本文選題：樁基礎(chǔ)　切入點(diǎn)：應(yīng)變楔形體模型　出處：《大連理工大學(xué)》2013年博士論文

【摘要】：樁基礎(chǔ)在當(dāng)前日益發(fā)展的土木工程基礎(chǔ)設(shè)施建設(shè)中得到了廣泛的應(yīng)用,而樁基礎(chǔ)不僅僅承擔(dān)著豎向荷載,同時(shí)也會(huì)承擔(dān)水平向荷載,特別在地震過(guò)程中,樁頭所支撐的上部結(jié)構(gòu)會(huì)產(chǎn)生很大的慣性力,使得鋼筋混凝土樁很容易進(jìn)入非線性狀態(tài),從而產(chǎn)生破壞,因此,如何合理地建立水平加載條件下考慮鋼筋混凝土樁的材料非線性的靜力分析方法是樁基礎(chǔ)抗震設(shè)計(jì)中重要的研究課題,對(duì)于軟土地區(qū)的水平加載樁,樁與其后側(cè)粘土的分離對(duì)樁基礎(chǔ)的水平承載性能有很大影響,如何在計(jì)算中考慮這一影響尚待研究,同時(shí),對(duì)于軟土地區(qū)的樁基礎(chǔ)會(huì)涉及到地基改良問(wèn)題,如何確定經(jīng)濟(jì)有效的改良深度也是個(gè)研究課題,另外,目前對(duì)于群樁基礎(chǔ)的水平承載力設(shè)計(jì)方法還不夠完善,需要做進(jìn)一步研究,同時(shí),在地震過(guò)程中,飽和砂土場(chǎng)地會(huì)產(chǎn)生砂土液化現(xiàn)象,而目前對(duì)于液化場(chǎng)地上群樁基礎(chǔ)抗液化性能的研究甚少,也是需要進(jìn)一步開(kāi)展的工作。本文圍繞著樁基礎(chǔ)做了以下研究工作： (1)針對(duì)現(xiàn)有的應(yīng)變楔形體模型存在的缺點(diǎn),如楔形體前破壞面不連續(xù)、應(yīng)力應(yīng)變路徑的公式比較復(fù)雜且參數(shù)不易選取、不適用于超固結(jié)粘土的計(jì)算等,本文提出了修正的應(yīng)變楔形體模型以用于樁基礎(chǔ)的水平響應(yīng)的計(jì)算,編制了SWPILE有限元程序,并通過(guò)已有文獻(xiàn)中大量的砂土、粘土以及層狀土中水平加載樁試驗(yàn),驗(yàn)證了該修正模型的可行性,并討論了應(yīng)變楔形體模型中的收斂問(wèn)題、楔形體中應(yīng)變和楔形體高度變化規(guī)律以及參數(shù)的敏感性等,最后,利用該修正的應(yīng)變楔形體模型研究了p-y曲線的影響因素； (2)基于修正的應(yīng)變楔形體模型,研究了雙層地基(密砂土和軟粘土)中樁基的水平響應(yīng),并研究了土的成層效應(yīng)對(duì)樁基水平響應(yīng)的影響規(guī)律,包括密砂土中的軟粘土夾層和軟粘土中密砂土夾層,在此基礎(chǔ)上,分析了密砂土場(chǎng)地和軟粘土場(chǎng)地中地表土層最大影響深度及其與計(jì)算出的楔形體高度的關(guān)系； (3)在修正的應(yīng)變楔形體模型中,采用纖維單元實(shí)現(xiàn)了水平加載條件下考慮鋼筋混凝土樁的材料非線性的計(jì)算,并根據(jù)已有文獻(xiàn)中的水平加載樁試驗(yàn)資料和計(jì)算結(jié)果,驗(yàn)證了該計(jì)算方法的可行性。利用該方法研究了鋼筋混凝土樁截面剛度在水平荷載作用下的變化規(guī)律以及樁的材料非線性對(duì)樁的撓度以及最大彎矩的影響；采用了單元應(yīng)力磨平的方法把纖維單元高斯點(diǎn)的應(yīng)力恢復(fù)到截面網(wǎng)格節(jié)點(diǎn)上,并繪制了截面的應(yīng)力云圖,從而了解了中性軸在不同荷載下的變化以及混凝土開(kāi)裂的發(fā)展情況； (4)在修正的應(yīng)變楔形體模型中引入了p-y乘子的概念來(lái)考慮群樁效應(yīng),并綜合了應(yīng)變楔形體模型和Mokwa等效單樁法的優(yōu)點(diǎn),提出了改進(jìn)的等效單樁法,通過(guò)已有文獻(xiàn)中的水平加載單樁與群樁實(shí)驗(yàn),驗(yàn)證了該方法的有效性,并基于該方法,研究了p-y乘子對(duì)不同位置(排)樁工況中計(jì)算出的p-y曲線的影響,并分析了不同深度處以及不同位置(排)樁工況中計(jì)算出的粘土和砂土的極限地基反力,還研究了水平荷載和場(chǎng)地深度對(duì)群樁效應(yīng)的影響以及不同樁頭條件對(duì)單樁和群樁基礎(chǔ)水平響應(yīng)的影響； (5)初步研究了液化場(chǎng)地樁基礎(chǔ)水平響應(yīng)計(jì)算方法�；谕暾恼鸷蠓课輷p壞調(diào)查資料,應(yīng)用完全耦合的動(dòng)力有限元方法再現(xiàn)了由砂土液化引起的房屋破壞情況,利用修正的Pastor-Zienkiewicz Mark-Ⅲ模型來(lái)模擬砂土在地震荷載作用下的液化特性,用三軸試驗(yàn)結(jié)果和標(biāo)準(zhǔn)貫入數(shù)據(jù)來(lái)確定該模型參數(shù),根據(jù)一組豎向分布的加速度傳感器記錄,采用SHAKE91程序確定了地震動(dòng)輸入,并把有限元計(jì)算出的地表水平位移與已有文獻(xiàn)中經(jīng)驗(yàn)公式計(jì)算出的結(jié)果以及震害調(diào)查的結(jié)果進(jìn)行了比較,從而驗(yàn)證了有限元計(jì)算結(jié)果的合理性,隨后,通過(guò)一系列的工況分析了邊坡對(duì)房屋震害的影響,并對(duì)比研究了群樁、水泥土、排水系統(tǒng)的抗液化性能,為液化場(chǎng)地上群樁基礎(chǔ)設(shè)計(jì)提供了計(jì)算方法和參考依據(jù)。
[Abstract]:Pile foundation has been widely used in the current development of the civil engineering infrastructure construction, and the pile foundation not only bear vertical load, but also bear the horizontal loads, especially during the earthquake, the upper structure supported by pile head will have a great inertia, the reinforced concrete pile easily into nonlinear the state, resulting in failure, therefore, how to establish the level of loading conditions considering material nonlinear static analysis method of reinforced concrete pile is an important research topic in the seismic design of pile foundation, the horizontal loaded pile in soft soil area, and the rear side of the clay pile separation level on pile foundation bearing performance greatly. How in the calculation of the influence is to be studied, at the same time, for the pile foundation in soft clay foundation improvement will involve the problem, how to determine the economic and effective reform Is a good research topic, also the depth, the horizontal bearing capacity of pile foundation design method is still not perfect, need to do further research, at the same time, during the earthquake, liquefaction of saturated sand ground will produce the phenomenon, but the research on liquefaction liquefaction resistance of pile foundation is very little, also need to be further the work carried out around the pile foundation. This paper does the following research work:
(1) according to the existing strain wedge model of the existing shortcomings, such as wedge before failure surface discontinuity, stress strain path formula is complicated and it is difficult to select parameters, not suitable for overconsolidated clay calculation, calculation is proposed in this paper. The strain wedge model modified for pile foundation level in response, the SWPILE finite element program, and through a large number of literatures in the sand, clay and horizontal layered soil loading pile test, verify the feasibility of the modified model, and discussed the convergence of strain wedge model, strain wedge and wedge height and the variation of parameter sensitivity finally, study the influence factors of p-y curve using the strain wedge model of the correction of the;
(2) the strain wedge model based on the study of double layered soil (dense sand and soft clay) in the lateral response of pile foundations, and studied the effects of pile horizontal layer effect response of the soil, including soft clay interlayer in dense sand and soft clay in dense sand interlayer, on the basis of analysis of dense sandy soil, ground and surface soil in soft clay and its maximum influence depth and calculate the wedge height relationship;
(3) in the modified strain wedge model, using the fiber element material nonlinear reinforced concrete pile considering the horizontal loading conditions, and according to the existing literature in the pile loading test data and calculation results, verify the feasibility of the method. The reinforced concrete pile section stiffness change the law under the action of horizontal load and deflection of pile pile material nonlinear and maximum bending moment effect by using this method; using unit stress to smooth fiber element Gauss points stress recovery section to nodes in the grid, and the section stress nephogram drawing, so as to understand the changes in the neutral axis under different loads, the crack of the concrete development;
(4) the strain wedge model modified in the concept of the p-y multiplier to consider the effect of pile group, and the comprehensive advantages of strain wedge model and Mokwa equivalent single pile method, improved equivalent single pile method, the horizontal loading in the literature of single pile and pile group experimental verification the effectiveness of the proposed method, and based on this method, the p-y multiplier in different position (row) p-y curve calculated in the condition of pile, and analyzes the different depth and different position (row) to calculate the pile condition in clay and sand limit subgrade reaction, are also studied influence of horizontal load and depth of field effect of pile group and different pile head conditions on single pile and pile group foundation level response;
(5) a preliminary study on the calculation method of pile foundation response level. After the complete housing damage based on investigation data, the dynamic finite element method fully coupled application reproduced by sand liquefaction caused by the destruction of houses, to simulate the characteristics of sand liquefaction under seismic loading using Pastor-Zienkiewicz Mark- III model, with the results three axis test and standard penetration test data to determine the model parameters according to the acceleration sensor records a group of vertical distribution, using SHAKE91 program to determine the seismic input, and compares the empirical formula of finite element to calculate the surface horizontal displacement and the calculated results and the results of earthquake damage investigation, rationality, and to verify the finite element calculation results subsequently, effect of slope on building damage are analyzed through a series of conditions, and compared the research group The anti liquefaction properties of pile, cement soil and drainage system provide the calculation method and reference for the design of pile group foundation on the liquefied site.

【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU473.1

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