河北沿海高速公路软土地基变形规律及沉降预测研究

发布时间：2018-04-15 07:36

本文选题：软土地基 + 复合地基　；参考：《长安大学》2015年博士论文

【摘要】：本文依托河北沿海高速公路实际工程,对水泥搅拌桩复合地基和塑料排水板竖向排水体地基设计了软土地基变形试验观测方案,采用测斜导管、沉降板、孔隙水压力计和土压力计等测试方法,对软土地基填筑期、预压期和卸荷再加载三个阶段进行了长达2年多的全过程监测,通过现场试验和理论分析,取得了以下主要研究成果:1.分析研究了两种不同地基处理方式下软土地基沉降、水平位移及孔隙水压力变化规律。填筑期水泥搅拌桩复合地基沉降仅为塑料排水板地基的7.64%~25.70%,最终沉降预测值仅为塑料排水板地基的8.76%~28.9%,不设预压期的水泥搅拌桩工后沉降预测值为不设预压期塑料排水板地基的6.78%~25.01%,为设2个月预压期塑料排水板地基的8.51%~36.46%。填筑期水泥搅拌桩复合地基最大沉降为最大水平位移的3.7~4.1倍,而塑料排水板地基最大沉降为最大水平位移的8.6~15.3倍。由以上分析可见,水泥搅拌桩复合地基可显著减小软基工后沉降和填筑期水平位移,更适合工后沉降要求较高的桥头路段和快速填筑路段。2.水泥搅拌桩复合地基填筑期沉降、最终沉降预测值和工后沉降预测值均随桩间距的增大而明显增加,填筑期末桩间距为1.4m的地基沉降分别为桩间距1.2m和1.0m地基沉降的1.79倍和2.91倍,最终沉降预测值分别为1.2m和1.0m最终沉降预测值的1.67倍和2.79倍,工后沉降预测值分别为1.2m和1.0m工后沉降预测值的1.58倍和2.63倍。因此通过对桥台后一定长度范围内水泥搅拌桩桩间距的调整形成沉降过渡段,从而有效地减少“桥台跳车”病害。3.水泥搅拌桩复合地基桩顶、桩间土压力和桩土应力比均随所加荷载的增加而逐渐增加,基本为线性关系,但桩顶压力的增幅为桩间土压力增幅的8.65~12.3倍,桩间距为1.4m的桩土应力比分别为桩间距1.2m和1.0m桩土应力比的1.39倍和2.57倍;建议在桩间距为1.0m~1.4m时该地区桩土应力比为2~6。4.补充了沉降系数综合计算公式中地基处理类型修正值,经分析计算建议水泥搅拌桩复合地基修正值为0.85~0.95;沉降系数综合计算公式计算的沉降系数与反算系数非常接近且公式计算值略大,并建议该地区沉降系数为1.05~1.15。5.通过对费尔哈斯曲线模型的时间因子进行指数修正,提出了指数型费尔哈斯曲线模型,改进后的模型沉降预测值与实测值保持较高的相关性,并能得到较满意的最终沉降预测结果。通过对分析计算,推荐该地区修正指数为1.5。6.基于MATLAB建立了水泥搅拌桩复合地基和塑料排水板地基的BP神经网络预测模型,该模型仿真预测结果与指数型费尔哈斯模型预测结果非常接近,但较双曲线法和新野法预测值增加6.4%~42.87%。因此,BP神经网络预测模型和指数型费尔哈斯曲线模型较好地解决了其它沉降曲线模型最终沉降量预测偏小的问题。7.对工后沉降研究表明,塑料排水板地基一般路段可不设预压期,但在等载甚至超载条件下,塑料排水板法用于涵洞或箱形通道时均应设置不小于2个月的预压期。这一结果表明该地区预压期可小于现行《公路路基设计规范》中关于竖向排水体处治法预压期不宜小于6个月的规定。
[Abstract]:This paper relies on the Hebei coastal highway engineering, the composite foundation of cement mixing pile and plastic drainage plate vertical drains design of soft soil foundation deformation observation scheme, using inclinometer tubes, settlement plate, pore water pressure and soil pressure meter test method for filling soft soil foundation period, the period of preloading and unloading bearing loading in three stages for more than 2 years of monitoring, through field test and theoretical analysis, the main results are as follows: 1. analysis of the two different methods of foundation treatment under the soft soil foundation settlement, lateral displacement and pore water pressure. The composite pile foundation settlement is only plastic drainage the 7.64%~25.70% foundation board of filling cement mixing, the prediction of final settlement value is only the plastic drainage plate foundation 8.76%~28.9%, a cement mixing pile under pre settlement prediction value for the precompression term Plastic drainage plate foundation 6.78%~25.01%, 3.7~4.1 times for a 2 month period of preloading with plastic drainage plate foundation 8.51%~36.46%. filling cement mixing pile composite foundation for the maximum settlement of the maximum horizontal displacement, and the plastic drainage plate foundation maximum settlement is the maximum horizontal displacement 8.6~15.3 times. By the above analysis shows that, can obviously reduce the soft foundation after filling the settlement and horizontal displacement of cement mixing pile composite foundation, the bridge sections requiring high and fast filling sections of.2. cement filling pile composite foundation settlement is more suitable for the industry, the prediction of final settlement value increased significantly with the increase of pile spacing and settlement prediction and after filling the final pile spacing of 1.4m the settlement of the foundation settlement of pile spacing were 1.2m and 1.0m foundation 1.79 times and 2.91 times, the prediction of final settlement value were 1.2m and 1.0m in the prediction of final settlement value of 1.67 times and 2.79 times. Settlement prediction values were 1.2m and 1.0m post construction settlement prediction value of 1.58 times and 2.63 times. So the settlement of transitional section formed by the abutment after a certain length of cement mixing pile spacing adjustment, so as to effectively reduce the pile composite foundation top disease.3. cement abutment jump, pile soil pressure and the pile-soil stress ratio increases with the increasing load and gradually increased linearly, but the pressure on the top of the pile in soil between piles pressure increase 8.65~12.3 times, pile spacing of pile soil stress ratio of 1.4m pile spacing 1.2m and 1.0m pile soil stress ratio of 1.39 times and 2.57 times respectively; in pile spacing of 1.0m~1.4m pile and soil stress ratio in the region added type correction value calculation formula in the treatment of foundation coefficient of settlement for the 2~6.4., the calculated correction value for 0.85~0.95 pile composite foundation of cement mixing coefficient of the comprehensive settlement proposal; The settlement coefficient calculation formula and inverse coefficient is very close to the calculated value and the formula is slightly larger, and suggested that the area sedimentation coefficient of 1.05~1.15.5. by the time factor on Verhulst curve model of exponent, presents exponential Verhulst curve model, the improved model of settlement prediction value to maintain a high correlation with the measured. And can get a satisfactory prediction of final settlement results. Through the analysis, the recommendation of the area correction index for 1.5.6. based on MATLAB BP neural network prediction model is established the composite foundation of cement mixing pile and plastic drainage plate foundation, the model simulation results and forecast index prediction results Verhulst model closely, but compared with the hyperbolic method and Xinye prediction value increased 6.4%~42.87%. therefore, prediction model and exponential Phil Haas curve model can solve the BP neural network The settlement curve of final settlement prediction model of small.7. of settlement after construction of plastic drainage plate foundation general sections not to set the pre pressing period, but in the other load even under overload conditions, plastic drainage method for culvert box or channel shall be not less than 2 months of pre compression period. This result indicates that the area of preloading period can be less than the current "specifications for design of highway subgrades > on vertical drainage body treatment preloading period of not less than 6 months.

【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U416.1

【参考文献】