本文選題：基坑支護 + 基坑監(jiān)測��； 參考：《湖南科技大學(xué)》2017年碩士論文

【摘要】：基坑工程是集巖土工程和結(jié)構(gòu)工程等多學(xué)科于一體的系統(tǒng)工程,綜合性強,影響因素多。在基坑開挖過程中,原有土體穩(wěn)定狀態(tài)將被打破,出現(xiàn)側(cè)面臨空的狀態(tài),發(fā)生應(yīng)力重分布,導(dǎo)致土體出現(xiàn)不穩(wěn)定的現(xiàn)象,引發(fā)工程安全性問題。為保證施工安全,就需要進行支護工程,因此對于基坑開挖后土體與支護結(jié)構(gòu)之間的相互作用成了設(shè)計過程中人們最關(guān)心的問題。深圳富森基坑工程位于光明新區(qū)龍大高速東側(cè),華夏二路南側(cè)。場地內(nèi)自上而下地層大體可分為五大層,即人工填土層(Q4ml)、湖積層(Q4l)、沖洪積層(Q3al+pl)和殘積層(Qel),下伏基巖為震旦系混合巖(Z)。基坑支護采用復(fù)合土釘墻設(shè)計,分別采用放坡加土釘加微型樁加錨索,土釘錨索加微型樁,以及樁錨支護的支護形式�，F(xiàn)場監(jiān)測工作中共設(shè)置14個水平、垂直位移觀測點,監(jiān)測施工過程中基坑壁上產(chǎn)生的水平、垂直位移。并設(shè)置了4個水位觀測點,觀測基坑止水帷幕滲漏問題。最終得到的監(jiān)測結(jié)果可以發(fā)現(xiàn)最大位移在基坑壁中部,水平位移最大達到25mm,垂直位移最大達到21mm,證明了該基坑施工過程的安全性。本文通過FLAC3D軟件的數(shù)值模擬,建立了富森基坑三維模型,分析基坑開挖支護前后應(yīng)力應(yīng)變情況。支護前后對比發(fā)現(xiàn),最大、最小主應(yīng)力較大程度的減小,在進行支護后,最大、最小主應(yīng)力最大值區(qū)域整體范圍向著支護樁體靠近。在基坑底靠近坡腳的位置,最大、最小主應(yīng)力值相對偏大,存在應(yīng)力集中現(xiàn)象,從而引起在基坑底部土體水平位移值偏大,說明這個部位受力狀況比較復(fù)雜,導(dǎo)致基坑底部支護樁位置有較大的剪應(yīng)變產(chǎn)生;并可以發(fā)現(xiàn)基坑尺寸對最大主應(yīng)力分布有一定的影響�；铀轿灰谱畲笾导性谥猩喜�,并且方向向著基坑內(nèi)部。進行支護后由于支護結(jié)構(gòu)的支撐使得沉降最大位置不在基坑坡頂開挖邊線處,其墻后沉降整體分布形式類似勺狀,基坑沉降最大值發(fā)生在基坑坡頂距離開挖邊線5.0~8.0m的位置。放坡支護在開挖到一定深度之前對應(yīng)力有緩解作用;在基坑坡腳存在著應(yīng)力集中現(xiàn)象,使得基坑坡腳位置水平位移相對較大;在基坑開挖到一定程度后,基坑開挖尺寸開始對基坑應(yīng)力應(yīng)變起重要作用。本文通過FLAC3D軟件的有限差分法得到的相關(guān)結(jié)論可以為類似工程設(shè)計施工提供一定的借鑒。
[Abstract]:Foundation pit engineering is a systematic engineering with many disciplines such as geotechnical engineering and structural engineering. During the excavation of foundation pit, the stable state of the original soil will be broken, and the condition of side face will appear, and the stress redistribution will occur, which will lead to the unstable phenomenon of soil mass and cause the engineering safety problem. In order to ensure the safety of construction, it is necessary to carry out support engineering, so the interaction between soil and supporting structure after excavation has become the most concerned problem in the design process. Shenzhen Fusen Foundation Pit Project is located in the east of Longda Expressway, Guangming New area, and south of Huaxia Road 2. The upper and lower strata in the site can be divided into five layers, I. E. artificial filling soil layer (Q4ml), lacustrine layer (Q4l), alluvial layer (Q3alpl) and residual layer (Qel), and the lower voluminous rock is Sinian migmatite (Z). The composite soil nailing wall is used to support the foundation pit, and the supporting forms of the pile and anchor support are adopted, respectively, such as slope placement plus soil nailing plus micro pile plus anchor cable, soil nail anchor cable plus micro pile, as well as the support form of pile anchor support. A total of 14 horizontal and vertical displacement observation points were set up in the field monitoring work to monitor the horizontal and vertical displacement in the foundation pit wall during the construction process. At the same time, four water level observation points were set up to observe the leakage of water stop curtain in foundation pit. The monitoring results show that the maximum displacement is 25 mm for horizontal displacement and 21 mm for vertical displacement in the middle of the foundation pit wall, which proves the safety of the foundation pit construction process. In this paper, through numerical simulation of FLAC3D software, a three-dimensional model of Fucson foundation pit is established, and the stress-strain situation before and after excavation is analyzed. Before and after supporting, it is found that the maximum and minimum principal stresses decrease to a large extent, and after supporting, the maximum and minimum principal stresses of the whole region are close to the supporting pile body. At the bottom of the foundation pit near the foot of the slope, the maximum and minimum principal stress values are relatively large, and there exists the phenomenon of stress concentration, which causes the horizontal displacement of the soil at the bottom of the foundation pit to be larger, which indicates that the stress condition of this part is relatively complex. It can be found that the size of foundation pit has a certain influence on the distribution of maximum principal stress. The maximum horizontal displacement of foundation pit is concentrated in the middle and upper part, and the direction is toward the inside of foundation pit. After supporting, the maximum position of settlement is not located at the edge line of the slope top of foundation pit, and the overall distribution of settlement behind the wall is similar to that of ladle. The maximum settlement of foundation pit occurs at the position of 5.0 ~ 8.0 m from the slope top of foundation pit to the edge line of excavation. Slope support can alleviate stress before excavation to a certain depth; stress concentration phenomenon exists at the foot of foundation pit, which makes the horizontal displacement of foundation pit slope foot relatively large; after excavation to a certain extent, The excavation size of foundation pit plays an important role in the stress and strain of foundation pit. The conclusions obtained by finite difference method of FLAC3D software can be used for reference in the design and construction of similar projects.
【學(xué)位授予單位】：湖南科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU433

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