【作者】 郑俊杰；

【导师】 吴世明；

【作者基本信息】 浙江大学 ， 岩土工程， 2001， 博士

【摘要】 地基处理是目前土木工程中比较活跃的研究领域，复合地基理论近十多年，得到了较大的发展。但是由于复合地基中设置的增强体材料不同、强度不同、发挥的效用不完全相同，因而各类复合地基的机理也就不相同，这就导致各类复合地基的承载力计算方法、沉降计算方法各不相同。 本文对于复合地基的承载特性及设计方法进行了较系统的研究。 首先，对现有散体材料桩的极限承载力计算公式进行了讨论，提出了修正的被动土压力法，使计算结果更为合理。在工程实践及实验基础上，提出了考虑桩与桩间土横向相互作用的散体材料桩复合地基的承载力计算公式。讨论了散体材料桩复合地基沉降计算方法，给出了散体材料桩桩身变形模量的确定方法。利用参变量最小势能原理，求出了散体材料桩扩张问题的解析解。讨论了散体材料桩复合地基的一般设计方法。 其次，在分析了柔性桩的荷载传递机理后，利用弹性力学的方法，求解了柔性桩复合地基中的桩身应力，为柔性桩复合地基桩土应力比的确定提供了一种新途径。将石灰桩简化为砂井，参照非理想竖井排水理论，对石灰桩复合地基进行了固结分析。在进行了石灰桩复合地基静载荷试验的基础上，得到石灰桩复合地基中桩土分担荷载比、桩土应力比、桩体比例界限及静载试验时沉降比取值。在阐明了石灰桩复合地基的作用机理后，提出了石灰桩在新回填土地基及非均匀地基上的设计方法，给出了加固填土的折减系数和加固非均匀地基的影响系数，讨论了石灰桩复合地基的沉降计算方法。当采用静力触探检测桩身强度及桩间土强度时，文中给出了桩土应力比的计算式，从而勿需进行复合地基静载荷试验及进行加固效果的评价。本文对深层搅拌水泥土桩设计和施工中存在的问题进行了讨论。 第三，讨论了刚性桩复合地基的设计思想，在软土地区进行了粉煤灰混凝土桩复合地基在不同压板下的静载荷试验，确定了桩间土承载力发挥系数。通过不同厚度褥垫层的试验，结合工程实践，得到刚性桩复合地基褥垫层的合理厚度，讨论了刚性桩复合地基的承载力计算方法、沉降计算方法以及刚性桩复合地基设计参数的选取问题。对粉煤灰混凝土桩桩体材料进行了配比试验，同时对粉煤灰混凝土桩在软土地区的施工工艺进行了研究。对刚性桩复合地基承载力的概率特性进行了分析。讨论了带褥垫层刚性桩复合地基的抗震机理。 最后，提出了多元复合地基的新概念，将多元复合地基分为两大类，并根据面积加权的原理，提出了两类多元复合地基的承载力计算方法。针对两类多元复合地浙江大学博士学位论文 复合地基承载特性分析及设计方法研究 郑俊杰2001年5月基的不同受力机理，提出了沉降计算方法。提出了多元复合地基的检测方法。从而建立了多元复合地基较完整的理论体系。更多还原

【Abstract】 Ground improvement is a very vivid research field in civil engineering at present .The theory of composite foundation is greatly developed in recent more than ten years . Because the material , strength and effect are not same for the different reinforced pile body installed in composite foundation , the work mechanism of all kinds of composite foundation are different . It leads to that the computation methods of bearing capacity and settlement of all kinds of composite foundation are different.The bearing capacity characteristics and design methods of composite foundation are systematically studied in this dissertation .At first , the computation formulas of the ultimate bearing capacity of the granular material pile are discussed .The modified passive earth pressure method is put forward , it make the results more reasonable . Based on engineering practice and experiment , considering the lateral interaction of the pile and soil between piles , the computation formula of bearing capacity of granular material pile is proposed .The computation method of settlement of granular material pile is discussed ,the determining method of pile body modulus of deformation of granular material pile is given .By the parametric potential energy variational principle ,the analytic solution of expansion problem of granular material pile is obtained .The common design methods of granular material pile composite foundation are discussed .Secondly , after analyzing the load transmission mechanism of flexible pile , by the theory of elasticity , the stress of pile body of flexible pile composite foundation is solved , it provides a new path for determining the pile-soil stress ratio of flexible composite foundation . After the lime-flyash pile is simplified as sand drain, according to the drainage theory of non-ideal vertical drain , the consolidation characteristics of lime-flyash pile composite foundation is analyzed. Based on the static load test of lime-flyash pile composite foundation , the load bearing ratio of pile and soil , pile-soil stress ratio , proportional limit of pile body and relative deformation value select of static load test are obtained . After the work mechanism of lime-flyash pile composite foundation is stated , the design methods of lime-flyash pile in new fill soil and non-homogeneous subsoil are put forward , the reduced coefficient of improving fill soil and non-homogeneous influence coefficient of improving non-homogeneous subsoil aregiven .The computation method of settlement for lime-flyash pile composite foundation is also proposed . When the strength of lime-flyash pile body and soil between piles are tested by static cone penetration test ,the computation formula of pile-soil stress ratio is proposed , so the improvement effect can be evaluated without static load test of composite foundation . Some existing problems in design and construction of deep mixed-in-place cement pile are also discussed .Thirdly , the design thought of rigid pile composite foundation is discussed . Based on the static load test of flyash concrete pile composite foundation with bearing plates of different dimension in soft soil region , the mobilization coefficient of the bearing capacity of soils, between piles is determined. By the experiments of sand or gravel cushion with different thickness , along with engineering practice, the proper thickness of sand or gravel cushion is proposed in rigid pile composite foundation . The computation methods of bearing capacity , settlement and select of parameter in rigid pile composite foundation design are discussed .The compound proportion tests of pile body material of flyash concrete pile are carried out .The construction technology of flyash concrete pile in soft soil region is studied .The probability characteristics of bearing capacity of rigid pile composite foundation is analyzed . The earthquake resistant mechanism of rigid pile composite foundation with sand or gravel cushion is discussed .At last, the new concept of multi-element composite foun更多还原