摘要
交通量的迅速增长使越来越多早期建成的高速公路需要拓宽改建,而软基路段新老路基变形协调控制是主要技术难题之一。以沪宁高速公路镇江段扩建工程中采用粉喷桩处理的典型软基路段为背景,考虑老路基先期固结,采用FLAC3D程序分析桩长、桩距、桩侧摩阻力、铺设土工格栅与否及填土速率等对新老路基变形协调的影响。其过程为先分析桩长与桩距的影响,然后在此基础上分析其他因素的影响。研究结果表明:桩长和桩距对拓宽路基的影响最为显著,桩长过大对减小沉降无太大意义,桩距过大则不能满足沉降控制要求,计算断面合理的桩长为进入持力层2.5 m左右,且合理桩距为1.1m。实际桩侧摩阻力相对设计值降低量不超过50%时,其对路基沉降的影响较小;有桩和桩帽时在路基底铺设土工格栅对减小路基沉降和不均匀沉降的作用很小。路堤填土速率较大时对沉降速率有一定影响,但对累计沉降基本无影响,小于10kPa/d的加载速率是可行的。基于以上结果,确定优化的路基处治方案,通过沉降监测证明计算结果与实测结果基本相符,拓宽路基沉降满足设计要求。
Due to the rapid increase of traffics,more and more early-built expressways will be reconstructed;and the control of differential settlements between old and new roadbeds on soft foundation is one of the key technical issues.Focusing on a typical soft foundation segment treated with dry jet mixing（DJM） piles in the Shanghai— Nanjing expressway widening project,the influences of pile length,pile distance,pile lateral friction force,geogrid and construction rate to the coordinated deformation between old and new roadbeds are analyzed with FLAC^3D programme.The procedure is firstly analyzed for the influence of different pile lengths and distances on the deformations of soft foundation.Then,based on the proposed pile length and distance,the influences of pile lateral friction force with/without laying geogrid and construction rate are considered.The results indicate that pile length and distance are the most significant influential factors while the others are relatively minor ones.It is also shown that the excess pile length has little effect on settlement reduction;and excess pile distance can not meet the settlement control standard.It is suggested that the rational pile length is to ensure piles embedded in supporting soil layer about 2.5 m,and the rational pile distance is about 1.1 m.If actual pile lateral friction force is not 50% lower than the designed value,the influence is comparatively small on post-construction and differential settlements.Considering laying geogrid over the soft foundation treated with piles and pile caps has not distinct improvement on differential settlements;and the construction rate has potential influence on settlement rate but little influence on accumulated settlements with a loading rate of 10 kPa/d.According to the above results,an optimized treatment scheme for widening soft foundation is advanced and adopted.The settlement monitoring results show that the numerical calculation results agree well with the actual settlements;and the settlements indexes can meet the reque
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2008年第2期309-315,共7页
Chinese Journal of Rock Mechanics and Engineering
关键词
公路工程
路基拓宽
软基
变形
沉降计算
highway engineering
subgrade widening
soft foundation
deformation
settlement calculation
