框架码头大直径钢护筒嵌岩桩基工作性状研究

发布时间：2018-04-15 06:21

本文选题：大直径钢护筒嵌岩桩 + 试验研究　；参考：《重庆交通大学》2015年博士论文

【摘要】：本文结合国家科技支撑计划《三峡水库常年回水区航运工程建设关键技术研究(2011BAB09B01)第4专题“深水码头嵌岩桩基础承载性状及设计技术研究”,依托重庆港果园作业区二期扩建工程,通过室内单桩物理模型对比试验、码头钢护筒嵌岩桩基的系列数值模拟分析并借助相应的物模试验成果验证,对内河框架码头钢护筒嵌岩桩基在竖向和水平力作用下的受力性状、钢护筒与混凝土界面特性分别进行了研究,获得的主要研究成果如下:(1)根据大小比尺单桩对比试验结果,在竖向荷载作用下,钢护筒嵌岩桩工作性状与一般嵌岩桩大致相同;在水平荷载作用下,钢护筒嵌岩桩与普通嵌岩桩失效模式不同,普通嵌岩桩破坏面倾斜且在地基表面附近,钢护筒嵌岩桩破坏面水平,且横穿钢管底部。(2)在水平荷载作用下,受压侧钢护筒-混凝土界面粘结较好,受拉侧界面发生滑移;拉应力显著大于压应力,结构受力状态较差。(3)大直径钢护筒嵌岩单桩由于侧阻力增加,垂直承载能力提高,桩嵌岩深度增加,但承载能力增加不大,护筒嵌岩深度的经济合理嵌深大约为(1~2)D(D为桩径);钢护筒能增加水平承载力,减少位移,可减小桩身拉应力及缩小拉应力区域,钢护筒段抗弯能力显著增加,但在护筒底端有突变。(4)框架码头排架中各钢护筒嵌岩桩均呈现桩顶位移最大、岩面处接近零,各桩位移基本相同且明显小于无钢护筒情况;最大负弯矩在桩顶、最大正弯矩在岩面处,岩面以上段明显大于无钢护筒情况,嵌岩段变化不大,最大弯矩出现在后列桩;剪力在横撑处有突变、嵌岩段反向,最大剪力也出现在后列桩;嵌岩段轴力上下两端小、中间大,最大轴力出现在前列桩。(5)岩体弹性模量大,钢护筒嵌岩桩位移小;粘聚力和内摩擦角变化,对嵌岩桩桩身位移和弯矩影响不大。(6)框架码头排架中桩基与岸坡的施工顺序和岸坡填筑方式对钢护筒嵌岩桩的工作性状有明显影响,先填筑岸坡(岸坡稳定)后施工桩基可大大减少桩基位移和内力,分层填筑好于一次填筑,高岸坡、陡岸坡更应先填筑后成桩。(7)码头水位增高,排架中各钢护筒嵌岩桩的位移、弯矩、剪力均增加;水位降幅和降速变化,对后两列桩的位移和轴力、对前列桩的横向力影响较大。(8)依据前述试验和数值分析,综合考虑了嵌固深度、岩体模量、桩径、水平荷载作用点位置、岩体性质和结构重要性等多方面因素影响,提出了大直径钢护筒嵌岩桩嵌固深度简化计算公式,经与实际工程对比,吻合较好,可供软质岩中大直径钢护筒嵌岩桩基水平承载力的设计计算时参考。
[Abstract]:Combined with the National Science and Technology support Plan < Research on key Technologies in the Construction of Shipping Engineering in the perennial backwater area of the three Gorges Reservoir (2011BAB09B01), the fourth special topic, "Research on bearing behavior and Design Technology of Rock-socketed pile Foundation in Deep Water Wharf", is presented in this paper.Based on the second phase expansion project of Chongqing Port Orchard Operation area, the series of numerical simulation analysis of the rock-socketed pile foundation of the steel retaining tube of the wharf and the verification of the corresponding physical model test results are carried out through the comparative test of the physical model of the single pile in the laboratory.In this paper, the mechanical behavior of the rock-socketed pile foundation of the inland river frame wharf under the action of vertical and horizontal forces and the characteristics of the interface between the steel guard and the concrete are studied separately. The main research results obtained are as follows: 1) according to the results of comparison test of single pile with size scale,Under vertical load, the working behavior of steel retaining tube rock-socketed pile is approximately the same as that of general rock-socketed pile, and under horizontal load, the failure mode of steel-protected barrel rock-socketed pile is different from that of ordinary rock-socketed pile, and the failure surface of common rock-socketed pile is inclined and near the ground surface.Under the action of horizontal load, the interface between steel retaining tube and concrete in compression side is bonded well, slip occurs in the interface of tension side, and the tensile stress is significantly larger than the compressive stress.The stress state of the structure is poor. (3) because of the increase of lateral resistance, the vertical bearing capacity and the depth of rock socketed pile are increased, but the bearing capacity is not increased.The economical and reasonable depth of the rock-socketed depth of the retaining tube is about 1 / 2 / D as the diameter of the pile, and the steel tube can increase the horizontal bearing capacity, reduce the displacement, reduce the tensile stress of the pile and reduce the area of the tensile stress, and the bending resistance of the steel pipe can be increased significantly.However, there is a sudden change at the bottom of the retaining tube. 4) in the bent frame of the frame wharf, the pile top displacement is the largest, the rock face is near zero, the displacement of each pile is basically the same and obviously smaller than that of the steel retaining tube, and the maximum negative bending moment is on the pile top.The maximum positive bending moment is at the rock face, the above section is obviously larger than the case of no steel retaining tube, the rock socketed section has little change, the maximum bending moment appears in the back row pile, the shear force is abrupt at the horizontal brace, the rock socketed section is reverse, the maximum shear force also appears in the back row pile.The axial force of rock socketed segment is small in both ends and middle, and the maximum axial force appears in the front row pile. 5) the elastic modulus of rock mass is large, the displacement of rock-socketed pile in steel retaining tube is small, the cohesive force and the angle of internal friction change,The construction sequence of pile foundation and bank slope in the frame wharf and the filling mode of bank slope have obvious influence on the working behavior of the rock-socketed pile with steel retaining tube. The influence of the displacement and bending moment of the rock-socketed pile body is not significant on the construction sequence of the pile foundation and the bank slope in the frame wharf.The displacement and internal force of pile foundation can be greatly reduced by first filling bank slope (bank slope stabilization) and then construction pile foundation. The layered filling is better than the first filling, and the high bank slope and steep bank slope should be filled first and then become pile. 7) the water level of the wharf is increased, and the displacement of the rock-socketed piles of each steel retaining tube in the row frame is increased.Bending moment and shear force increase, water level decrease and velocity drop change, the displacement and axial force of the latter two piles and the transverse force of the front row pile are greatly affected.) according to the above test and numerical analysis, the embedded depth, the modulus of rock mass and the diameter of pile are considered synthetically.Based on the influence of many factors, such as the position of the action point of horizontal load, the nature of rock mass and the importance of structure, a simplified formula for calculating the embedded depth of large diameter steel retaining tube socketed pile is put forward, which is in good agreement with the actual engineering.It can be used as a reference for the design and calculation of horizontal bearing capacity of large diameter steel pipe socketed pile foundation in soft rock.
【学位授予单位】：重庆交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U656.1

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