本文選題：島狀多年凍土 + 橋梁樁基礎(chǔ)�。� 參考：《東北林業(yè)大學(xué)》2015年博士論文

【摘要】：多年凍土與普通的土體相比具有獨(dú)特的工程性質(zhì),凍土地區(qū)的樁基礎(chǔ)施工后樁身及周圍土體在凍土地溫作用下逐漸回凍,回凍過程中樁與周圍土體逐漸聯(lián)結(jié)成一個(gè)整體共同承受外荷載作用。由于以上現(xiàn)象在進(jìn)行多年凍土地區(qū)橋梁樁基設(shè)計(jì)時(shí)也產(chǎn)生了一些難題,比如樁基的回凍時(shí)間及回凍前后樁側(cè)摩阻力變化規(guī)律尚不明確,承載力計(jì)算時(shí)凍土層中的摩阻力的取值缺乏依據(jù)等等。因此,為了準(zhǔn)確掌島狀多年凍土地區(qū)橋梁鉆孔灌注樁的回凍時(shí)間、樁基回凍前后承載力的變化,在島狀多年凍土地區(qū)選擇2個(gè)試驗(yàn)地點(diǎn),每個(gè)試驗(yàn)地點(diǎn)澆筑3根15 m長的試驗(yàn)樁,并在試驗(yàn)樁處布設(shè)溫度監(jiān)測系統(tǒng),采集樁基回凍過程中的溫度數(shù)據(jù),根據(jù)溫度監(jiān)測結(jié)果判斷樁基回凍狀態(tài),在樁基完成回凍前后分別進(jìn)行靜載與動測試驗(yàn),分析回凍前后樁基承載力、各土(巖)層的側(cè)摩阻力及樁端阻力的變化規(guī)律。監(jiān)測及試驗(yàn)結(jié)果表明：橋梁鉆孔灌注樁澆筑完成后,在水化熱、凍土地溫的耦合作用下樁基溫度呈現(xiàn)動態(tài)變化,樁基回凍后凍土上限以下的溫度趨近于所在區(qū)域的凍土地溫,試驗(yàn)樁所在區(qū)域島狀多年凍土地溫約為-1.9℃,樁基完成回凍后樁身內(nèi)部溫度與樁側(cè)lm處的土體溫度變化趨勢相同,相同深度處的溫差小于0.1℃；樁基回凍后的承載力約為回凍前承載力的1.45倍、2個(gè)試驗(yàn)地點(diǎn)處試驗(yàn)樁樁端阻力平均增幅為45.8%、回凍后各土(巖)層的樁側(cè)摩阻力也都有所增加,其中塊石夾土增加幅度為75%、巖層增加幅度在30%-46%之間、圓礫與土按不同比例組成的土層增加幅度在30%-70%,2個(gè)試驗(yàn)地點(diǎn)凍土上限以下各(巖)土平均增長率分別為49.6%和41.7%；用靜載法實(shí)測出的各土層回凍前后的樁側(cè)摩阻力值修正高應(yīng)變動測法樁-土力學(xué)模型中的土層參數(shù),計(jì)算曲線與實(shí)測曲線擬合較好,動測與靜載試驗(yàn)所得到的樁基極限承載力誤差為3.78%,試驗(yàn)結(jié)果相符合。本研究可為類似凍土條件下的樁基設(shè)計(jì)及承載力檢測提供理論依據(jù)。
[Abstract]:Permafrost has a unique engineering property compared with ordinary soil. The pile body and surrounding soil in frozen soil area are gradually frozen under the action of frozen soil temperature after the pile foundation is constructed. In the process of refreezing, the pile and the surrounding soil gradually joined together to bear the external load together. As a result of the above phenomenon in the design of bridge pile foundation in permafrost region, some difficulties have arisen, such as the freezing time of pile foundation and the variation law of pile side friction before and after refreezing. In the calculation of bearing capacity, the value of frictional resistance in frozen soil is lack of basis and so on. Therefore, in order to accurately control the refreezing time of bridge bored pile in the island permafrost region and the change of bearing capacity of pile foundation before and after refreezing, two test sites were selected in the island permafrost region. At each test site, three test piles with a length of 15 m were built, and a temperature monitoring system was set up at the test piles to collect the temperature data during the freezing process of the pile foundation, and to judge the refreezing state of the pile foundation according to the results of temperature monitoring. The static load test and dynamic test were carried out before and after the freezing of the pile foundation, and the variation rules of bearing capacity, lateral friction and pile tip resistance of each soil (rock) layer before and after refreezing were analyzed. The results of monitoring and test show that the temperature of pile foundation changes dynamically under the coupling action of hydration heat and frozen earth temperature, and the temperature below the upper limit of frozen soil after the pile foundation is frozen is approaching to the frozen soil temperature of the region after the bridge bored cast-in-place pile is completed, and the results show that the pile foundation temperature changes dynamically under the coupling action of hydration heat and frozen soil temperature. The soil temperature of the island permafrost is about -1.9 鈩，

本文編號：2021320