【摘要】：分析基坑工程中影響土體抗剪強(qiáng)度指標(biāo)的幾個(gè)重要因素,選取基坑降水前后的土樣和基坑開(kāi)挖后基坑側(cè)壁的土樣,采用直接剪切儀和三軸儀分別進(jìn)行了土樣的抗剪強(qiáng)度試驗(yàn),根據(jù)試驗(yàn)結(jié)果分析降水、基坑開(kāi)挖、不同試驗(yàn)方法對(duì)基坑工程中土體抗剪強(qiáng)度指標(biāo)的影響;采用大型通用有限元軟件Abaqus來(lái)模擬基坑在不同試驗(yàn)組結(jié)果下基坑中側(cè)壁及支護(hù)結(jié)構(gòu)的應(yīng)力狀態(tài)和變形情況。利用規(guī)范中推薦的基坑中土壓力的計(jì)算公式針對(duì)不同試驗(yàn)組結(jié)果分別計(jì)算基坑側(cè)壁土壓力,進(jìn)行基坑支護(hù)結(jié)構(gòu)樁長(zhǎng)計(jì)算和配筋計(jì)算,比較分析不同試驗(yàn)組結(jié)果值對(duì)基坑支護(hù)結(jié)構(gòu)設(shè)計(jì)的影響。通過(guò)上述工作得出基坑工程中抗剪強(qiáng)度指標(biāo)不同的選取方法對(duì)基坑工程安全及穩(wěn)定性的影響規(guī)律(1)針對(duì)具有降水措施的基坑工程設(shè)計(jì)時(shí),采用降水前的基坑土樣進(jìn)行試驗(yàn),設(shè)計(jì)計(jì)算時(shí)應(yīng)適當(dāng)提高試驗(yàn)結(jié)果值的黏聚力大小,否則會(huì)造成不必要的浪費(fèi);(2)三軸試驗(yàn)中改變圍壓與常規(guī)圍壓作用下所得的抗剪強(qiáng)度指標(biāo)值大小存在差異,土樣的黏聚力值差異較大,兩組對(duì)比試驗(yàn)值用于基坑支護(hù)結(jié)構(gòu)設(shè)計(jì),所得計(jì)算結(jié)果相近;(3)直剪試驗(yàn)和三軸試驗(yàn)所得的抗剪強(qiáng)度指標(biāo)值存在差異,三軸剪切儀試驗(yàn)條件更加接近土樣的受力變形狀態(tài),有三軸設(shè)備的前提下基坑設(shè)計(jì)計(jì)算的抗剪強(qiáng)度指標(biāo)值應(yīng)選取三軸試驗(yàn)值。
[Abstract]:Several important factors affecting the shear strength of soil in foundation pit engineering are analyzed. Soil samples before and after foundation pit dewatering and soil samples on the side wall of foundation pit after excavation are selected, and the shear strength tests of soil samples are carried out by means of direct shear meter and triaxial apparatus, respectively. According to the test results, the influence of dewatering, excavation of foundation pit and different test methods on the shear strength index of soil in foundation pit engineering is analyzed. The stress state and deformation of the side wall and supporting structure of foundation pit under different test groups were simulated by using the large and universal finite element software Abaqus. According to the results of different test groups, the soil pressure of side wall of foundation pit is calculated according to the formula of earth pressure in foundation pit, which is recommended in the code, and the pile length and reinforcement of foundation pit supporting structure are calculated. The effect of the results of different test groups on the design of foundation pit support structure is compared and analyzed. Based on the above work, the influence of different shear strength indexes on the safety and stability of foundation pit engineering is obtained. (1) in the design of foundation pit with dewatering measures, soil samples of foundation pit before dewatering are used to test. When designing and calculating, the cohesion force of the test result should be increased properly, otherwise it will cause unnecessary waste. (2) in triaxial test, there are differences between the values of shear strength index under the action of confining pressure and conventional confining pressure, and the cohesive force of soil sample is quite different. The two groups of comparative test values are used in the design of foundation pit support structure, and the calculated results are similar. (3) the shear strength index values of direct shear test and triaxial test are different, and the test conditions of triaxial shear meter are closer to the deformation state of soil sample. The triaxial test value should be selected for the shear strength index of foundation pit design and calculation on the premise of triaxial equipment.
【學(xué)位授予單位】：吉林建筑大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TU753;TU432

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