下,土体的内力和位移变化基本一致。但是随着深度的增加,在无支护条件下,土体将会产生很大的内力、位移,造成基坑的滑塌,而在有支护时变化较小,说明桩锚支护体系保证了本基坑的安全。根据工程实际情况,制定了具体的监测方案,分别监测基坑四周的桩顶沉降位移、建筑物沉降位移、水位变化以及深层土体位移。通过监测可知,在基坑四侧的桩顶最大沉降量为10.39mm,最大沉降速度为0.65mm/d。建筑物最大沉降量为14.61mm,最大沉降速度为0.63 mm/d。基坑四周的水位基本维持在高程81~82m之间。最大深层土体位移为14.36mm。以上数据均在预警值范围之内,基坑处于安全状态。最后通过对桩顶沉降的监测位移值和模拟位移值进行比较得知,两者的变化基本一致,数值相差不大。
[Abstract]:In recent years, with the rapid development of China's economy, the continuous improvement of the level of city, city land resources shortage is becoming increasingly prominent. Real estate, municipal engineering and the rapid rise of tunnel engineering, and the city space restrictions on the use range, more and more engineering toward the development of underground space, appeared the underground shopping malls, underground parking lot, subway stations, underground engineering, a series of underground tunnel construction, the foundation pit number increasing, relates to the field of expanding excavation, complexity and difficulty increased. The foundation pit engineering construction project quantity, large investment, more difficult, the key project of high risk. In the foundation, design and the construction is to ensure the safety in the construction process of the supporting system, but also control the structure and deformation of surrounding soil, in order to ensure the safety of the surrounding environment. Pile anchor retaining structure in 1980s Start the application and rapid development, now has become a relatively mature, but also our common form of excavation. With the deepening of the depth of excavation, excavation and foundation pit environment increasingly complex frequent collapse accident, this not only affect the construction period and also will increase the construction cost, so in order to make the foundation pit in the building built (structure) is a safe and effective to save unnecessary economic losses and possible adverse social impact, the need for real-time monitoring of foundation pit engineering. Through the actual monitoring data feedback to change state of foundation pit in actual construction, ensure the safety of the foundation pit. With the development of science and technology, computer now it has been applied to various fields, the simulation has been widely used in foundation pit engineering numerical analysis and numerical. The supporting structure is divided by the method of numerical simulation Analysis can better induction effects of pit excavation, supporting factors. Combining with the specific engineering example - Jiangxi Guoguang Anfu city complex foundation, the design of supporting system of foundation pit anchor pile, simulation analysis and field monitoring. Combined with practical engineering, the engineering geological conditions, environmental factors around and each project cost, comparison different support schemes, the best supporting scheme for supporting pile + anchor + jet grouting pile retaining structure. Using FLAC3D software, by setting the model size and boundary conditions, to determine the initial stress conditions and the selection of constitutive model, numerical simulation model was established. Through the analysis of the maximum pit before and after the excavation of the unbalanced force is simulated, calculating the final convergence. The maximum axial force, through the simulation of the internal forces of the pile shear, bending moment are 2.649 * 105N, 2.956 * 105N, 9.058 * 105N.m, theoretical calculation The result is 2.62 * 105N, 2.59 * 105N, 8.78 * 105N.m, the two results are similar, basically the same. The simulated maximum axial force axial force of cable is 3.851 * 105N, the theoretical results is 3.6 * 105N, which is basically the same. The simulation results show the total pile top displacement value is 27.7mm to drop the pile top displacement, horizontal displacement is 35mm, both meet the standard requirements. Through the simulation of foundation pit in supporting and supporting conditions, internal force of soil displacement, each step in the process of excavation, the comparison shows that the shallow foundation pit in excavation case, internal force and displacement of soil with depth but basically the same. The increase in non support conditions, the soil will have a lot of internal forces, displacement, caused by the collapse of the foundation pit, and there is a little change in support, that the pile anchor support system ensures the safety of the foundation pit. According to the actual situation, formulate specific monitoring Solutions were monitored around the pit settlement of the pile top displacement, displacement and settlement of buildings, the change of water level and the displacement of deep soil. By monitoring the four side of the top of the pile foundation in the maximum settlement is 10.39mm, the maximum settlement rate of 0.65mm/d. building the maximum settlement is 14.61mm, the maximum settlement rate of 0.63 mm/d. water level maintained around the pit at the altitude of 81~82m. The maximum displacement of deep soil is more than 14.36mm. data are in the warning value within the scope of excavation in a safe state. The values were compared and simulated that the displacement monitoring displacement of pile top settlement, the change is basically the same numerical difference.

【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU753

【参考文献】