【作者】 姜陈钊；

【导师】 刘汉龙； 温学钧；

【作者基本信息】 河海大学 ， 岩土工程， 2004， 硕士

【摘要】 本文针对现浇混凝土薄壁管桩(简称PCC桩)这种新桩型，在前人工作的基础上，通过室内试验对桩体材料的强度特性进行了研究；引入了荷兰开发的大型岩土工程有限元软件PLAXIS程序，对PCC单桩承载特性进行了研究，着重分析了桩长、桩径、桩土刚度比等因素对单桩承载特性的影响。主要完成了如下工作： 1．通过试验研究了废钢渣作为原材料配制混凝土的方法，并将钢渣混凝土与普通混凝土在配制过程中的某些性质指标作了比较，分析了其原因，并在试验的基础上建立了强度与灰水比经验公式，为工程设计提供了依据。配制出的钢渣混凝土力学性能比普通混凝土力学性能要高，而且节省了水泥和石子，具有很好的经济效益。由于利用了废物，变废为宝，解决了环境污染问题，故又有很好的社会效益。 2．引入了PLAXIS程序，对PLAXIS程序的特点、计算分析原理进行了概述，对土体的三轴试验和侧限固结试验进行了模拟，计算结果较好的反应了土体的基本特性，并与试验结果符合良好。同时列举工程实例，应用MC模型进行静载荷试验的模拟，计算结果和实测结果符合良好，验证了程序在实际工程应用中的可靠性。理论和实践都证明，PLAXIS程序完全可以应用于岩土工程的科研分析。 3．应用PLAXIS程序模拟单桩静载荷试验的过程，并根据计算结果较为详细的分析了PCC单桩的基本承载特性，主要包括荷载—沉降曲线的特征、桩壁内外侧摩阻力的分布、桩端阻力的分布、桩的轴向荷载传递以及孔压消散规律等。然后从桩长、桩径以及桩土刚度比等角度分析了其对单桩承载力、内外侧摩阻力、桩端平面应力分布、轴向荷载传递、桩身截面位移等的影响。主要得出了如下一些结论：(1)对于长桩，承载力设计宜按变形控制；相同荷载下，外摩阻力随着桩长的增加而减小，内摩阻力发挥的相对长度随着桩长的增加也减小；在桩端平面上，桩壁处受到附加压应力，而两侧的土体中有附加拉应力，在离桩心较远处，附加应力的影响已经很小，几乎为零。(2)随着桩径的增大，桩的极限承载力有显著提高；在相同的荷载密度下，随着桩径的增加，外侧摩阻力几乎没有变化而内摩阻力却有显著提高，并且内摩阻力的发挥长度也随着桩径的增大而增长。(3)在桩土刚度比较小时，桩外侧摩阻力呈抛物线分布，沿着桩顶向下迅速增大，达到最大值后再沿着桩深有迅速减小的趋势；桩壁内摩阻力沿着桩身向下逐渐增大，达到最大值后持续减小至零，以下一段桩身继续减小至负值，在该段为负摩擦区，然后再逐渐增大至零或正值。更多还原

【Abstract】 Based on the work of former researchers, the mechanical properties of the material of the pipe pile are studied in this thesis by indoor experiment; also the bearing mechanism is analysed combined with the famous geotechnical FEM software PLAXIS and the influences of length of pile, diameter and the ratio of the stiffness of pile to the stiffness of soil on the bearing mechanism are discussed. For details ,the main contents are as follow:1.The research is conducted on the confecting method of steel-slag concrete by indoor experiment. Through comparison of the physical and mechanical properties between steel-slag concrete and plain concrete, it can analyze the advantages of using steel-slag concrete. Based on the test results, empirical formulae is developed, which provides some bases for practical projects. The mechanical properties of steel-slag concrete prevails more advantages than the plain concrete, also the quantities of cement and gravel are reduced, consequently reducing the capital cost of the project materials, so this method is economically and safely to be used and it can solve the environmental problems of unused steel-slag.2.The FEM software PLAXIS is introduced and its theories and numerical methods are given. The standard drained triaxial test and the oedometer test are subjected to simulations of various laboratory tests in order to validate the reliability with measured test data. Also the load-settlement curves by field test and FEM on a practical engineering are compared. The reliability is validated further on.3.The static loading test is modeled by PLAXIS , based on this, the basic bearing mechanism is analysed which comprise the rule of the load-settlement curves, inner and outer friction resistance, end bearing , stress distribution along pile depth and the dissipation of excess pore pressures. Also the influences of the length, diameter, and the ratio of the stiffness of pipe to the stiffness of soil on the bearing mechanisms are discussed. Based on these, some useful conclusions are reached.更多还原