【作者】 林希强；

【导师】 汤凤林；

【作者基本信息】 中国地质大学 ， 地质工程， 2004， 博士

【摘要】 复合土钉支护技术是在土钉支护结构中复合了其它土体加固技术的岩土综合支护技术，是近几年来城市地区深基坑支护实践中发展起来的一种具有中国特色的土钉支护技术，可以针对不同的场地条件和地质条件，采取因地制宜、灵活多变的组合支护结构，克服了传统土钉支护技术的固有缺陷，具有广阔的应用前景。 复合土钉支护技术作为一种安全可靠、经济可行、快速简便的基坑支护技术，已在我国深基坑开挖支护施工中得到越来越广泛的应用。但目前对复合土钉支护技术的理论研究大大落后于工程实践，对复合土钉支护结构中土钉和复合加固部分的工作性能以及两者与土体的相互作用，对支护结构各部分的内力和变形的研究仍处于初步阶段；对复合土钉支护结构中复合加固部分的工作机理的研究，只有深层搅拌桩有人涉及，对于超前微型桩、预应力锚杆、冠梁、腰梁和面层的作用机理的研究目前还是空白；对复合土钉支护结构的大规模试验研究，还很少有人涉足，全面准确的试验或测试资料更为有限。 本文通过对基坑复合土钉支护结构进行较为全面的分析与测试，拟进一步揭示基坑复合土钉支护全过程的内力与变形特征，试图为复合土钉支护技术在国内更广泛地应用提供较为科学的依据。本文的研究工作内容为： (1) 讨论了复合土钉支护技术的形成、发展和研究现状，对复合土钉支护技术的优点、发展概况、应用前景和研究现状进行了综述，分析了复合土钉支护技术现有研究工作的不足。 (2) 根据复合土钉支护特点，在充分分析复合土钉支护结构各部分的工作机理的基础上，利用ANSYS有限元分析软件，建立了一个三维有限元分析模型。土的本构模型采用非线性德鲁克—普拉格(Drucker-Prager)模型；土体和搅拌桩采用20节点六面体等参单元；土钉、锚杆、冠梁、腰梁和加强筋采用具有尺寸特征的三维2节点梁单元；面层采用具有尺寸特征的三维3节点壳单元。土钉、锚杆、微型桩、冠梁、腰梁与土体的接触，采用双弹簧联结单元，模拟土钉、锚杆与土体之间的粘结滑移性能，模拟面层、微型桩、冠梁、腰梁和加强筋与土体的应力传递性能，以及模拟冠梁与微型桩顶的联结。根据复合土钉支护的施工特点，模拟基坑开挖与支护的施工过程。通过工程实例计算，较全面地给出基坑开挖支护全过程复合土钉支护结构各部分的内力与变形特征。 (3) 对广州市珠江新城E1-1地块项目基坑土钉支护工程和广州市天河商旅二区综合楼基坑工程进行现场测试工作。现场测试得到的测试数据稳定、丰富。通过对上述土钉支护工程现场测试结果的整理与分析，进一步揭示了基坑复合土钉支护结构开挖支护全过程的内力与变形特征，为确保工程的安全和质量提供监控信息，并为验证设计或分析结果的正确与合理性提供实测依据。有限元法作为一种强有力的数值计算方法，己经广泛应用于岩土工程问题的分析。有限元方法用于岩土工程问题存在一定的困难，主要在于土本构模型，包括模型参数的确定。但是，如果选择合适的模型，将有限元方法用来分析不同参数变化时土工结构工作性能的变化规律还是很有价值的。另一方面，如果通过试验或现场测试得到大量的受力和变形数据，检验有限元分析的可靠性，标定输入模型参数的取值范围，反过来又会促进有限元分析方法的发展。有限元法不仅能计算复合土钉支护结构中土体、土钉、面层，以及复合加固各部分的内力与变形，模拟基坑开挖支护施工过程等，而且可以考虑土体的非均匀性和各向异性的复杂性态。 复合土钉支护着眼于发挥原有土体的强度，并针对场地的土体具体情况，在基坑开挖前对其进行加固。预加固结构、土钉和其他加固支护结构与被支护的土体形成有机的整体。因此，在建立复合土钉支护有限元分析模型时，必须把支护结构与土体作为一个相互作用的体系进行分析。本文所建立的三维有限元模型，主要考虑具有有限元尺寸的土钉、微型桩、冠梁、腰梁、加强筋和预应力锚杆对半无限土层的三维作用，不考虑基坑的深度和平面形状的空间效应。为得到基坑稳定的最不利情况，分析得到最大变形，模型选用远离基坑角点的一段复合土钉支护边坡。由于土钉、预应力锚杆、微型桩、冠梁、腰梁和加强筋沿基坑水平方向和竖直方向以一定间距平行布置，每列竖向土钉的加固范围为通过两侧水平间距中点的竖向截面间的土体，厚度等于水平间距，沿基坑平面延长方向任取一段分析得到的结果都是一样的，也就是说，沿基坑平面延长方向可看作无限长，任意一段都是对称面，因此，可以取其中宽度等于土钉水平间距的一段进行分析。这块土体相对于通过土钉的竖直截面又是对称的，为了减少计算量，取其中的一半作为三维有限元计算模型，土钉的刚度也相应地取总刚度的二分之一。本文建立的有限元模型所采用的德鲁克一普拉格(Drucke卜Prager)弹性一完全塑性模型能够模拟基坑开挖过程中土的非线性和弹塑性特征;采用梁单元和接触单元模拟土钉和锚杆的拉、弯、剪作用及其与土体的粘结滑移性能，模拟超前微型桩、冠梁、腰梁及加强筋在复合土钉支护结构中相互作用和支护作用;采用壳单元和接触单元模拟面层及其与土体的相互作用;?更多还原

【Abstract】 The composite soil-nailing method is a geotechnical comprehensive shoring technique combining soil nailing with other soil reinforcement procedure. It is a soil-nailing technique with Chinese characteristics developed during the deep foundation pit sheathing practice in urban districts in recent years. The technique has overcome the inherence defect of traditional soil nailing, and found broad prospects of application. Based on site conditions and geological conditions, various composite soil nailing structures can be used.The composite soil-nailing method has found wider and wider application in deep excavation in China because of its advantages, such as: safe and reliable, easy to implement and less investment. However, theoretical research on the technique has fall behind its engineering practice recently. Research on behaviors of soil nail and the reinforcement parts; Research on interaction between soil nail and soil; Research on interaction between reinforcement parts and soil; Research on internal force and deformation of the supporting structure are still in their initial stage. Research on working mechanism of the reinforcement parts in the composite shoring structure (except deep mixing pile) has even not started yet. Large-scale testing research on composite soil-nailing structure has very few researchers set foot in. Comprehensive and accurate experiments or field test data are rather limited.Research in this dissertation is expected to reveal the characteristic of internal forces and deformation of composite soil-nailing structure of deep excavation process, so as to provide scientific basis for its broad application. The research focuses of this dissertation are as follows:(1) Summarize the advantages, development, prospects of application and research present of composite soil nailing, through discussion, and analyses the deficiency of present research on the technique.(2) On the basis of analysis of working mechanism of all the parts of composite soil-nailing structure, a three-dimensional (3D) finite element model (FEM) has been developed take advantage of ANSYS 7.0. The Drucker-Prager model is chosen to analogy the nonlinearity and plasticity of soil. Soil and the deep mixing pile are simulated by 20 nodes solid element; soil nail, anchor rod, crest beam, waist beam and reinforcement are simulated by 2 nodes 3D beam element; the shotcrete slope face is simulated by 3 nodes 3D shell element; the adhere-slip behaviors between soil nail, anchor rod, crest beam, waist beam, reinforcement, shotcrete slope face and soil are simulated by contact element. The staged excavation and retaining can also be simulated in this model. An engineering case is, as an example, analyzed and predicted internal force and deformation of every parts of the composite soil-nailing structure at various stages of excavation.(3) Field tests of composite soil-nailing structure have been carried out in two foundation pits in Guangzhou, and abundant of data have been obtained. The comprehensive analysis of themeasurements further reveals the characteristic of internal forces and deformation of composite soil-nailing structure of deep excavation process, and provides practical data for the verification of design and theoretical analysis.Finite element analysis method have widely used to analyze geotechnical engineering problem as powerful means for simulated calculation, but not perfect yet, because of difficulty in the definition of constitutive model of soil and its parameters. However, the method is valuable in the analysis of working behaviors of geotechnical engineering structure, if an appropriate model is chosen. On the other side, a large number of data obtained through experiments and field tests will verify the reliability of finite element analysis, and calibrate the model parameters, so as to promote the development of finite element analysis method. The method not only can predict the internal force and deformation of soil, soil nail, shotcrete slope face and reinforcement parts in a composite soil-nailing structure, a更多还原