论文部分内容阅读
高速铁路对路基变形要求严格,长短桩加固黄土地基在消除浅层黄土湿陷性、提高地基承载力、控制路基整体沉降和不均匀沉降方面有优势。本文结合室内模型试验,研究不同桩长比η(η=短桩桩长/长桩桩长)、不同短桩间距对长短桩复合地基沉降及长桩承载特性的影响。试验表明:桩长比、桩间距对沉降的影响均较大,桩长比越大、桩间距越小,复合地基沉降越小,其对黄土地基的加固效果越明显;随着桩长比增大、桩间距减小,长桩桩身应力、桩土应力比和荷载分担比均减小;当荷载为120kPa时,η=0.5、0.75、1的复合地基沉降较天然地基分别减少54.4%、73.0%、83.1%;η=0.5,桩间距为3.5 D、3 D、2.5 D时复合地基沉降较天然地基分别减少45.3%、60.56%、76.6%;不同桩长比、不同桩间距的桩土应力比随荷载增加先增大后减小。以上分析表明,在实际工程中宜综合分析地质条件、荷载水平、施工难度和工程成本,合理选用短桩长度和桩间距。
High-speed railway has strict requirements on subgrade deformation. Long-short pile reinforcement of loess foundation has advantages in eliminating collapsibility of shallow loess, improving foundation bearing capacity, controlling subgrade settlement and uneven settlement. In this paper, the effect of different pile length ratio η (η = short pile length / long pile length) and different short pile spacing on the settlement of long and short pile composite foundation and the bearing characteristics of long piles are studied in this paper. The results show that the influence of pile-length ratio and pile-spacing on settlement is larger, the pile-length ratio is larger, the distance between piles is smaller and the settlement of composite foundation is smaller, and the reinforcement effect on loess foundation is more obvious. When the load is 120kPa, the settlement of composite foundation with η = 0.5,0.75,1 decreases by 54.4% compared with that of natural foundation, and the settlement of pile foundation decreases with the increase of pile spacing, 73.0% and 83.1%, respectively. When η = 0.5 and the pile spacing is 3.5 D, the settlement of composite foundation is reduced by 45.3%, 60.56% and 76.6% respectively compared with natural foundation. The stress ratio first increases and then decreases with the increase of load. The above analysis shows that in the actual project should be a comprehensive analysis of geological conditions, load levels, construction and engineering costs, the rational use of short piles and piles.