承壓水降水引起深基坑變形研究
發(fā)布時(shí)間：2019-07-03 09:39
【摘要】：隨著城市地下空間的開發(fā)利用和城市軌道交通工程建設(shè)的快速發(fā)展,深基坑開挖越來越深,承壓水治理在基坑工程中的地位逐漸上升。本文采用解析計(jì)算方法建立了基坑邊坡滑動(dòng)時(shí)安全系數(shù)的解析算式,利用地質(zhì)雷達(dá)探測了地鐵車站基坑的地質(zhì)情況,明確了地下水的分布,結(jié)合地質(zhì)勘察報(bào)告和現(xiàn)場實(shí)測數(shù)據(jù)利用智能位移反分析確定了承壓含水層地質(zhì)參數(shù)的取值,最后利用FLAC3D模擬分析了不同滲流特征下承壓水降水引起的深基坑變形特點(diǎn)。本文主要得到以下結(jié)論:(1)采用解析計(jì)算方法,建立了基坑邊坡平面滑動(dòng)和圓弧滑動(dòng)時(shí)安全系數(shù)的解析算式,計(jì)算得出了所研究基坑豎直邊坡圍護(hù)結(jié)構(gòu)的最小深度應(yīng)為25.38m。(2)采用地質(zhì)雷達(dá)對所研究地鐵車站施工場地的地質(zhì)情況進(jìn)行了探測。發(fā)現(xiàn)所測區(qū)域存在土體疏松或脫空現(xiàn)象,且從地下2m處有開始出現(xiàn)地下水的跡象。根據(jù)現(xiàn)場監(jiān)測數(shù)據(jù)對地表沉降、地下連續(xù)墻側(cè)移、基坑坑底隆起進(jìn)行了處理分析,總結(jié)了基坑變形規(guī)律。(3)采用正交試驗(yàn)法分析了承壓含水層不同參數(shù)對基坑外圍土體沉降的敏感性,確定了承壓含水層需要反演的4個(gè)參數(shù):彈性模量E、泊松比?、滲透系數(shù)K、孔隙率n。采用均勻試驗(yàn)法構(gòu)建反演分析的學(xué)習(xí)樣本和測試樣本,利用MATLAB神經(jīng)網(wǎng)絡(luò)工具箱對試驗(yàn)樣本進(jìn)行學(xué)習(xí)和測試得出符合誤差要求的訓(xùn)練函數(shù),結(jié)合實(shí)測數(shù)據(jù)通過反演得出承壓含水層的參數(shù)取值。進(jìn)行正演試驗(yàn),結(jié)果表明:數(shù)值計(jì)算值與相應(yīng)的現(xiàn)場實(shí)測值最大相對誤差為7.89%,吻合度較高,能夠滿足工程精度的需要。(4)根據(jù)基坑底板抗突涌計(jì)算公式,得出車站基坑在開挖施工前必須降低承壓水水頭9m。承壓水降水導(dǎo)致基坑外圍土體出現(xiàn)“拋物線”狀沉降變形,在距離基坑2倍開挖深度時(shí)沉降值達(dá)到最大。沉降變化趨勢與降水漏斗形式相似,證明在最大沉降處外側(cè)土體的沉降是由于降水引起的。承壓水降壓引起的沉降變形主要發(fā)生在承壓含水層上覆土體中,其沉降變形呈現(xiàn)“上小下大”特點(diǎn),土體的最大位移發(fā)生在承壓含水層與上覆土體分界處。(5)根據(jù)圍護(hù)結(jié)構(gòu)的不同將基坑承壓水降水時(shí)滲流特征分為三類。在第一類滲流特征下,承壓水降水引起的土體沉降相對最小。第二類滲流特征下土體沉降變形最大,比同等圍護(hù)方案下坑內(nèi)降水方案導(dǎo)致的最大沉降變形大141%。在第三類滲流特征下,隨著地下連續(xù)墻插入承壓含水層深度的增加,基坑周圍地表沉降減小。深基坑地下連續(xù)墻的側(cè)移和坑底隆起主要由支護(hù)結(jié)構(gòu)剛度和開挖土體深度決定,承壓水降水導(dǎo)致的影響相對較小。地下連續(xù)墻側(cè)移最大值發(fā)生在基坑坑底附近,基坑底部的隆起呈現(xiàn)中心大兩邊小的特點(diǎn)。
[Abstract]:With the development and utilization of urban underground space and the rapid development of urban rail transit engineering, the excavation of deep foundation pit is getting deeper and deeper, and the position of confined water treatment in foundation pit engineering is gradually rising. In this paper, the analytical formula of safety factor of foundation pit slope sliding is established by means of analytical calculation method, the geological condition of foundation pit of subway station is detected by geological radar, the distribution of groundwater is clarified, and the value of geological parameters of confined aquifer is determined by intelligent displacement back analysis combined with geological survey report and field measured data. Finally, FLAC3D simulation is used to analyze the deformation characteristics of deep foundation pit caused by pressure water drop under different seepage characteristics. The main conclusions of this paper are as follows: (1) by using the analytical calculation method, the analytical formulas of the safety factor of the plane sliding and circular arc sliding of the foundation pit slope are established, and it is calculated that the minimum depth of the vertical slope envelope structure of the studied foundation pit should be 25.38. (2) the geological conditions of the construction site of the studied subway station are detected by using geological radar. It is found that the soil is loose or empty in the measured area, and there are signs of groundwater beginning from 2m underground. According to the field monitoring data, the surface settlement, the lateral displacement of underground continuous wall and the uplift at the bottom of foundation pit are treated and analyzed, and the deformation law of foundation pit is summarized. (3) the sensitivity of different parameters of confined aquifer to the settlement of soil around foundation pit is analyzed by orthogonal test method, and four parameters that need to be inversed in confined aquifer are determined: elastic modulus E, Poisson's ratio? permeability coefficient K, porosity n. The uniform test method is used to construct the learning samples and test samples of inversion analysis, and the MATLAB neural network toolbox is used to study and test the test samples to obtain the training function that meets the error requirements. Combined with the measured data, the parameters of the confined aquifer are obtained by inversion. The results show that the maximum relative error between the numerical calculation value and the corresponding field measured value is 7.89%, and the coincidence degree is high, which can meet the needs of engineering accuracy. (4) according to the anti-surge calculation formula of foundation pit floor, it is concluded that the confined water head must be reduced by 9 m before excavation. The "parabola" settlement deformation of the soil around the foundation pit is caused by the pressure water dewatering, and the settlement value reaches the maximum when it is twice the excavation depth of the foundation pit. The change trend of settlement is similar to that of precipitation funnel, which proves that the settlement of lateral soil at the maximum settlement is caused by precipitation. The settlement deformation caused by confined water pressure reduction mainly occurs in the overlying soil of confined aquifer, and its settlement deformation is "small and small". The maximum displacement of soil occurs at the boundary between confined aquifer and overlying soil. (5) according to the difference of enclosure structure, the seepage characteristics of foundation pit under pressure water dewatering are divided into three categories. Under the first kind of seepage characteristics, the settlement of soil caused by confined water drop is relatively small. The settlement deformation of soil under the characteristics of the second kind of seepage is the largest, which is 141% larger than that caused by the precipitation scheme in the pit under the same enclosure scheme. Under the third kind of seepage characteristics, the surface settlement around the foundation pit decreases with the increase of the depth of the confined aquifer inserted into the underground continuous wall. The lateral movement of the underground continuous wall and the uplift of the bottom of the pit are mainly determined by the stiffness of the supporting structure and the depth of the excavated soil, but the influence caused by the pressure water precipitation is relatively small. The maximum lateral displacement of the underground continuous wall occurs near the bottom of the foundation pit, and the uplift at the bottom of the foundation pit shows the characteristics of the large and small sides of the center.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU753
本文編號：2509282
[Abstract]:With the development and utilization of urban underground space and the rapid development of urban rail transit engineering, the excavation of deep foundation pit is getting deeper and deeper, and the position of confined water treatment in foundation pit engineering is gradually rising. In this paper, the analytical formula of safety factor of foundation pit slope sliding is established by means of analytical calculation method, the geological condition of foundation pit of subway station is detected by geological radar, the distribution of groundwater is clarified, and the value of geological parameters of confined aquifer is determined by intelligent displacement back analysis combined with geological survey report and field measured data. Finally, FLAC3D simulation is used to analyze the deformation characteristics of deep foundation pit caused by pressure water drop under different seepage characteristics. The main conclusions of this paper are as follows: (1) by using the analytical calculation method, the analytical formulas of the safety factor of the plane sliding and circular arc sliding of the foundation pit slope are established, and it is calculated that the minimum depth of the vertical slope envelope structure of the studied foundation pit should be 25.38. (2) the geological conditions of the construction site of the studied subway station are detected by using geological radar. It is found that the soil is loose or empty in the measured area, and there are signs of groundwater beginning from 2m underground. According to the field monitoring data, the surface settlement, the lateral displacement of underground continuous wall and the uplift at the bottom of foundation pit are treated and analyzed, and the deformation law of foundation pit is summarized. (3) the sensitivity of different parameters of confined aquifer to the settlement of soil around foundation pit is analyzed by orthogonal test method, and four parameters that need to be inversed in confined aquifer are determined: elastic modulus E, Poisson's ratio? permeability coefficient K, porosity n. The uniform test method is used to construct the learning samples and test samples of inversion analysis, and the MATLAB neural network toolbox is used to study and test the test samples to obtain the training function that meets the error requirements. Combined with the measured data, the parameters of the confined aquifer are obtained by inversion. The results show that the maximum relative error between the numerical calculation value and the corresponding field measured value is 7.89%, and the coincidence degree is high, which can meet the needs of engineering accuracy. (4) according to the anti-surge calculation formula of foundation pit floor, it is concluded that the confined water head must be reduced by 9 m before excavation. The "parabola" settlement deformation of the soil around the foundation pit is caused by the pressure water dewatering, and the settlement value reaches the maximum when it is twice the excavation depth of the foundation pit. The change trend of settlement is similar to that of precipitation funnel, which proves that the settlement of lateral soil at the maximum settlement is caused by precipitation. The settlement deformation caused by confined water pressure reduction mainly occurs in the overlying soil of confined aquifer, and its settlement deformation is "small and small". The maximum displacement of soil occurs at the boundary between confined aquifer and overlying soil. (5) according to the difference of enclosure structure, the seepage characteristics of foundation pit under pressure water dewatering are divided into three categories. Under the first kind of seepage characteristics, the settlement of soil caused by confined water drop is relatively small. The settlement deformation of soil under the characteristics of the second kind of seepage is the largest, which is 141% larger than that caused by the precipitation scheme in the pit under the same enclosure scheme. Under the third kind of seepage characteristics, the surface settlement around the foundation pit decreases with the increase of the depth of the confined aquifer inserted into the underground continuous wall. The lateral movement of the underground continuous wall and the uplift of the bottom of the pit are mainly determined by the stiffness of the supporting structure and the depth of the excavated soil, but the influence caused by the pressure water precipitation is relatively small. The maximum lateral displacement of the underground continuous wall occurs near the bottom of the foundation pit, and the uplift at the bottom of the foundation pit shows the characteristics of the large and small sides of the center.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU753
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