【摘要】：近年來,我國的基礎(chǔ)建設(shè)發(fā)展迅猛,其中水利、公路、鐵路、機場、港口以及碼頭等基礎(chǔ)設(shè)施正在如火如荼的建設(shè)。建設(shè)這些基礎(chǔ)設(shè)施時,其地基的極限承載力問題應(yīng)該首先考慮。目前現(xiàn)有的地基極限承載力計算方法多為半經(jīng)驗公式,且只針對均質(zhì)土地基。在工程中的地基多為復(fù)雜的層狀土地基,現(xiàn)有的層狀土地基極限承載力的計算方法尚未形成完善的理論體系。本文首先針對目前層狀土地基極限承載力計算缺乏準確的計算方法的問題,應(yīng)用上限解法,建立基于一般滑裂面的層狀土地基極限承載力的數(shù)值模擬方法;引入單純形法并結(jié)合隨機搜索法確定臨界滑動模式及最小加載系數(shù),求解極限承載力;并基于Excel內(nèi)嵌的VBA語言編寫地基極限承載力的計算程序以實現(xiàn)較為復(fù)雜函數(shù)的計算和計算的自動化;通過與現(xiàn)場試驗的對比分析證明了本方法及程序的準確性。計算結(jié)果與試驗結(jié)果表明:對于均質(zhì)土情況，，Vesic方法與本文方法的計算誤差最小,誤差不足1%, 而Meyerhof以及Terzaghi的方法與上限解的誤差最大,均超過20%;對于層狀土情況,本文方法與實驗結(jié)果接近,邁耶霍夫漢納理論和擴散角法的計算結(jié)果與上限解法的計算結(jié)果基本吻合,但擴散角法的計算結(jié)果更為接近上限解法的計算結(jié)果。而利用漢森加權(quán)平均公式得出的計算結(jié)果與上限解比較相差較大。本文還探討了應(yīng)用強度安全系數(shù)法對地基進行穩(wěn)定分析時，安全系數(shù)的取值標準。通過工程結(jié)構(gòu)風險分析和可靠度設(shè)計方法對上述問題進行解答,計算結(jié)果表明其允許安全系數(shù)(1.35)應(yīng)略大于邊坡等同類建筑物的相應(yīng)值。作者將可靠度理論應(yīng)用于目標可靠度指標為3.7和允許安全系數(shù)為1.35的一個典型地基算例,在土的凝聚力和摩擦系數(shù)變異系數(shù)分別為0.2和0.1的條件下,獲得土的凝聚力、摩擦系數(shù)的分項系數(shù)的值標定值分別為c=1.041, γf=1.418,與國外規(guī)范相近。應(yīng)用陳祖煜等提出的相對安全率判據(jù),可以發(fā)現(xiàn)上述的分項系數(shù)標定值通過了普適性考核。
[Abstract]:In recent years, the infrastructure of our country is developing rapidly, such as water conservancy, highway, railway, airport, port and wharf. When building these infrastructures, the ultimate bearing capacity of the foundation should be considered first. At present, most of the existing ultimate bearing capacity calculation methods are semi-empirical formula, and only for homogeneous soil foundation. Most of the foundations in engineering are complex layered soil foundations, and the existing calculation methods of ultimate bearing capacity of layered soil foundations have not yet formed a perfect theoretical system. In this paper, aiming at the lack of accurate calculation method for the ultimate bearing capacity of layered soil foundation at present, a numerical simulation method of ultimate bearing capacity of layered soil foundation based on general sliding surface is established by using the upper limit solution. The simplex method and random search method are introduced to determine the critical sliding mode and the minimum loading coefficient to solve the ultimate bearing capacity. The calculation program of the ultimate bearing capacity of foundation is compiled based on the VBA language embedded in Excel to realize the calculation and automation of the complex function, and the accuracy of the method and program is proved by comparing with the field test. The results of calculation and experiment show that for homogeneous soil, the calculation error between Vesic method and this method is the smallest, and the error is less than 1, while the error between Meyerhof and Terzaghi method and upper bound solution is the biggest, both exceeding 20 parts. In the case of layered soil, the present method is close to the experimental results. The results of Meyerhoff Hanna theory and diffusion angle method are in good agreement with those of the upper bound method, but the results of diffusion angle method are closer to those of the upper bound method. However, the calculation results obtained by using Hansen's weighted average formula are quite different from the upper bound solutions. This paper also discusses the criterion of safety factor when using the method of strength safety factor to analyze the stability of foundation. By means of engineering structural risk analysis and reliability design method, the results show that the allowable safety factor (1.35) should be slightly larger than the corresponding value of similar buildings such as slope. The reliability theory is applied to a typical foundation with a target reliability index of 3.7 and a allowable safety factor of 1.35. The coefficient of variation of cohesion and friction coefficient is 0.2 and 0.1, respectively. The values of cohesion and friction coefficient of soil are determined to be c _ (1.041) and 緯 _ f _ (1.418) respectively, which are close to those of foreign specifications. By applying the criterion of relative safety rate proposed by Chen Zuyu et al, it can be found that the calibration values of the above sub-coefficients have passed the universal assessment.
【學位授予單位】：西安理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU470

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