【摘要】：黃土溝谷地區(qū)雨水和橋梁上部結(jié)構(gòu)排水長期沖刷作用下，橋梁樁周護(hù)坡產(chǎn)生不同程度的沖刷破壞，使單排雙柱式樁基產(chǎn)生承載能力不足、沉降與不均勻沉降等諸多問題。直接影響樁基結(jié)構(gòu)的正常使用和安全性，，對橋梁上部結(jié)構(gòu)的正常工作也產(chǎn)生極大隱患。 首先，在對樁基不同沖刷病害進(jìn)行識別的基礎(chǔ)上，結(jié)合對典型病害進(jìn)行的原因分析，建立了樁基水流沖刷破壞過程模型，并在此基礎(chǔ)上提出針對沖刷破壞的樁基混凝土結(jié)構(gòu)承載能力和耐久性評估方法。其次，在分析沖刷破壞對樁基豎向和橫向承載能力影響時，結(jié)合沖刷破壞后樁背側(cè)向土壓力對樁身的作用機理，通過建立在豎向力、橫向力和彎矩共同作用下的樁基復(fù)雜受力模型，得出了基于“m”法的樁身撓曲方程，分析了樁身水平位移、轉(zhuǎn)角、彎矩、剪力和樁側(cè)土抗力的變化規(guī)律，分析結(jié)果有助于對復(fù)雜受力狀態(tài)下的樁基承載能力及安全狀態(tài)作出評定。最后，在樁基加固方案初步設(shè)計的基礎(chǔ)上，通過有限差分軟件FLAC3D，使用NULL單元進(jìn)行沖刷過程模擬、ELASTIC、SHELL和CABLE單元進(jìn)行加固過程的模擬，建立了樁基典型沖刷病害全程數(shù)值模擬樁-土模型，分析了樁-土模型矢量變形、位移、樁身應(yīng)力、摩阻力、錨桿力在沖刷-加固全程中的變化，對結(jié)構(gòu)體系最大不平衡力和關(guān)鍵點進(jìn)行了全程跟蹤。通過數(shù)值計算結(jié)果可知，樁周土體沖刷破壞使樁身產(chǎn)生橫向撓曲、樁身出現(xiàn)拉應(yīng)力、產(chǎn)生反彎點、沉降值過大、承載能力不足等諸多問題，使樁基處于極不安全的狀態(tài)，通過樁底高壓噴射注漿形成固結(jié)體、土體中打入錨桿和混凝土護(hù)面，能夠有效改善樁基不利受力，使整個樁-土體系處于較為安全的狀態(tài)。 本文針對不同沖刷破壞程度提出的加固關(guān)鍵技術(shù)和坡面防護(hù)技術(shù)相結(jié)合的加固方案初步設(shè)計可操作性強、加固效果明顯，能夠有效的解決實際工程中的問題，為今后同類問題的解決有借鑒意義。
[Abstract]:Under the long-term scour action of Rain Water and superstructure drainage in loess gully area, the slope protection around the bridge pile produces different degree of scour damage, resulting in many problems such as insufficient bearing capacity of single row double-column pile foundation, settlement and uneven settlement and so on. It directly affects the normal use and safety of pile foundation structure, and also has great hidden danger to the normal work of bridge superstructure. Firstly, on the basis of identifying the different erosion diseases of pile foundation, combined with the analysis of the causes of the typical diseases, the model of pile foundation erosion failure process is established. On this basis, a method for evaluating the bearing capacity and durability of pile foundation concrete structures with scour failure is proposed. Secondly, when analyzing the influence of erosion failure on the vertical and lateral bearing capacity of pile foundation, combined with the action mechanism of lateral earth pressure on pile body after erosion failure, through the establishment of vertical force, The complex force model of pile foundation under the action of transverse force and bending moment is obtained. The deflection equation of pile body based on "m" method is obtained, and the variation law of horizontal displacement, rotation angle, bending moment, shear force and soil resistance of pile side is analyzed. The analysis results are helpful to evaluate the bearing capacity and safety state of pile foundation under complex loading condition. Finally, on the basis of the preliminary design of the reinforcement scheme of pile foundation, through the finite difference software FLAC3D, the NULL element is used to simulate the scouring process and the CABLE element is used to simulate the strengthening process. The pile-soil model for the whole process of typical erosion disease of pile foundation is established, and the variation of vector deformation, displacement, stress of pile body, friction resistance and anchor force in the whole course of scouring and strengthening are analyzed. The maximum unbalanced force and key points of the structure system are tracked in the whole process. The results of numerical calculation show that the soil scour failure around the pile causes the pile body to produce transverse deflection, the pile body appears tensile stress, produces the reverse bending point, the settlement value is too large, the bearing capacity is insufficient and so on, so the pile foundation is in an extremely unsafe state. The consolidation body is formed by high pressure jet grouting at the bottom of the pile, and the anchor rod and the concrete surface are pushed into the soil, which can effectively improve the unfavorable force of the pile foundation and make the whole pile-soil system in a relatively safe state. In this paper, according to different scour failure degree, the key technology of reinforcement and slope protection technology are put forward. The preliminary design of reinforcement scheme is feasible, and the effect of reinforcement is obvious, which can effectively solve the problems in practical engineering. It can be used for reference for solving similar problems in the future.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：U443.15;U445.72

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