多年凍土區(qū)公路CFG樁—筏復合地基承載力研究
發(fā)布時間：2018-11-08 07:11
【摘要】：東北地區(qū)的凍土多為島狀多年凍土,其力學及傳熱學方面的不穩(wěn)定性對此地區(qū)建筑物的穩(wěn)定性造成了極大的威脅。以往在島狀多年凍土地區(qū)修筑的公路都遭受了沉降、開裂、凍脹等不同程度的破壞,如何解決這些問題已經(jīng)成為國內(nèi)外諸多研究學者的首要問題。 本文以黑龍江省伊綏高速公路的島狀多年凍土路基段為依托工程,將CFG樁-筏板復合地基與島狀多年凍土相結(jié)合,利用CFG樁-筏板復合地基對修筑在高緯度島狀多年凍土地區(qū)的高速公路路基進行處理。同時對CFG樁-筏板復合地基進行承載力測試及有限元分析,主要研究內(nèi)容和成果如下： (1)根據(jù)CFG樁及多年凍土特性制定了CFG樁試驗場方案,進行了CFG單樁及樁周多年凍土的溫度分布規(guī)律測試。測試結(jié)果表明,CFG單樁施工后,對樁周凍土的影響較小,樁周土很快回凍。CFG單樁與凍土相互作用后共同承擔靜載,樁端反力較小,CFG單樁承載力主要是由樁側(cè)多年凍土提供的凍結(jié)力承擔,凍土的CFG樁是典型的摩擦樁,加載初期樁端反力與沉降的關(guān)系呈非線性,沉降值的發(fā)展速度快于樁端反力增長值,樁體發(fā)生部分彈性壓縮,使樁頂位移增加較快。 (2)根據(jù)CFG單樁試驗結(jié)果,結(jié)合黑龍江省伊綏高速公路島狀多年凍土路基試驗段現(xiàn)場工程實際情況,確定CFG樁-筏復合地基承載力試驗方法,對CFG樁-筏以及多年凍土的溫度分布規(guī)律進行了測試；測試結(jié)果表明,樁-筏共同作用下樁周凍土回凍緩慢。 (3)對CFG樁-筏復合地基在高緯度島狀多年凍土條件下的承載力特性進行了路堤荷載試驗,試驗結(jié)果表明,路堤荷載試驗作用下CFG樁-筏復合地基中的CFG樁與單樁受力模式不同,六級加載之后樁端反力增長值與沉降值基本呈線性關(guān)系；CFG樁-筏復合地基中的CFG樁端反力占荷載的50%以上。 (4)利用有限元軟件ABAQUS建立了CFG單樁模型,并進行了數(shù)值模擬分析,得出了CFG單樁在島狀多年凍土中承載力的變化特點。通過分析CFG單樁在不同荷載作用下樁體與多年凍土的沉降特點,確定了樁體與多年凍土的彈性模量對沉降量的影響。 (5)根據(jù)CFG樁-筏以及多年凍土的溫度分布測試結(jié)果,得到CFG樁側(cè)凍土融化,樁底凍土回凍的邊界條件,利用有限元軟件ABAQUS建立了CFG樁-筏復合地基模型,對CFG樁、樁間土承擔的荷載進行了分析,得到了樁體受力與土體受力比例關(guān)系；同時對CFG樁-筏板整體的沉降進行研究,得出整個加載過程中,CFG樁-筏板沉降較小。
[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.
【學位授予單位】：東北林業(yè)大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：U416.16
本文編號：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.
【學位授予單位】：東北林業(yè)大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：U416.16
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