基于地下水位變化高層建筑群引起地層分層沉降規(guī)律研究
發(fā)布時間：2018-09-06 08:30
【摘要】：地面沉降已經(jīng)使得世界上60多個國家和地區(qū)蒙受巨大的經(jīng)濟損失,僅上海一地即高達2900多億元,平均每下降1mm造成的經(jīng)濟損失約1.53億元。本文以上海地區(qū)地面沉降為研究背景,采用理論分析、數(shù)值模擬和室內(nèi)試驗等手段,對軟土地區(qū)高層建筑荷載和地下水位變化聯(lián)合作用引起的地面沉降進行研究,為軟土地區(qū)地面沉降防治提供理論基礎(chǔ)。(1)根據(jù)位移協(xié)調(diào)條件,建立承壓完整井抽水引起地面沉降計算模型。以單層承壓含水層抽水為例,不考慮上覆土層固結(jié),地面最大水平位移與最大豎向位移相比,約小一個數(shù)量級,但其影響范圍與豎向位移相當(dāng)。含水層差異沉降顯著時,上覆土層的存在使得地面沉降值小于含水層壓縮量。差異沉降不顯著時,二者基本一致;考慮上覆土層固結(jié)過程,假設(shè)上覆土層飽和度不變,土體分別采取彈性及Merchant粘彈性本構(gòu)關(guān)系,固結(jié)初期,二者計算固結(jié)度大致相等,隨著固結(jié)時間增加,土體本構(gòu)關(guān)系取彈性時固結(jié)度大于取粘彈性時的固結(jié)度,二者計算固結(jié)度差值逐漸增大,按本文計算參數(shù),最大差值達29.6%。(2)通過調(diào)整樁長、建筑間距、降深和抽水層次,對建筑荷載、抽水以及二者共同作用引起的地面沉降進行數(shù)值模擬。樁長增加,建筑物沉降量值降低,但沉降分布幾乎不變;建筑間距增加,建筑物所處位置土體沉降最大,區(qū)域中心沉降隨建筑物間距增加沉降量值迅速降低;降深相同,開采深部含水層引起的沉降遠小于開采淺部含水層引起的沉降;抽水階段,建筑物影響范圍約為建筑物所處位置及附近0.5倍基礎(chǔ)寬度。開采第一含水層,建筑物的存在降低了地面沉降,建筑物所在位置沉降減少約50%;降深每增加1m,角樁樁頂軸力約增加1%,中心位置樁頂軸力約增加1.5%,樁身軸力變化幅度大,建筑物對土體變形影響顯著。開采第二含水層,建筑物對土體變形影響很小。樁基礎(chǔ)受力狀態(tài)的變化是建筑物及附近土體在抽水階段沉降分布發(fā)生變化的主要原因。根據(jù)建筑物及抽水沿深度影響范圍,結(jié)合上海中心城區(qū)地下水開采策略和分層沉降數(shù)據(jù),上海中心城區(qū)地面沉降主要原因已逐漸由開采地下水轉(zhuǎn)變?yōu)楣こ探ㄔO(shè),工程建設(shè)引起的地面沉降約占地面總沉降的40%。(3)地面沉降模型試驗。采用顆粒圖像測速技術(shù),研究建筑荷載和地下水開采引起土體分層變形規(guī)律。先建建筑使得后建建筑處土體發(fā)生固結(jié),后建建筑累計沉降小于先建建筑沉降。后建建筑使得原有建筑附近地面沉降速率增加,建筑荷載引起的地面沉降存在疊加效應(yīng);建筑物內(nèi)部區(qū)域因疊加效應(yīng)的存在,沉降量增加。建筑物外圍則沉降差較大;抽水時,建筑物樁基礎(chǔ)的負摩擦作用降低了建筑物及建筑物周圍土體的沉降,相應(yīng)地增加了建筑物周圍的差異沉降;相對于加載引起的沉降,抽水引起的沉降發(fā)展較為緩慢,但持續(xù)時間長。加載和抽取地下水引起的地面沉降,都是軟土層的變形占整個地面沉降的比例很大;地下水回灌抑制地面沉降效果顯著,但引起地面回彈量值甚微,地面沉降幾乎是不可逆的。(4)對比室內(nèi)模型試驗與數(shù)值模擬結(jié)果。高層建筑荷載引起的地面沉降,建筑范圍內(nèi)部因疊加效應(yīng)存在,沉降量值增加,但差異沉降相對降低。在已有建筑物的影響下,抽水引起的地面沉降,因樁土間相互作用,建筑物附近沉降值降低,但差異沉降增加。在建筑加載階段因疊加效應(yīng)沉降值增加、沉降差值相對降低的地區(qū),在抽水階段受建筑物影響依然較大,但沉降差值增加,沉降值相對降低;建筑荷載及抽水共同作用,使得建筑物附近沉降差變小,沉降趨于平緩。但若抽水量過大,則會引起沉降差反向增加。
[Abstract]:Land subsidence has caused enormous economic losses to more than 60 countries and regions in the world. Shanghai alone is as high as 29 billion yuan, with an average economic loss of about 153 million yuan per mm of decline. The study of ground subsidence caused by combined action of floor building load and groundwater level variation provides theoretical basis for prevention and control of ground subsidence in soft soil area. (1) According to displacement coordination conditions, a calculation model of ground subsidence caused by pumping of confined well is established. Taking pumping of single confined aquifer as an example, the ground is the largest without considering the consolidation of overlying soil layer. Compared with the maximum vertical displacement, the horizontal displacement is about one order of magnitude smaller, but its influence range is equivalent to the vertical displacement. When the differential settlement of the aquifer is significant, the ground settlement value of the overlying soil is smaller than the compression of the aquifer. When the differential settlement is not significant, the two are basically identical; considering the consolidation process of the overlying soil, the overlying soil is assumed to be saturated. At the initial stage of consolidation, the degree of consolidation calculated by the two methods is approximately equal. With the increase of consolidation time, the degree of consolidation calculated by the elastic constitutive relation is greater than that calculated by the viscoelastic constitutive relation, and the difference between the two methods increases gradually. According to the calculated parameters, the maximum difference is 29.6%. (2) By adjusting the pile length, building spacing, depth reduction and pumping level, the numerical simulation of the ground settlement caused by building load, pumping and their interaction is carried out. The settlement value decreases rapidly with the increase of spacing; the settlement caused by mining deep aquifer is much smaller than that caused by mining shallow aquifer; the influence range of buildings is about 0.5 times the width of foundation nearby and the location of buildings in pumping stage. The axial force on the top of the corner pile increases by 1%, and the axial force on the top of the pile increases by 1.5% with the increase of the depth by 1 m. According to the influence range of buildings and pumping along the depth, combined with the groundwater exploitation strategy and stratified subsidence data in the central area of Shanghai, the main cause of land subsidence in the central area of Shanghai has gradually changed from groundwater exploitation to engineering construction, and the land subsidence caused by engineering construction covers about land. (3) Land subsidence model test. Using particle image velocimetry technique, the soil layered deformation caused by building load and groundwater mining is studied. The soil consolidation occurs at the post-construction site and the accumulated settlement of the post-construction site is less than that of the pre-construction site. With the increase of building load, the ground subsidence caused by building load has superposition effect; the subsidence of building interior area increases because of superposition effect; the settlement difference of building exterior is larger; when pumping, the negative friction of building pile foundation reduces the subsidence of building and the soil around the building, and correspondingly increases the differential settlement around the building. Comparing with the settlement caused by loading, the subsidence caused by pumping develops slowly, but lasts for a long time. The subsidence caused by loading and pumping groundwater accounts for a large proportion of the total land subsidence. The effect of groundwater recharge on restraining land subsidence is remarkable, but the amount of ground rebound is very small, and the land subsidence is almost the same. (4) Comparing the results of indoor model test and numerical simulation, the ground subsidence caused by high-rise building load exists in the building area because of superposition effect, and the settlement value increases, but the differential settlement decreases relatively. In the area where the value of settlement increases due to superposition effect and the value of settlement difference decreases relatively, the value of settlement difference decreases relatively with the increase of the value of the building in the pumping stage, but the value of settlement difference decreases relatively with the increase of the value of the building in the pumping stage. However, if the pumping volume is too large, the differential settlement will increase.
【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】：P642.26
本文編號：2225792
[Abstract]:Land subsidence has caused enormous economic losses to more than 60 countries and regions in the world. Shanghai alone is as high as 29 billion yuan, with an average economic loss of about 153 million yuan per mm of decline. The study of ground subsidence caused by combined action of floor building load and groundwater level variation provides theoretical basis for prevention and control of ground subsidence in soft soil area. (1) According to displacement coordination conditions, a calculation model of ground subsidence caused by pumping of confined well is established. Taking pumping of single confined aquifer as an example, the ground is the largest without considering the consolidation of overlying soil layer. Compared with the maximum vertical displacement, the horizontal displacement is about one order of magnitude smaller, but its influence range is equivalent to the vertical displacement. When the differential settlement of the aquifer is significant, the ground settlement value of the overlying soil is smaller than the compression of the aquifer. When the differential settlement is not significant, the two are basically identical; considering the consolidation process of the overlying soil, the overlying soil is assumed to be saturated. At the initial stage of consolidation, the degree of consolidation calculated by the two methods is approximately equal. With the increase of consolidation time, the degree of consolidation calculated by the elastic constitutive relation is greater than that calculated by the viscoelastic constitutive relation, and the difference between the two methods increases gradually. According to the calculated parameters, the maximum difference is 29.6%. (2) By adjusting the pile length, building spacing, depth reduction and pumping level, the numerical simulation of the ground settlement caused by building load, pumping and their interaction is carried out. The settlement value decreases rapidly with the increase of spacing; the settlement caused by mining deep aquifer is much smaller than that caused by mining shallow aquifer; the influence range of buildings is about 0.5 times the width of foundation nearby and the location of buildings in pumping stage. The axial force on the top of the corner pile increases by 1%, and the axial force on the top of the pile increases by 1.5% with the increase of the depth by 1 m. According to the influence range of buildings and pumping along the depth, combined with the groundwater exploitation strategy and stratified subsidence data in the central area of Shanghai, the main cause of land subsidence in the central area of Shanghai has gradually changed from groundwater exploitation to engineering construction, and the land subsidence caused by engineering construction covers about land. (3) Land subsidence model test. Using particle image velocimetry technique, the soil layered deformation caused by building load and groundwater mining is studied. The soil consolidation occurs at the post-construction site and the accumulated settlement of the post-construction site is less than that of the pre-construction site. With the increase of building load, the ground subsidence caused by building load has superposition effect; the subsidence of building interior area increases because of superposition effect; the settlement difference of building exterior is larger; when pumping, the negative friction of building pile foundation reduces the subsidence of building and the soil around the building, and correspondingly increases the differential settlement around the building. Comparing with the settlement caused by loading, the subsidence caused by pumping develops slowly, but lasts for a long time. The subsidence caused by loading and pumping groundwater accounts for a large proportion of the total land subsidence. The effect of groundwater recharge on restraining land subsidence is remarkable, but the amount of ground rebound is very small, and the land subsidence is almost the same. (4) Comparing the results of indoor model test and numerical simulation, the ground subsidence caused by high-rise building load exists in the building area because of superposition effect, and the settlement value increases, but the differential settlement decreases relatively. In the area where the value of settlement increases due to superposition effect and the value of settlement difference decreases relatively, the value of settlement difference decreases relatively with the increase of the value of the building in the pumping stage, but the value of settlement difference decreases relatively with the increase of the value of the building in the pumping stage. However, if the pumping volume is too large, the differential settlement will increase.
【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】：P642.26
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