軟土地區(qū)深基坑坑底抗隆起穩(wěn)定性分析
發(fā)布時(shí)間：2018-07-20 12:38
【摘要】：我國(guó)長(zhǎng)江流域及沿海地區(qū)多為軟土平原地區(qū),這些地區(qū)土質(zhì)承載力低、地下水位高,容易發(fā)生基坑失穩(wěn)事故,基坑隆起是基坑失穩(wěn)的常見(jiàn)形式之一。在深基坑工程安全評(píng)估中,深基坑坑底抗隆起破壞分析具有重要參考價(jià)值,同時(shí)也是基坑工程設(shè)計(jì)中的一項(xiàng)重要內(nèi)容。深基坑坑底抗隆起穩(wěn)定性分析方法主要有三種：極限平衡法、極限分析法和數(shù)值分析法。 本文以極限平衡法中的圓弧滑動(dòng)模式為理論基礎(chǔ),認(rèn)為現(xiàn)有圓弧滑動(dòng)簡(jiǎn)化公式應(yīng)考慮分層土的土體參數(shù)、擋墻參數(shù)以及加固土參數(shù)的影響,提出了考慮這三類影響因素的深基坑坑底抗隆起穩(wěn)定性安全系數(shù)計(jì)算公式,并通過(guò)力矩相等原則推導(dǎo)了等效土體參數(shù)的取值方法。同時(shí),分析了圓弧滑動(dòng)模式和極限承載力模式計(jì)算公式的適用條件。通過(guò)對(duì)工程實(shí)例的計(jì)算,驗(yàn)證了不同公式在不同條件下的適用性和準(zhǔn)確性。然后,對(duì)Prandtl極限承載力模式計(jì)算公式及圓弧滑動(dòng)模式公式,利用MATLAB進(jìn)行編程,把土體參數(shù)、擋墻參數(shù)以及加固土參數(shù)對(duì)深基坑坑底抗隆起穩(wěn)定性的影響程度進(jìn)行對(duì)比分析。最后,通過(guò)極限承載力模式結(jié)合Vesic理論,推導(dǎo)了存在軟弱下臥層深基坑坑底抗隆起穩(wěn)定安全系數(shù)計(jì)算公式,并提出了可以不考慮軟弱下臥層影響的臨界厚度概念,分析了不同參數(shù)影響下臨界厚度的大小。得到以下幾項(xiàng)主要研究成果： (1)本文推導(dǎo)公式與國(guó)家規(guī)范公式對(duì)比,考慮了基坑內(nèi)外主被動(dòng)土壓力系數(shù)的區(qū)別、加固土的影響以及擋墻提供彎矩的作用,并詳細(xì)推導(dǎo)了等效土體參數(shù)的取值方法。通過(guò)工程算例,分析對(duì)比了本文推導(dǎo)公式與其他公式計(jì)算結(jié)果的區(qū)別。當(dāng)擋墻底部以上土質(zhì)較差時(shí),本文推導(dǎo)公式比Prandtl極限承載力模式公式更加合理。 (2)在深基坑坑底抗隆起穩(wěn)定性各影響因素中,土體內(nèi)聚力、土體內(nèi)摩擦角及土體重度和擋墻插入比對(duì)深基坑坑底抗隆起穩(wěn)定性影響很大。通過(guò)計(jì)算分析對(duì)比,各參數(shù)影響程度從大到小排序?yàn)椋和馏w內(nèi)摩擦角,土體重度,土體內(nèi)聚力,擋墻插入比,加固土無(wú)側(cè)限抗壓強(qiáng)度,地面超載。 (3)在分析存在軟弱下臥層的基坑坑底抗隆起穩(wěn)定性時(shí),當(dāng)擋墻底部離軟弱下臥層頂部的厚度小于臨界厚度時(shí),需要考慮軟弱下臥層對(duì)基坑抗隆起穩(wěn)定性的影響；當(dāng)擋墻底部離軟弱下臥層頂部的厚度大于臨界厚度時(shí),可不考慮軟弱下臥層對(duì)基坑抗隆起穩(wěn)定性的影響。
[Abstract]:The Yangtze River Basin and the coastal area are mostly soft soil plain area. The soil bearing capacity is low and the groundwater level is high, the foundation pit instability is easy to occur. The foundation pit bulge is one of the common forms of the foundation pit instability. In the safety assessment of deep foundation pit engineering, the analysis of the foundation pit bottom anti uplift failure is of important reference value, and it is also a foundation pit. There are three main methods for analyzing the uplift stability of deep foundation pit bottom: limit equilibrium method, limit analysis method and numerical analysis method.
Based on the theory of circular arc sliding mode in the limit equilibrium method, this paper considers that the existing simplified formula of circular arc sliding should take into account the soil parameters of the layered soil, the parameters of the retaining wall and the influence of the reinforced soil parameters. The formula for calculating the safety factor of the stability of the bottom of the deep foundation pit with these three factors is considered, and the original moment is equal to the original moment. The method of obtaining the equivalent soil parameters is derived. At the same time, the applicable conditions for the calculation formula of the circular arc sliding mode and the ultimate bearing capacity model are analyzed. The applicability and accuracy of the different formulas under different conditions are verified by the calculation of the engineering examples. Then, the calculation formula of the Prandtl extreme limit bearing capacity model and the circular slip mode are given. The formula is programmed with MATLAB. The influence degree of soil parameters, retaining wall parameters and reinforcement parameters on the stability of deep foundation pit at the bottom of the pit is compared and analyzed. Finally, the calculation formula of stability safety factor for the foundation pit bottom of deep foundation pit with weak substratum is derived through the ultimate bearing capacity model and the Vesic theory. The critical thickness can be considered without consideration of the influence of soft substratum, and the critical thickness under the influence of different parameters is analyzed.
(1) the comparison between the derived formula and the national standard formula, the difference between the dynamic soil pressure coefficient of the main ground inside and outside of the foundation pit, the effect of reinforcement soil and the effect of the retaining wall providing bending moment, and the value method of the equivalent soil parameters are derived in detail. The difference between the derived formula and the calculation results of the other formulas is analyzed and compared by an engineering example. When the soil quality above the bottom of the retaining wall is poor, the formula deduced in this paper is more reasonable than the formula of Prandtl ultimate bearing capacity formula.
(2) among the factors affecting the stability of the deep foundation pit, the cohesive force, the friction angle of the soil and the gravity of the soil and the insertion of the retaining wall have a great influence on the stability of the bottom of the deep foundation pit. By the calculation and analysis, the degree of influence of the parameters from the large to small is the internal friction angle, the soil mass, the cohesive force of the soil and the retaining wall. The insertion ratio has no unconfined compressive strength of the reinforced soil, and the ground is overloaded.
(3) when analyzing the stability of foundation pit bottom in soft substratum, when the thickness of the bottom of the retaining wall is less than the critical thickness at the top of the weak substratum, it is necessary to consider the influence of the soft substratum on the stability of the foundation pit against the bulge. The effect of lying layer on the stability of foundation pit anti uplift.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU473.2
本文編號(hào)：2133538
[Abstract]:The Yangtze River Basin and the coastal area are mostly soft soil plain area. The soil bearing capacity is low and the groundwater level is high, the foundation pit instability is easy to occur. The foundation pit bulge is one of the common forms of the foundation pit instability. In the safety assessment of deep foundation pit engineering, the analysis of the foundation pit bottom anti uplift failure is of important reference value, and it is also a foundation pit. There are three main methods for analyzing the uplift stability of deep foundation pit bottom: limit equilibrium method, limit analysis method and numerical analysis method.
Based on the theory of circular arc sliding mode in the limit equilibrium method, this paper considers that the existing simplified formula of circular arc sliding should take into account the soil parameters of the layered soil, the parameters of the retaining wall and the influence of the reinforced soil parameters. The formula for calculating the safety factor of the stability of the bottom of the deep foundation pit with these three factors is considered, and the original moment is equal to the original moment. The method of obtaining the equivalent soil parameters is derived. At the same time, the applicable conditions for the calculation formula of the circular arc sliding mode and the ultimate bearing capacity model are analyzed. The applicability and accuracy of the different formulas under different conditions are verified by the calculation of the engineering examples. Then, the calculation formula of the Prandtl extreme limit bearing capacity model and the circular slip mode are given. The formula is programmed with MATLAB. The influence degree of soil parameters, retaining wall parameters and reinforcement parameters on the stability of deep foundation pit at the bottom of the pit is compared and analyzed. Finally, the calculation formula of stability safety factor for the foundation pit bottom of deep foundation pit with weak substratum is derived through the ultimate bearing capacity model and the Vesic theory. The critical thickness can be considered without consideration of the influence of soft substratum, and the critical thickness under the influence of different parameters is analyzed.
(1) the comparison between the derived formula and the national standard formula, the difference between the dynamic soil pressure coefficient of the main ground inside and outside of the foundation pit, the effect of reinforcement soil and the effect of the retaining wall providing bending moment, and the value method of the equivalent soil parameters are derived in detail. The difference between the derived formula and the calculation results of the other formulas is analyzed and compared by an engineering example. When the soil quality above the bottom of the retaining wall is poor, the formula deduced in this paper is more reasonable than the formula of Prandtl ultimate bearing capacity formula.
(2) among the factors affecting the stability of the deep foundation pit, the cohesive force, the friction angle of the soil and the gravity of the soil and the insertion of the retaining wall have a great influence on the stability of the bottom of the deep foundation pit. By the calculation and analysis, the degree of influence of the parameters from the large to small is the internal friction angle, the soil mass, the cohesive force of the soil and the retaining wall. The insertion ratio has no unconfined compressive strength of the reinforced soil, and the ground is overloaded.
(3) when analyzing the stability of foundation pit bottom in soft substratum, when the thickness of the bottom of the retaining wall is less than the critical thickness at the top of the weak substratum, it is necessary to consider the influence of the soft substratum on the stability of the foundation pit against the bulge. The effect of lying layer on the stability of foundation pit anti uplift.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU473.2
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