本文關(guān)鍵詞：填海造陸地區(qū)深大基坑變形時空效應(yīng)及其控制研究　出處：《重慶大學(xué)》2015年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 軟土蠕變 深基坑 時空效應(yīng) 數(shù)值模擬 FLAC~(3D)二次開發(fā)

【摘要】：隨著我國城市化進程快速的發(fā)展,不斷擴張的城市建設(shè)與有限的土地資源之間的矛盾日益凸顯,因此,填海造陸成為沿海城市增加土地資源儲備、擴展城市空間的重要途徑。如今伴隨各種高層、超高層建筑的建設(shè),各種超大、超深和復(fù)雜的基坑工程在填海造陸地區(qū)的場地上應(yīng)運而生,然而,填海造陸層下臥深厚的海相沉積軟土在基坑開挖過程中容易產(chǎn)生蠕變變形,使基坑支護結(jié)構(gòu)及周圍土體的變形具有明顯的時空效應(yīng),為了基坑的安全施工,需要對時空變形進行嚴格地控制。填海造陸層下臥的海相沉積軟土的蠕變力學(xué)特性是影響整個基坑時空變形的重要因素,鑒于此,論文基于前人對軟土蠕變的研究,綜合采用室內(nèi)試驗、理論分析、數(shù)值模擬等手段,對下臥海相沉積軟土的蠕變力學(xué)特性和本構(gòu)模型展開研究,并將研究成果應(yīng)用到填海造陸地區(qū)深大基坑變形時空效應(yīng)及其控制的工程實踐中。論文的研究內(nèi)容和成果如下:①對基坑海相沉積軟土的基本物理性質(zhì)和礦物成分進行系統(tǒng)的研究,揭示了高親水礦物含量、高細粒含量和高粘粒含量是造成海相沉積軟土非線性蠕變的重要原因。采用應(yīng)力控制式三軸儀,對不同深度處的海相沉積軟土展開相應(yīng)圍壓下的固結(jié)不排水蠕變試驗,獲得該軟土的蠕變特性認識�；谠囼灲Y(jié)果,重點分析海相沉積軟土在低于屈服應(yīng)力和高于屈服應(yīng)力時各自的蠕變特性,以及蠕變特性隨時間的變化規(guī)律,通過擬合得到孔隙水壓隨蠕變時間和應(yīng)力水平的函數(shù)關(guān)系式。②分析基坑海相沉積軟土的線性粘彈性蠕變和非線性粘塑性蠕變的規(guī)律,采用標(biāo)準(zhǔn)線性體描述粘彈性蠕變、標(biāo)準(zhǔn)線性體與經(jīng)驗公式相結(jié)合來描述粘塑性蠕變,建立以元件模型和經(jīng)驗?zāi)Ｐ蜑榻M合體的海相沉積軟土的蠕變本構(gòu)模型。采用基于經(jīng)典擬牛頓BFGS算法的MATLAB程序,對軟土蠕變本構(gòu)模型的參數(shù)進行辨識,獲得較高精度的模型參數(shù),能夠很好地描述不同深度處海相沉積軟土的蠕變特性。③基于有限差分理論推導(dǎo)海相沉積軟土應(yīng)力場控制和滲透場控制的差分方程;利用Microsoft Visual C++6.0軟件獲得該軟土蠕變本構(gòu)模型的數(shù)值實現(xiàn)程序Szsoftsoilmodel.dll。根據(jù)該數(shù)值實現(xiàn)程序得到圍壓為100kPa、200kPa和250kPa時的蠕變數(shù)值計算結(jié)果,通過數(shù)值計算結(jié)果和蠕變試驗結(jié)果的對比,驗證了數(shù)值實現(xiàn)程序的正確性,為基坑海相沉積軟土蠕變模型的工程應(yīng)用奠定了基礎(chǔ)。④根據(jù)實際起伏不定的地層建立深大基坑的三維模型,分別利用軟土蠕變模型和Mohr-Coulomb模型對支護樁的水平位移進行數(shù)值計算。對比數(shù)值計算結(jié)果和現(xiàn)場監(jiān)測數(shù)據(jù),結(jié)果表明:考慮軟土蠕變模型的樁身水平位移比Mohr-Coulomb模型的計算結(jié)果更加符合實際的樁身水平位移,驗證軟土蠕變模型的數(shù)值實現(xiàn)程序用于基坑變形數(shù)值分析的合理性。⑤將海相沉積軟土的蠕變本構(gòu)模型應(yīng)用到填海造陸地區(qū)深大基坑變形時空效應(yīng)的研究中,重點分析了支護樁樁身水平位移、基坑周圍地面沉降、坑底隆起、樁身彎矩、樁身剪力和錨索預(yù)應(yīng)力損失的空間特性和時間特性�？紤]軟土蠕變本構(gòu)模型的數(shù)值分析表明:首先,基坑變形和受力的時空表現(xiàn)不是簡單的在基坑拐角處弱,在基坑對稱中心處強,具體變形和受力的時空表現(xiàn)與局部軟土的厚度、蠕變強弱和開挖順序等因素有關(guān);其次,基坑?xùn)|側(cè)因靠近河流,其樁身水平位移和周圍地面沉降在基坑各側(cè)中是最大的,因此基坑?xùn)|側(cè)是整個基坑變形控制的重點區(qū)域;最后,對比前人在基坑建模時地層為水平的情況,根據(jù)彎曲地層所建立的基坑模型能夠更好地反映基坑的實際變形性狀。⑥以基坑?xùn)|側(cè)y=135m處的變形控制為例,在綜合分析基坑變形和環(huán)境保護的影響因素的基礎(chǔ)上,提出多種控制方法組合而成的三種變形控制方案�？紤]海相沉積軟土蠕變,對以上三種變形控制方案的優(yōu)劣性進行數(shù)值驗證。確定了擴大頭預(yù)應(yīng)力錨索+坑外主動區(qū)注漿是最優(yōu)的變形控制方案,為填海造陸地區(qū)深大基坑的變形控制提供指導(dǎo)。
[Abstract]:With the development of China's city development rapidly, the contradiction between the continuous expansion of the city construction and the limited land resources has become increasingly prominent, therefore, become the coastal city of sea reclamation to increase land reserves, an important way to expand the city space. Now with a variety of high-rise building, high-rise building, a variety of large, complex and super deep foundation pit in the reclamation area of the site came into being, however, the sea reclamation layer under deep marine soft soil is prone to creep deformation in the excavation process, the deformation of supporting structure of foundation pit and the surrounding soil has obvious temporal and spatial effects, in order to safety construction, need to strictly control the deformation time land reclamation. The creep mechanical properties of layer under the marine soft soil is an important factor affecting the deformation of foundation pit, time and space in view of this, based on the predecessors of the Study on creep of soft soil, using a combination of laboratory test, theoretical analysis, numerical simulation, creep mechanical properties of underlying marine soft soil and its constitutive model is studied, and the results are applied to the engineering practice of land reclamation and control area of time-space effect of deep foundation pit deformation. The main research contents and achievements as follows: the systematic research on the foundation of the basic physical properties of marine soft soil and mineral composition, reveals high hydrophilic mineral content, high fines content and high clay content is an important cause of marine soft soil nonlinear creep. The stress controlled three axis instrument, marine soft soil of different depths. At the start of the corresponding consolidation confining pressure under undrained creep test, the creep properties of soft soil to obtain knowledge. Based on the experimental results, focuses on the analysis of marine soft soil in the lower yield stress and higher The yield stress creep characteristics respectively, and the variation of creep properties with time, obtained by the fitting of pore water pressure with the creep time and should function between stress level. The analysis of marine soft soil foundation of linear viscoelastic creep and nonlinear viscoplastic creep law, using the standard linear viscoelastic body description creep, standard linear model and empirical formula were combined to describe the viscoplastic creep, creep to establish element model and empirical model for marine sedimentary soft soil combination constitutive model. Using the classical quasi Newton BFGS algorithm based on MATLAB program, the parameters of soft soil creep constitutive model identification, model parameters high precision, can well describe the creep characteristics at different depths of the marine sedimentary soft soil. Based on the finite difference theory of marine soft soil stress field and seepage field difference control Differential equation; Szsoftsoilmodel.dll. program according to the numerical implementation procedures are confining pressure for 100kPa to achieve the values of creep constitutive model using Microsoft Visual C++6.0 software, the calculation results of creep numerical 200kPa and 250kPa, by comparing the numerical results and the creep test results, verify the correctness of the numerical implementation of the program, which the basis of the engineering application foundation for marine sedimentary soft soil creep model. Establishing the three-dimensional model of deep foundation pit according to the actual fluctuating strata, respectively using the soft soil creep model and Mohr-Coulomb model were used to calculate the horizontal displacement of the retaining pile. The calculation results and monitoring data, the numerical results show that considering the horizontal displacement of the pile of soft soil creep model is better than the Mohr-Coulomb model calculation results of horizontal displacement of the pile is more consistent with the actual verification, the soft soil creep model The numerical implementation procedure for the rationality of foundation pit deformation numerical analysis. The creep of marine soft soil constitutive model is applied to the research on the land reclamation area of the time-space effect of deep foundation pit deformation, analyzes the supporting pile foundation pit horizontal displacement, ground settlement, heave, pile bending moment, the characteristic of space and time the characteristics of pile shear and prestress loss. The numerical analysis shows that the constitutive model of soft soil creep considerations: first, the performance of time and space of foundation pit deformation and stress is not a simple corner in the pit in the center of symmetry at the foundation is weak, strong, specific deformation and stress of the local space performance and thickness of the soft soil, the the creep strength factor and excavation sequence; secondly, the foundation pit near the river, the pile displacement and ground settlement in the foundation pit is the largest, so the East is the whole foundation pit The deformation control in key areas; finally, compared with the previous model in foundation pit formation level, according to the actual deformation of foundation pit formation the bending model can better reflect the foundation. According to control deformation of foundation pit at the east side of y=135m as an example, based on a comprehensive analysis of the influence of foundation pit deformation and environmental factors on and put forward three kinds of deformation control scheme and a combination of various control methods. Considering the marine soft soil creep, numerical verification of the above three kinds of deformation control schemes. The enlarged grouting prestressed anchor cable and pit deformation control scheme of active area is optimal, provide guidance for the deformation control of the sea reclamation area deep pit.

【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TU753

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