【作者】 夏长华；

【导师】 李国民；

【作者基本信息】 中国地质大学（北京） ， 地质工程， 2008， 硕士

【摘要】 随着城市的发展,需要在杂填土上建设各种建筑物或修筑公路、铁路等基础设施。同时人们的环保意识也逐步提高,在进行各种建设时须处理好地基处理与环保的关系。因此研究杂填土特别是深厚杂填土地基处理技术是很有必要的。杂填土的工程性质包括:重度、含水量、孔隙率、渗透系数、剪切强度和压缩性。影响杂填土性质的因素:堆积年限、填料及其组合性质、密实程度、地下水的侵蚀和下卧层岩性。在选择杂填土处理方法时应考虑杂填土场地性质不均、厚度变化大,强度低,压缩性大并有较强湿陷性、自重压密性,以及渗滤液污染土体和地下水,H2S等毒气、毒液、毒物和富集沼气对人的危害,对桩产生的负摩擦力等问题进行分析与择定,表明重锤夯扩挤密法较适宜于处理深厚杂填土。重锤夯扩挤密法能就地取材,造价低,具有绿色工程的特点;具有高动能和强挤密效应,均匀性好,地基承载力提高显著;在分层土中桩体呈串珠状,桩与桩间土呈“咬合”和“抱紧”的现象。重锤夯扩挤密法的宏观加固机理是采用高压夯击和动态冲、砸、挤压的强力压实和挤密作用,不仅使桩体十分密实,而且使桩周土受到侧向强力挤密应力,成桩后应力释放对桩体产生很大的侧向约束“抱紧”作用,使桩体具有刚、柔性桩的特点。对于分层地基或软硬不均土层,桩体在施工挤密过程中会形成串珠体,有利于桩与桩侧土的紧密“咬合”增大了侧壁摩阻力。微观加固机理是在冲击力的作用下土的结构发生持续的“聚合作用”,在土体中出现由较小的土粒沿大颗粒环向平行排列而形成的旋涡状结构,使土体的工程力学性质得到改善。土体密实由三部分组成:(1)巨大的冲击力使颗粒的“架空”结构被破坏,使孔隙体积减少;(2)在巨大的冲击力作用下,填土颗粒被剪切、破碎而互相填充、挤密,使土石体更加密实、结构更加稳定;(3)杂填土中的骨架颗粒的弹性变形引起的体积压缩。处理后的桩与桩间土形成一个密实整体,形成的复合地基不仅刚度均匀,而且承载性状显著改善。用ANSYS模型对渣土桩处理杂填土地基的处理效果进行计算分析,ANSYS模型可以较好地反映夯击时土体的位移情况,与实测结果及经验值较为一致。结合北京动车段杂填土场地渣土桩、注浆和复合载体桩处理方法的室内试验和现场测试,表明经渣土桩处理后地基承载力和沉降满足设计要求。对整个场地分区域采用覆盖和放空排气两种处理技术,能有效控制场地产生的气体。更多还原

【Abstract】 With the development of the city, various building or construct infrastructures, such as highway and railroad etc. need construct on the miscellaneous fill. People’s consciousness of environmental protection gradually raised in the meantime, the relation between ground treatment and environmental protection should be well handled. Therefore the research on the ground treatment technique of miscellaneous fill, especially for the deep miscellaneous fill, is very necessary.The engineering properties of miscellaneous fill include: unit weight, water content, porosity, coefficient of permeability, shear strength and compressibility. The influencing factors of the miscellaneous fill’s properties include: fill time, filling and theirs combination property, compactness, ground water erode and subjacent bed lithology.When choosing the ground treatment method of miscellaneous fill, people should consider that the miscellaneous fill ground has differential property, various thickness, low strength, high compressibility and strong collapsibility and self-weight consolidation, and the problems of filtration liquid polluting soil and groundwater, the H2S etc. poisonous gas, venom, poison and enrichment methane imperiling people, producing negative friction etc. . Analysis and selection result shows that the pile filler is well fit for treating deep miscellaneous fill. The pile filler can acquire material locally, have low price, and have the characteristics of green engineering; have high kinetic energy and strong compaction effect, good uniformity, evidently raise ground’s bearing capacity. The pile filler body presents the form of a string of bead in the layering soil. Pile and soil present the phenomena of "occlusion" and "enclasp". The construction goes in brief and easily.The macroscopical working mechanism of the heavy-hammer rammed-expanded compaction pile uses the high pressure and the function of dynamical thrusting, smashing and squeezing to compact the soil, which not only makes the pile body compact, but also makes the soil round the pile be subjected strong side compact strength. Strength releasing produces great side restrained "enclasp" effect after the pile forming. Therefore the pile body has the characteristics of the rigid pile and flexible pile. For the layering ground or non-uniform soil, the pile body will become a string of bead in the construction, favoring for the pile and the soil round the pile to closely "occlude" to increase side frictional resistance. The pile and the soil among the pile form compacted whole after reinforcement. The microcosmic working mechanism of the heavy-hammer rammed-expanded compaction pile is that the soil structure produces "aggregation" under wallop. The smaller soil grain parallel alignment following the big grain under wallop, the circinate structure appears in soil. This kind of structure makes the engineering mechanics property of the soil improved. The compaction of soil includes:(1)the huge impact makes the "overhead " structure of soil break and the hole volume reduce;(2)under the huge impact, the soil grain is sheared, broken up or the sharp angle broken up then filled and crowded, which makes the soil more compacted and the structure more stable(;3)The volume compression is caused by the flexibility of miscellaneous fill grain. The compound ground is not only rigidity even, but also its bearing behavior is evidently improved.Using ANSYS model to analyze the effect of pile filler treatment for miscellaneous fill, ANSYS model can well reflect the soil’s displacement during thrusting. The simulation result is consistent with measure result and experienced value.The laboratory and in-situ test did about pile filler, grouting and ram-compacted piles with bearing base in miscellaneous fill, the result shows that the field’s bearing capacity and settlement is satisfactory for design after treatment. Using cladding and discharge treatment technique in different district on the whole field can effectively control the field’s gas creation.更多还原