多年冻土区公路CFG桩—筏复合地基承载力研究
发布时间：2018-11-08 07:11
【摘要】：东北地区的冻土多为岛状多年冻土,其力学及传热学方面的不稳定性对此地区建筑物的稳定性造成了极大的威胁。以往在岛状多年冻土地区修筑的公路都遭受了沉降、开裂、冻胀等不同程度的破坏,如何解决这些问题已经成为国内外诸多研究学者的首要问题。 本文以黑龙江省伊绥高速公路的岛状多年冻土路基段为依托工程,将CFG桩-筏板复合地基与岛状多年冻土相结合,利用CFG桩-筏板复合地基对修筑在高纬度岛状多年冻土地区的高速公路路基进行处理。同时对CFG桩-筏板复合地基进行承载力测试及有限元分析,主要研究内容和成果如下： (1)根据CFG桩及多年冻土特性制定了CFG桩试验场方案,进行了CFG单桩及桩周多年冻土的温度分布规律测试。测试结果表明,CFG单桩施工后,对桩周冻土的影响较小,桩周土很快回冻。CFG单桩与冻土相互作用后共同承担静载,桩端反力较小,CFG单桩承载力主要是由桩侧多年冻土提供的冻结力承担,冻土的CFG桩是典型的摩擦桩,加载初期桩端反力与沉降的关系呈非线性,沉降值的发展速度快于桩端反力增长值,桩体发生部分弹性压缩,使桩顶位移增加较快。 (2)根据CFG单桩试验结果,结合黑龙江省伊绥高速公路岛状多年冻土路基试验段现场工程实际情况,确定CFG桩-筏复合地基承载力试验方法,对CFG桩-筏以及多年冻土的温度分布规律进行了测试；测试结果表明,桩-筏共同作用下桩周冻土回冻缓慢。 (3)对CFG桩-筏复合地基在高纬度岛状多年冻土条件下的承载力特性进行了路堤荷载试验,试验结果表明,路堤荷载试验作用下CFG桩-筏复合地基中的CFG桩与单桩受力模式不同,六级加载之后桩端反力增长值与沉降值基本呈线性关系；CFG桩-筏复合地基中的CFG桩端反力占荷载的50%以上。 (4)利用有限元软件ABAQUS建立了CFG单桩模型,并进行了数值模拟分析,得出了CFG单桩在岛状多年冻土中承载力的变化特点。通过分析CFG单桩在不同荷载作用下桩体与多年冻土的沉降特点,确定了桩体与多年冻土的弹性模量对沉降量的影响。 (5)根据CFG桩-筏以及多年冻土的温度分布测试结果,得到CFG桩侧冻土融化,桩底冻土回冻的边界条件,利用有限元软件ABAQUS建立了CFG桩-筏复合地基模型,对CFG桩、桩间土承担的荷载进行了分析,得到了桩体受力与土体受力比例关系；同时对CFG桩-筏板整体的沉降进行研究,得出整个加载过程中,CFG桩-筏板沉降较小。
[Abstract]:The permafrost in Northeast China is mostly island permafrost, and the instability in mechanics and heat transfer poses a great threat to the stability of buildings in this area. In the past, the roads built in the island permafrost region have been destroyed by settlement, cracking, frost heave and so on. How to solve these problems has become the most important problem for many scholars at home and abroad. Based on the island permafrost subgrade section of Yi-sui Expressway in Heilongjiang Province, this paper combines the CFG pile-raft composite foundation with the island permafrost. The CFG pile-raft composite foundation is used to treat the expressway roadbed in the high latitude island permafrost region. At the same time, the bearing capacity of CFG pile-raft composite foundation is tested and analyzed by finite element method. The main research contents and results are as follows: (1) according to the characteristics of CFG pile and permafrost, the scheme of CFG pile test site is established. The temperature distribution of CFG single pile and permafrost around pile is measured. The test results show that the influence of CFG single pile on the permafrost around the pile is small, and the soil around the pile is frozen quickly. After the interaction of CFG single pile and frozen soil, the static load is shared, and the reaction force at the end of the pile is small. The bearing capacity of CFG single pile is mainly borne by the freezing force provided by permafrost on the pile side. The CFG pile in frozen soil is a typical friction pile. The relationship between pile tip reaction force and settlement is nonlinear at the initial loading stage, and the settlement value develops faster than the pile end reaction force. The partial elastic compression of the pile makes the displacement of the top of the pile increase faster. (2) according to the results of CFG single pile test, combined with the field engineering practice of the island permafrost roadbed test section of Yi-Sui Expressway in Heilongjiang Province, the bearing capacity test method of CFG pile-raft composite foundation is determined. The temperature distribution of CFG pile-raft and permafrost was measured. The test results show that the frozen soil around the pile is slowly frozen under the action of pile-raft. (3) the bearing capacity of CFG pile-raft composite foundation under the condition of high latitude island permafrost is tested by embankment load test. Under the action of embankment load test, the stress mode of CFG pile in CFG pile-raft composite foundation is different from that of single pile. The reaction force at the end of CFG pile in CFG pile-raft composite foundation accounts for more than 50% of the load. (4) using the finite element software ABAQUS, the CFG single pile model is established, and the numerical simulation analysis is carried out, and the variation characteristics of the bearing capacity of the CFG single pile in the island permafrost are obtained. By analyzing the settlement characteristics of CFG single pile and permafrost under different loads, the influence of elastic modulus of pile and permafrost on settlement is determined. (5) according to the test results of CFG pile-raft and permafrost temperature distribution, the boundary conditions of permafrost thawing on the side of CFG pile and frozen soil at the pile bottom are obtained. The CFG pile-raft composite foundation model is established by using the finite element software ABAQUS. The load of soil between piles is analyzed, and the relationship between the force of pile and the force of soil is obtained. At the same time, the settlement of CFG pile-raft is studied, and it is concluded that the settlement of CFG pile-raft is small in the whole loading process.
【学位授予单位】：东北林业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U416.16
本文编号：2317751
[Abstract]:The permafrost in Northeast China is mostly island permafrost, and the instability in mechanics and heat transfer poses a great threat to the stability of buildings in this area. In the past, the roads built in the island permafrost region have been destroyed by settlement, cracking, frost heave and so on. How to solve these problems has become the most important problem for many scholars at home and abroad. Based on the island permafrost subgrade section of Yi-sui Expressway in Heilongjiang Province, this paper combines the CFG pile-raft composite foundation with the island permafrost. The CFG pile-raft composite foundation is used to treat the expressway roadbed in the high latitude island permafrost region. At the same time, the bearing capacity of CFG pile-raft composite foundation is tested and analyzed by finite element method. The main research contents and results are as follows: (1) according to the characteristics of CFG pile and permafrost, the scheme of CFG pile test site is established. The temperature distribution of CFG single pile and permafrost around pile is measured. The test results show that the influence of CFG single pile on the permafrost around the pile is small, and the soil around the pile is frozen quickly. After the interaction of CFG single pile and frozen soil, the static load is shared, and the reaction force at the end of the pile is small. The bearing capacity of CFG single pile is mainly borne by the freezing force provided by permafrost on the pile side. The CFG pile in frozen soil is a typical friction pile. The relationship between pile tip reaction force and settlement is nonlinear at the initial loading stage, and the settlement value develops faster than the pile end reaction force. The partial elastic compression of the pile makes the displacement of the top of the pile increase faster. (2) according to the results of CFG single pile test, combined with the field engineering practice of the island permafrost roadbed test section of Yi-Sui Expressway in Heilongjiang Province, the bearing capacity test method of CFG pile-raft composite foundation is determined. The temperature distribution of CFG pile-raft and permafrost was measured. The test results show that the frozen soil around the pile is slowly frozen under the action of pile-raft. (3) the bearing capacity of CFG pile-raft composite foundation under the condition of high latitude island permafrost is tested by embankment load test. Under the action of embankment load test, the stress mode of CFG pile in CFG pile-raft composite foundation is different from that of single pile. The reaction force at the end of CFG pile in CFG pile-raft composite foundation accounts for more than 50% of the load. (4) using the finite element software ABAQUS, the CFG single pile model is established, and the numerical simulation analysis is carried out, and the variation characteristics of the bearing capacity of the CFG single pile in the island permafrost are obtained. By analyzing the settlement characteristics of CFG single pile and permafrost under different loads, the influence of elastic modulus of pile and permafrost on settlement is determined. (5) according to the test results of CFG pile-raft and permafrost temperature distribution, the boundary conditions of permafrost thawing on the side of CFG pile and frozen soil at the pile bottom are obtained. The CFG pile-raft composite foundation model is established by using the finite element software ABAQUS. The load of soil between piles is analyzed, and the relationship between the force of pile and the force of soil is obtained. At the same time, the settlement of CFG pile-raft is studied, and it is concluded that the settlement of CFG pile-raft is small in the whole loading process.
【学位授予单位】：东北林业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U416.16
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