【摘要】：在地下水位較高的地區(qū)進(jìn)行深基坑施工時(shí),必須在開(kāi)挖之前進(jìn)行降水,控制地下水位便于施工并保證基坑的穩(wěn)定性。降低地下水位從而減少基坑內(nèi)外水頭差是比較常用、有效且經(jīng)濟(jì)的措施,但其也會(huì)對(duì)周圍環(huán)境造成不良影響,如引起地表不均勻沉降、圍護(hù)結(jié)構(gòu)變形等。本論文結(jié)合某基坑開(kāi)挖降水實(shí)例,分析滲流對(duì)基坑外地表沉降及圍護(hù)結(jié)構(gòu)影響。 首先簡(jiǎn)要介紹了目前基坑工程的發(fā)展現(xiàn)狀,指出基坑降水存在的問(wèn)題、常用降水方法及適用范圍。 通過(guò)Midas Gts軟件進(jìn)行有限元模擬,使建立的模型正確反映基坑開(kāi)挖降水過(guò)程。隨著基坑開(kāi)挖深度的增加,支護(hù)結(jié)構(gòu)變形逐漸增大,并且最大變形位置發(fā)生在開(kāi)挖面附近；基坑的沉降變形隨著開(kāi)挖深度增加而增大,最大沉降位置發(fā)生在16m位置(即一倍開(kāi)挖深度)：在此基礎(chǔ)上,研究考慮滲流與不考慮滲流狀態(tài)下對(duì)基坑開(kāi)挖的影響。 其次對(duì)不同開(kāi)挖階段下的孔隙水壓力、流速等值線進(jìn)行了研究。離地下連續(xù)墻近的孔隙水壓值變化最大,離地下連續(xù)墻越遠(yuǎn),降水開(kāi)挖對(duì)孔隙水壓變化影響越�。婚_(kāi)挖面墻體附近的流速等值線分布較密,墻體下端地下水在此處有較高的流速；而離墻體越遠(yuǎn)的地方,流速等值線分布越來(lái)越稀疏。 最后研究基坑開(kāi)挖不同影響因素,分別從土體的滲透系數(shù)和基坑內(nèi)的水位變化情況進(jìn)行分析。得出同時(shí)改變x、y、z方向滲透系數(shù),對(duì)圍護(hù)結(jié)構(gòu)、坑外地表沉降及基坑隆起z方向影響遠(yuǎn)大于xy平面方向的影響：隨著基坑內(nèi)部水位增加,基坑外地表沉降逐漸減少同時(shí),支護(hù)結(jié)構(gòu)水平位移隨之減少,并隨著水位增加發(fā)生最大水平位移位置逐漸向上移動(dòng)趨勢(shì),同時(shí)抑制基坑底部隆起。
[Abstract]:In the construction of deep foundation pit in areas with high groundwater level, dewatering must be carried out before excavation, and the control of groundwater level is convenient for construction and the stability of foundation pit must be guaranteed. It is common, effective and economical to reduce the water head difference between inside and outside of the foundation pit by lowering the groundwater level, but it will also cause adverse effects on the surrounding environment, such as uneven settlement of the ground surface, deformation of the enclosure structure, and so on. In this paper, the influence of seepage flow on the surface settlement and enclosure structure of foundation pit is analyzed with an example of foundation pit excavation dewatering. Firstly, this paper briefly introduces the development of foundation pit engineering, points out the existing problems of foundation pit dewatering, commonly used dewatering methods and its applicable scope. The finite element simulation is carried out by Midas Gts software to make the model accurately reflect the dewatering process of foundation pit excavation. With the increase of excavation depth, the deformation of supporting structure increases gradually, and the maximum deformation occurs near the excavation surface. The settlement deformation of foundation pit increases with the increase of excavation depth, and the maximum settlement occurs in 16m position (that is, double excavation depth). On this basis, the influence of seepage and non-seepage on excavation of foundation pit is studied. Secondly, the pore water pressure and velocity contour at different excavation stages are studied. The variation of pore water pressure near underground continuous wall is the biggest, and the farther away from underground continuous wall, the less influence of precipitation excavation on pore water pressure change. The distribution of velocity isoline near the wall of excavated surface is relatively dense, and the groundwater at the lower end of the wall has a higher velocity here, and the farther away from the wall, the distribution of velocity isoline becomes more and more sparse. Finally, the factors influencing the excavation of foundation pit are studied, and the seepage coefficient of soil and the variation of water level in the foundation pit are analyzed respectively. It is concluded that the influence of changing the permeability coefficient of xyyangz direction at the same time on the enclosure structure, pit surface settlement and pit uplift z direction is much greater than that of xy plane direction: with the increase of the water level inside the foundation pit, the external surface settlement of the foundation pit decreases gradually, at the same time, The horizontal displacement of the supporting structure decreases and the maximum horizontal displacement position moves upward with the increase of the water level and the uplift at the bottom of the foundation pit is restrained at the same time.
【學(xué)位授予單位】：海南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU46

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