本文選題：濕陷性黃土 + 長短樁復(fù)合地基�。� 參考：《長安大學(xué)》2014年碩士論文

【摘要】：高速鐵路的正常運(yùn)營對(duì)路基沉降要求相當(dāng)嚴(yán)格，其中最關(guān)鍵的是控制地基沉降然而，長短樁復(fù)合地基技術(shù)在濕陷性黃土地區(qū)應(yīng)用后，不但控制了地基總沉降量，而且也取得了良好的經(jīng)濟(jì)效益和社會(huì)效益但是，前人對(duì)其理論研究還不夠深入和完善因此，本文依托濕陷性黃土地區(qū)在建的高速鐵路項(xiàng)目對(duì)長短樁復(fù)合地基的沉降進(jìn)行系統(tǒng)的研究本文研究內(nèi)容主要體現(xiàn)在以下幾個(gè)方面： 第一，分析長短樁復(fù)合地基在路堤荷載作用下的工作機(jī)理后，總結(jié)了長短樁復(fù)合地基承載力計(jì)算公式同時(shí)，概述了多種復(fù)合地基沉降計(jì)算方法，，并對(duì)其進(jìn)行了分析 第二，選取兩個(gè)典型的路基斷面，采用彈性土堤法Boussinesq三角形荷載法和Boussinesq組合荷載法計(jì)算得到地基附加應(yīng)力，然后通過復(fù)合模量法和弦線模量法分別計(jì)算長短樁復(fù)合地基的沉降值，并與實(shí)測(cè)沉降值比較，得到了適用于濕陷性黃土地區(qū)長短樁復(fù)合地基的沉降計(jì)算方法 第三，利用FLAC3D軟件對(duì)長短樁復(fù)合地基進(jìn)行數(shù)值模擬分析，樁間土采用Mohr-Coulomb模型，在數(shù)值計(jì)算過程中，最佳的深度取3.5b，最佳的寬度取4.5b，b為路基底寬度數(shù)值模擬結(jié)果表明，隨著墊層厚度墊層模量的增大，地基沉降量分別表現(xiàn)出增加和減��；隨著長樁長度和短樁樁端以上樁間土模量的增大，地基沉降量顯著減�。浑S著長樁模量和短樁長度模量的增大，地基沉降量減小不明顯 第四，根據(jù)兩個(gè)試驗(yàn)段路基沉降觀測(cè)資料，運(yùn)用雙曲線法拋物線法和BP神經(jīng)網(wǎng)絡(luò)進(jìn)行沉降預(yù)測(cè)其中，BP神經(jīng)網(wǎng)絡(luò)模型的構(gòu)建，樣本的訓(xùn)練以及預(yù)測(cè)借助MATLAB軟件來完成然后，計(jì)算并對(duì)比三種預(yù)測(cè)方法的擬合指標(biāo)r2和相對(duì)誤差，發(fā)現(xiàn)采用BP神經(jīng)網(wǎng)絡(luò)最適合預(yù)測(cè)濕陷性黃土地區(qū)長短樁復(fù)合地基的沉降，其擬合精度和預(yù)測(cè)精度都很高
[Abstract]:The normal operation of high-speed railway requires the subgrade settlement very strictly, among which the key is to control the foundation settlement. However, after the application of the long-long pile composite foundation technology in the collapsible loess area, not only the total settlement of the foundation is controlled, And it has also achieved good economic and social benefits. However, the previous research on its theory is not deep enough and perfect. Based on the high speed railway project under construction in collapsible loess area, this paper studies the settlement of long-long pile composite foundation systematically. The research contents of this paper are mainly reflected in the following aspects: First, after analyzing the working mechanism of long-long pile composite foundation under embankment load, the calculation formula of bearing capacity of long-long pile composite foundation is summarized. At the same time, several calculation methods of composite foundation settlement are summarized and analyzed. Secondly, two typical subgrade sections are selected and the additional stress of the foundation is calculated by the elastic earth embankment method Boussinesq triangle load method and Boussinesq combined load method. Then the settlement value of long-long pile composite foundation is calculated by the composite modulus method and the string modulus method, and compared with the measured settlement value, the settlement calculation method suitable for the long-long pile composite foundation in collapsible loess area is obtained. Thirdly, the numerical simulation of long-long pile composite foundation is carried out by using FLAC3D software. The Mohr-Coulomb model is used in the soil between piles. In the process of numerical calculation, the optimum depth is 3.5b, and the optimum width is 4.5b. With the increase of cushion modulus, the settlement of foundation increases and decreases respectively, and with the increase of the length of long pile and the modulus of soil above the end of short pile, the settlement of foundation decreases significantly. With the increase of the modulus of long pile and the modulus of length of short pile, the settlement of foundation is not obvious. Fourthly, according to the observation data of subgrade settlement in two test sections, the hyperbolic parabola method and BP neural network are used to predict the settlement. The model of BP neural network is constructed, the training and prediction of the samples are completed by MATLAB software. The fitting index R2 and relative error of the three prediction methods are calculated and compared. It is found that BP neural network is the most suitable for predicting the settlement of long-long pile composite foundation in collapsible loess area, and its fitting accuracy and prediction accuracy are very high.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU470

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