【摘要】：樁基礎(chǔ)的承載能力主要取決于樁周土的極限承載能力,土的強(qiáng)度主要體現(xiàn)在抗剪強(qiáng)度上。因此,土的抗剪強(qiáng)度指標(biāo)是決定樁基礎(chǔ)承載力的主要因素。土的強(qiáng)度參數(shù)包括黏聚力c和內(nèi)摩擦角φ,目前,這兩個(gè)參數(shù)的取得通常是通過土工試驗(yàn)完成,包括直接剪切試驗(yàn)、三軸壓縮試驗(yàn)等。但由于土工試驗(yàn)需要將試樣脫離其工作環(huán)境,而且無法精確地模擬真實(shí)工作條件下土的破裂面,因此土工試驗(yàn)得到的強(qiáng)度參數(shù)存在較大誤差。國(guó)內(nèi)外專家通過一系列改進(jìn)的試驗(yàn)來模擬土的真實(shí)工作狀態(tài),但仍未能完全達(dá)到預(yù)期目標(biāo)。本文根據(jù)樁周土材料受力特性與三軸壓縮試驗(yàn)中土樣的力學(xué)特性的關(guān)聯(lián)性分析,分別研究了樁側(cè)土和樁端土的應(yīng)力狀態(tài)；應(yīng)用彈性力學(xué)理論,推導(dǎo)了1/4無限平面彈性體在一側(cè)受到均布正應(yīng)力和均布切應(yīng)力的條件下的應(yīng)力解,使用明德林解求解樁端地基單元的應(yīng)力,進(jìn)而確定土單元破裂面,求解其第一主應(yīng)力和第三主應(yīng)力；結(jié)合巖土材料離散的特性,提出了樁側(cè)土的應(yīng)力衰減系數(shù),進(jìn)而應(yīng)用莫爾-庫(kù)倫準(zhǔn)則和應(yīng)力路徑理論提出反分析方法—莫爾應(yīng)力圓圖解法,求解土的強(qiáng)度參數(shù)。對(duì)于樁側(cè)土,采用本文推導(dǎo)的樁側(cè)土單元應(yīng)力解,求解樁側(cè)土單元應(yīng)力并應(yīng)用衰減系數(shù)公式進(jìn)行修正,通過應(yīng)力路徑理論,確定樁側(cè)土極限平衡狀態(tài)所在位置。對(duì)于樁端土,采用集中力作用于地基內(nèi)部條件下的明德林解計(jì)算樁端土有效壓縮層厚度范圍內(nèi)的土單元應(yīng)力,通過應(yīng)力路徑理論,確定樁端土極限平衡狀態(tài)所在位置。然后,分別對(duì)黏性土材料和無黏性土材料應(yīng)用對(duì)應(yīng)的莫爾應(yīng)力圓圖解法,確定樁周土的黏聚力和內(nèi)摩擦角。在建立強(qiáng)度參數(shù)反分析方法后,應(yīng)用混凝土灌注樁靜載荷試驗(yàn)的荷載和位移數(shù)據(jù),對(duì)混凝土灌注樁樁周土材料強(qiáng)度參數(shù)反分析求解,將反分析得到的強(qiáng)度參數(shù)分別應(yīng)用于有限元強(qiáng)度折減法、荷載增量法的極限荷載分析,荷載增量法計(jì)算的P-s曲線較好的擬合了靜荷載試驗(yàn)P-s曲線；使用有限元強(qiáng)度折減法研究了樁基礎(chǔ)的極限荷載問題,進(jìn)一步證明本文提出的莫爾應(yīng)力圓圖解法可以求解滿足工程設(shè)計(jì)要求的強(qiáng)度參數(shù)。
[Abstract]:The bearing capacity of pile foundation mainly depends on the ultimate bearing capacity of soil around pile, and the strength of soil is mainly reflected in shear strength. Therefore, the shear strength index of soil is the main factor to determine the bearing capacity of pile foundation. The strength parameters of soil include cohesion force c and internal friction angle 蠁. At present, these two parameters are usually obtained by geotechnical tests, including direct shear test, triaxial compression test and so on. However, because the geotechnical test needs to separate the specimen from its working environment, and can not accurately simulate the fracture surface of the soil under the real working conditions, there is a big error in the strength parameters obtained from the geotechnical test. Experts at home and abroad simulate the real working state of soil through a series of improved experiments, but they still fail to achieve the expected goal. According to the correlation analysis between the stress characteristics of soil around pile and the mechanical properties of soil samples in triaxial compression test, the stress states of soil on pile side and soil at pile end are studied in this paper. Based on the theory of elasticity, the stress solution of 1 鈮，

本文編號(hào)：2505810