堆载降水预压强夯联合法加固汕头软土路基试验研究

发布时间：2018-11-20 06:30

【摘要】：以汕头沿海经济带的大范围吹填场地的高等级公路地基处理工程为依托，通过现场试验研究典型路段采用堆载降水预压强夯联合法加固软土地基的加固机理，分析地基变形、孔隙水压力随时间的变化规律、强夯的动力特性、强夯在软土地基固结中的作用、处理后软土路基的加固效果,此基础上对试验路段建立软土固结有限元数值分析模型，将计算结果与现场监测数据作对比，得到如下结论：（1）现场采用二级堆载填土加降水及两次强夯加固软土地基。加固后②1层淤泥的粘聚力值由8.7kPa提高到18.6kPa，④1层淤泥质土的粘聚力值由17.2kPa提高到29.85kPa；地基承载力特征值大于120kPa。（2）现场试验历时210d，固结总沉降527mm，其中第一级堆载填土1.3m，历时95d，固结沉降279mm，，强夯结束后，固结沉降428mm；第二级堆载填土2m，历时110d，固结沉降62mm，强夯结束后，固结沉降99mm；第一次强夯结束后沉降最大值为149mm，占总沉降量的28%。第二次强夯结束后引起的沉降最大值为82mm，占总沉降量的15.7%，强夯加固作用效果明显。（3）超孔隙水压力在软基处理过程中，变化最大值都是位于强夯期间，增高最大值达到10kPa左右，经过2d后恢复到强夯前超孔隙水压值，强夯施工的两遍点夯最佳间隔时间大于2d。（4）强夯作用下测点的加速度峰值随着测点与夯点距离的增加而不断衰减，同一测点竖直方向加速度值最大是水平方向的2.4倍,强夯的水平影响范围在15~20m左右；从对同一夯点的多遍夯击来看，第三遍夯击测得的加速度值最大，前两遍夯击能大部分消耗在对表层土的压密过程中。（5）数值模拟结果表明，在填土阶段数值模拟结果与现场实测监测的沉降曲线比较一致。在两次堆载过程中，第一级填土数值模拟的沉降值与现场监测数据相比大2.8%；但第二级填土数值模拟的沉降值比现场监测数据小13%。
[Abstract]:Based on the foundation treatment project of high grade highway in Shantou coastal economic belt, the consolidation mechanism of soft soil foundation strengthened by heaped precipitation preloading and dynamic compaction method is studied by field test, and the deformation of foundation is analyzed. The variation law of pore water pressure with time, the dynamic characteristics of dynamic compaction, the effect of dynamic compaction in consolidation of soft soil foundation, the reinforcement effect of soft soil subgrade after treatment, and the finite element numerical analysis model of consolidation of soft soil in test section are established. By comparing the calculation results with the field monitoring data, the following conclusions are obtained: (1) the second stage heaped fill and precipitation and twice dynamic compaction are used to reinforce the soft soil foundation in the field. The cohesion of 21 layers of silt is increased from 8.7kPa to 18.6 KPA and the cohesion of 41 layers of silt is increased from 17.2kPa to 29.85 KPA, and the characteristic value of foundation bearing capacity is more than 120 KPA. (2) the site test lasted 210 days, and the total consolidation settlement was 527mm, among which 1.3m, 95 days, 279mm, 428mm after dynamic compaction; The second stage of loading fill is 2 m, lasting 110 days, the consolidation settlement is 62 mm, the consolidation settlement is 99 mm after the completion of the dynamic compaction, and the maximum settlement is 149 mm after the first dynamic compaction, accounting for 28% of the total settlement. The maximum settlement caused by the second dynamic compaction is 82 mm, accounting for 15. 7 mm of the total settlement, and the effect of dynamic compaction is obvious. (3) during the treatment of soft foundation, the maximum change of excess pore water pressure is in the period of dynamic compaction, the maximum value of the increase reaches about 10kPa, and after 2 days, it recovers to the value of excess pore water pressure before dynamic compaction. The optimum interval time of double point ramming is more than 2 days. (4) the acceleration peak of the measured point decreases continuously with the increase of the distance between the measuring point and the tamping point. The maximum vertical acceleration of the same measuring point is 2.4 times that of the horizontal direction, and the horizontal influence range of the dynamic compaction is about 15 ~ 20m; According to the multiple tamping at the same tamping point, the acceleration measured by the third tamping is the largest, and most of the first two tamping energies are consumed in the compaction process of the surface soil. (5) the numerical simulation results show that the numerical simulation results are in good agreement with the measured settlement curves in the filling stage. In the course of two heaps, the settlement value of the first stage filling numerical simulation is 2.8 larger than that of the field monitoring data, but the settlement value of the second stage filling numerical simulation is 13% smaller than that of the field monitoring data.
【学位授予单位】：河北大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U416.1

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