【作者】 杨寿松；

【导师】 刘汉龙；

【作者基本信息】 河海大学 ， 岩土工程， 2005， 硕士

【摘要】 现浇混凝土薄壁管桩(简称PCC桩)及其复合地基是一种全新的地基处理新技术，该技术在地基加固效果、施工工期、工程造价和环保等方面与传统地基处理方法相比具有较大的优越性，因此在地基处理中具有广阔的应用前景。本文通过该项新技术在盐通高速公路软基处理中的应用，对这种地基处理新技术的施工工艺、成桩过程中的质量控制措施及成桩质量检测方法、设计理论、承载特性和变形特性进行了研究，并对加固效果进行了评价。完成的主要工作包括以下几个方面： (1) 对PCC桩的研制背景、设计原则、沉桩工艺、工作原理以及成桩机理进行了述评，阐述了PCC管桩技术优点。并对目前其主要设计方法进行了归纳。 (2) 通过现场试验，对PCC桩施工工艺、成桩过程中的质量控制措施、桩体施工对周围环境的影响以及成桩质量检测方法进行了研究，得出了一些有益的结论，可作为技术经验在类似的工程中进行推广应用。 (3) 通过静载荷试验对PCC单桩及其复合地基的承载特性做了初步探讨，重点分析了PCC单桩的沉降曲线的特点，将其沉降曲线分为弹性沉降阶段和弹塑性沉降阶段。指出桩体受荷后首先进入弹性沉降阶段，此时荷载与桩体沉降呈线性关系；随着沉降的逐渐增大，桩侧摩阻力也逐渐增大，当桩体沉降达到弹性极限沉降量时，桩侧阻力达到了最大值，此后桩体进入弹塑性沉降阶段．提出可以用双曲线拟合PCC单桩弹塑性沉降阶段的荷载—沉降关系，并可通过外推法近似求得PCC桩的承载力，为快速确定PCC单桩承载力提供了一种简便的方法。 (4) 结合现场堆载期间测得的相关数据对PCC桩复合地基处理软基的实际效果以及其在路堤荷载作用下的承载性状和变形特性做了初步分析。 (5) 通过对不同桩径、壁厚、桩距以及不同垫层管桩复合地基加固效果的比较，对PCC桩复合地基的桩径、桩距、壁厚等设计参数进行了探讨，基于加固效果、施工便利性和经济利益考虑，给出了PCC桩复合地基适宜的壁厚和桩距等设计参数。 (6) 通过理论计算和静载荷试验数据的比较，分析了PCC桩的受荷性状，提出了PCC桩承载力的计算方法。 (7) 结合现场沉降观测数据的验证，得出了复合地基沉降计算的复合模量法不适合于现浇薄壁管桩复合地基的结论，肯定了按桩土实际荷载分担进行沉降计算的应力比法对PCC桩复合地基的有效性。更多还原

【Abstract】 As a new foundation improvement technology, the cast-in-situ concrete thin-wall pipe pile (PCC pile) has greater superiority over traditional method of foundation improvement in the effect of improvement, construction time limit, cost of engineering and environment protection etc. Therefore it has a great prospect of application in foundation improvement. Based on the application of this new technology in soft soil improvement of Yan-Tong expressway, the construction techniques of this new technology, method of quality control during construction, method of quality detecting of PCC pile, calculation theory, characteristic of loading and deformation are studied in the thesis. The effect of foundation improvement is also analyzed in the paper. For details, the main contents are as follows:1.The background of manufacture, principle of design, construction techniques of pile sinking, theory of working and mechanism of construction of PCC pile are analyzed in details. Advantages of PCC pile are also evaluated and the main methods of design at present are gathered.2. The construction techniques of PCC pile, method of quality control and influence on surroundings during pile construction and method of quality detecting of PCC pile are studied and some useful conclusion are obtained through field test, which can be popularized in similar engineering as empirical technology.3. Characteristics of loading on single PCC pile and composite foundation, especially that of settlement curve of single PCC pile, which is divided in elastic settlement phase and elastic -plastic settlement phase, are studied through static load test. It is pointed out that the PCC pile enters elastic settlement phase firstly under load and the settlement has a linear relationship with load. With the increase of settlement, there also comes an increase in pile wall friction. The pile wall friction reaches the maximum when the settlement of pile achieves elastic settlement limit and the pile enters elastic-plastic settlement phase hereafter. It is proposed that the shape of the curve of load and settlement in elastic-plastic settlement phase can be simulated by hyperbola and the bearing capacity of PCC pile can be obtained by extrapolation, which offers a simple method to determine the bearing capacity of PCC pile.4. The characteristics of bearing and deformation under embankment load and the effect of soft soil improvement of PCC pile composite foundation are analyzed based on the related datum obtained during load on the spot.5.The parameter of pile diameter, space between piles, thickness of pile wall are discussed through comparing with the effect of PCC pile composite foundation on the basis of different pile diameter, space between piles, thickness of pile wall and bed course.6.Characters of bearing of PCC pile are analyzed and the calculation method of bearing capacity of PCC pile is proposed through comparing the result of theoretical calculation with the datum of static load test.7.The result that the method of composite modulus does not fits the settlement calculation of PCC pile composite foundation is obtained and the effectiveness of stress ratio method for the settlement calculation of PCC pile composite foundation based on the real share in total load of pile and soil is affirmed by means of verification of the test settlement datum.更多还原