组合桩地基抗液化特性研究

发布时间：2018-08-14 09:10

【摘要】：组合桩作为一种较新的桩基形式结合了水泥土和钢筋混凝土两种材料的优势,利用钢筋混凝土内芯来承担主要的上部荷载,借助外侧水泥土搅拌桩与土体大的接触面提供较高的侧摩阻力,具有施工方便、承载力高的优点,因而在黄泛区可广泛应用。虽然部分学者进行了黄泛区饱和粉土地震液化特性试验研究,但针对该地区如何提高地基的抗液化能力,尤其是减轻液化影响桩基的措施,并未进行深入探讨。传统改善地基液化条件处理的措施,仍有各自的局限性。组合桩充分利用水泥土和钢筋混凝土两种材料的的优点,技术优势明显。但是强震作用下组合桩抗液化性能的研究并未看到相关研究文献,可见理论研究落后于工程实际应用。本文通过借助有限差分分析软件Flac3d分析了地震作用下组合桩的抗液化性能。文章分别讨论了组合桩单桩和组合桩群桩在不同条件下的抗液化性能,总结其影响地基土孔隙水压力和超孔压比时程变化的一般规律,并初步探讨了组合桩地基孔隙水压力的解析算法,得出如下结论。1.组合桩改变了地震作用下地基土的孔隙水压力分布,孔隙水压力在桩端附近出现集聚区域。2.在水平方向随着距桩芯距离的增大,孔隙水压力的振动变化不明显,距离桩芯位置最远的监测点,地震作用下迅速达到峰值并保持相对稳定且从超孔压比判断局部时刻出现液化状态。3.水泥土范围的改变影响孔隙水压力集聚区域的位置,使其向远离桩芯的方向偏移,在桩周附近,孔隙水压力及超孔压比的时程变化明显即孔隙水压力的消散效果较好4.水位线的改变,影响孔隙水压力的分布,增长了孔隙水压力的消散路径,但影响效果有限。5.组合桩群桩的抗液化效果更加明显,桩间距的增加孔隙水压力集聚区域向边界偏移,且该区域孔隙水压力最大值降低,单桩间距的增加加大了群桩的抗液化影响范围。6.对组合桩地基孔隙水压力解析解算法的边界及定解条件进行了初步探讨,一维情况下孔隙水压力分布的计算结果与模拟情况在趋势上较为吻合。
[Abstract]:As a new type of pile foundation, the composite pile combines the advantages of cement-soil and reinforced concrete. The inner core of reinforced concrete is used to bear the main upper load, and the large contact surface between cement-soil mixing pile and soil provides high lateral friction. It is convenient to construct and has high bearing capacity, so it is in the Yellow River flooding area. Although some scholars have carried out the experimental study on the seismic liquefaction characteristics of saturated silt in the Yellow River flooding area, how to improve the anti-liquefaction capacity of the foundation, especially the measures to reduce the impact of liquefaction on the pile foundation, has not been discussed in depth. However, the research on the liquefaction resistance of composite piles under strong earthquakes has not seen the relevant literature, which shows that the theoretical research lags behind the practical application of engineering. The paper discusses the anti-liquefaction performance of single pile and composite pile groups under different conditions, summarizes the general rules of the influence of the anti-liquefaction performance of single pile and composite pile groups on the variation of pore water pressure and pore pressure ratio of foundation soil, and preliminarily discusses the analytical algorithm of pore water pressure of composite pile foundation, and draws the following conclusions. 1. The distribution of pore water pressure and the accumulation area of pore water pressure appear near the pile tip. 2. With the increase of the distance from the pile core in the horizontal direction, the variation of pore water pressure is not obvious, and the monitoring point farthest away from the pile core can reach the peak value quickly and keep relative stability under earthquake action. Liquefaction occurs at all times. 3. The change of cement-soil range affects the location of pore water pressure accumulation area and makes it shift away from the pile core. In the vicinity of the pile, pore water pressure and excess pore pressure ratio have obvious time-history changes, i.e. the dissipation effect of pore water pressure is better. 4. The change of water level affects the distribution of pore water pressure and the growth of pore water pressure. The dissipation path of pore water pressure is found, but the effect is limited. 5. The anti-liquefaction effect of composite pile group is more obvious. The pore water pressure accumulation area shifts to the boundary with the increase of pile spacing, and the maximum pore water pressure decreases in this area. The increase of single pile spacing enlarges the anti-liquefaction influence range of composite pile group. 6. The boundary conditions and definite solution conditions of analytical pressure solution algorithm are preliminarily discussed. The results of pore water pressure distribution in one-dimensional case are in good agreement with the simulation results.
【学位授予单位】：河南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU473.1;TU435

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