基于振动台试验对不同桩体加固液化土变形特性的研究

发布时间：2018-04-09 09:55

  本文选题：砂土液化　切入点：振动台试验　出处：《太原理工大学》2017年硕士论文

【摘要】：液化土加固问题一直是岩土工程重点关注及研究的课题。碎石桩和水泥土桩被广泛应用于液化土地基处理。碎石桩的排水、挤密效果以及水泥土桩对地基竖向承载力的提高效果均在实际工程中得到了普遍的认可。但其对液化土加固的机理研究仍有不足,需要进一步深入研究及科学试验的认证。本文依托国家自然基金“桩体加固液化砂土作用机理的试验研究”(项目号50578104)、山西省交通厅科技项目“黄土地区桩体加固砂土抗液化机理的研究”(合同编号10-1-06)以及山西省交科院黄土实验室开放基金项目“液化土层桩基础承载性状的试验研究”(KLTLR-Y13-3),展开以液化土地基加固机理为背景、以1:18的相似几何比模拟地表以下8.64m范围内的砂土液化土层震害情况的研究,通过三组液化模型即碎石桩加固液化土模型、水泥土桩加固液化土模型以及碎石桩与水泥土桩复合加固液化土模型分别进行振动台试验,记录不同加固模型不同埋深、不同水平位置处的孔隙水压力、土压力及位移时程曲线并进行整理分析得出如下结论:宏观现象反映:不论哪种加固模型,在循环荷载振动作用下,桩顶均出现排水,且随着碎石桩根数的增加,排水量逐渐增多,振动结束后,整体表面呈凹状并向振动方向倾斜,且局部出现沙丘,碎石桩加固模型下部土体密实,水泥土桩加固模型土体上部密实,碎石桩和水泥土桩复合加固模型土整体呈现较密实。由孔隙水压力分析得出:(1)不论哪种加固模型,孔隙水压力时程曲线均随振动荷载施加孔隙水压力值增大,达到峰值保持几秒后,随振动开始缓慢下降,直到试验结束。(2)同一种加固模型,孔隙水压力均随埋深的加深不断增大;(3)同一位置处,水泥土桩加固模型的孔隙水压力最大,复合桩加固模型次之,碎石桩加固模型最小,说明碎石桩提供了良好的排水通道,有助于孔隙水压力的消散。由土压力分析得出:(1)不论哪种加固模型,土压力时程曲线均随振动荷载施加土压力在静压力附近上下波动几秒后,土压力迅速下降到最小值,随后以此定值波动直到试验结束;同一水平面上,0cm处的土压力减小量最小,-14cm处次之,14cm处最大。(2)同一加固模型土压力均随着埋深的加深不断增大;(3)相同位置处,碎石桩加固模型的土压力最大,水泥土桩加固模型次之,复合桩加固模型最小,比较相同条件下,复合桩加固模型中桩体分担的土压力最大。(4)土压力与埋深、水平位置三者关系满足p=z_0+ax+by+cx~2+dy~2+fxy(y—埋深/cm;x—水平位置/cm;p—土压力/kpa;z0,a,b,c,d,f—与加固模型有关的系数)关系式,由此可推算出三种加固模型不同位置的土压力。由沉降量分析得出:(1)不论哪种加固模型,振动开始几秒沉降量均不变,随振动继续,沉降量迅速到最大,之后以此值保持到试验结束;同一埋深平面沉降呈凹型并倾斜,且随着埋深的加深,凹沉的曲率减小;(2)相同水平位置处,随着埋深的增加,沉降量在不断的减小,且随着碎石桩根数的增加,沉降量逐渐减小;(3)沉降量与埋深和水平位置的关系为:s=z_0+ax+by+cx~2+dy~2+fxy(y—埋深,单位cm;x—水平位置,单位cm;S—沉降量,单位mm;Z_0,a,b,c,d,f—与加固模型有关的系数)关系式。可以用此式推算出三种加固模型任一位置的沉降量。总之,无论哪种桩体加固模型,桩体中部容易发生膨胀和断裂;且相同条件下,复合桩加固模型中桩体分担的土压力最大;水泥土桩加固的沉降量大于复合桩加固,碎石桩加固的最小,说明碎石桩加固有利于抑制土体沉降。因此,从综合因素考虑,建议实际工程尽量考虑采用碎石桩与水泥土桩复合加固形式加固液化土。
[Abstract]:The problem of soil liquefaction reinforcement has been the focus of attention and research of geotechnical engineering subject. Gravel pile and cement soil pile is widely used in the treatment of liquefied soil foundation. The drainage gravel pile, and the compaction effect of soil cement pile foundation vertical bearing capacity and improve the effect in practical engineering has been widely accepted. But the study on the mechanism of liquefaction of soil reinforcement is still inadequate, need further research and scientific test certification. Experimental study of the National Natural Science Foundation "pile reinforcement mechanism of sand soil liquefaction based on" (Project No. 50578104), on the loess area of pile reinforcement sand soil anti liquefaction mechanism of Shanxi provincial Department of Communications Science and technology project "(" the contract number 10-1-06) experimental study on bearing behavior of pile foundation and soil liquefaction in Shanxi province Jiaoke hospital laboratory loess open fund project "(KLTLR-Y13-3), launched in the liquefied soil foundation reinforcement The mechanism for the background, in a similar study than in the sand soil liquefaction damage simulation of 8.64m under the surface within the scope of the geometry of the 1:18, through three sets of liquefied model gravel pile liquefied soil model, the soil cement pile reinforcement and soil liquefaction model of gravel pile and cement soil pile composite reinforcement soil liquefaction model are respectively used in shaking table test, record different reinforcement model of different depth, pore water pressure in different horizontal positions, soil pressure and displacement curve and analysis draws the following conclusion: macroscopic phenomena reflect: no matter what kind of reinforcement model, cyclic loading in vibration under the pile top are drainage, and with the increase of gravel pile root number, drainage the amount gradually increased, after the vibration, the whole surface is concave and is inclined to the direction of vibration, and the emergence of local sand dunes, the gravel pile model of lower soil compaction, soil cement pile and soil on the solid model Department of dense, gravel pile and cement soil pile composite reinforcement model of soil showed relatively compact. The pore water pressure is obtained by analysis: (1) no matter what kind of reinforcement model, pore water pressure curve with the vibration load imposed by the pore water pressure increases and the peak hold after a few seconds, with vibration began to decrease slowly. Until the end of the experiment. (2) with a reinforcement model, pore water pressure increases with the depth of further increasing; (3) at the same position, the pore water pressure of soil cement pile reinforcement model, composite pile reinforcement model of gravel pile reinforcement model that provides the minimum drainage gravel pile a good channel, contribute to the dissipation of pore water pressure. The earth pressure obtained by analysis: (1) no matter what kind of reinforcement model, soil pressure curve with the vibration load of earth pressure in the static pressure near the fluctuation after a few seconds, the earth pressure decreases to the minimum value, with the 鍚庝互姝ゅ畾鍊兼尝鍔ㄧ洿鍒拌瘯楠岀粨鏉，

本文编号：1725919