基于离心模型试验的桩帽网结构路基桩端持力层效应研究

为了考察桩端持力层强度对桩帽网结构路基(地基)承载特性的影响,设计了4组不同桩端持力层状态的离心模型试验,测试了地基变形、加筋垫层拉力和路堤基底压力等数据。测试数据表明:①桩端持力层强度降低,地基由稳定向出现桩底明显刺入再到出现桩端持力层局部剪切破坏方面转化;②桩端持力层强度提高,地基变形减小,路基中心桩底刺入及地表沉降、坡脚地基水平变形均值与持力层承载力的关系曲线可用幂函数描述;③桩端持力层强度越高,桩体承载集中效应与桩间土承载减载效应越明显;④路基中心附近地表沉降与路基面覆盖范围筋带拉力均值间的关系曲线可用二次多项式描述,考虑了路堤横向滑移因素的筋带拉力计算值与实测较接近;⑤端承摩擦桩型的桩端持力层强度提高,筋带所受拉力减小;⑥布设袋装砂井,能加快地基的排水固结,提高桩端持力层承载力,增强地基稳定性。

Bearing stratum effect at pile end of pile-cap-net structure subgrade based on centrifugal model tests

To investigate the effect of the strength of bearing stratum at pile end on the bearing behavior of pile-cap-net structure subgrade (foundation), four groups of centrifuge model tests, separately with different bearing stratum situations at pile end, are designed. The deformation of foundation, tensile force in reinforced cushion, and vertical compression at the bottom of embankment are recorded. The test data show that: ①with the decrease of the strength of bearing stratum at pile end, the foundation turns from stability to the status with stab deformation of pile end and then to the status with local shear failure in bearing stratum at pile end; ②with the increase of the strength of bearing stratum at pile end, the deformation of the foundation reduces. The relationship between the stab deformation of pile end under subgrade center, foundation surface settlement, average value of horizontal foundation deformation under slope toe and the bearing capacity of bearing stratum at pile end can be described as the power function; ③with the increase of the strength of bearing stratum at pile end, the bearing concentration effect of piles and the bearing attenuation effect of soil between piles become obvious; ④the relationship between the foundation surface settlement under subgrade center and the average value of tensile force in reinforced belt under subgrade surface is described as the quadratic polynomial. The calculated values of reinforced belt force considering embankment lateral sliding are relatively close to the test data; ⑤with the increase of the strength of bearing stratum at end-support friction pile end, the force in the reinforced belt decreases; ⑥the layout of sand wick can accelerate the drainage consolidation of foundation and improve the bearing capacity of bearing stratum at pile end and enhance the stability of foundation.