持力层对大直径扩底灌注桩竖向承载性状的影响

Influences of bearing stratum on vertical bearing behaviors of large diameter cast-in-place belled piles

大直径扩底灌注桩的沉降以桩端土层的竖向压缩变形为主,因此端承土层特性对大直径扩底桩的竖向承载性状有较大影响。利用有限差分程序建立三维非线性有限差分数值模型,研究了持力层性质对大直径扩底桩竖向承载性状的影响。结果表明,大直径扩底桩承载力随持力层厚度的增加而增大,且在持力层厚度较小时持力层厚度的变化对承载力和桩端阻力影响显著。桩侧土层模量与持力层模量比为0.2时,桩端入持力层深度的变化在持力层厚度较小时对大直径扩底桩的极限承载力影响较大。相同持力层厚度下,桩侧土层模量的变化对大直径扩底桩承载力的影响较大,模量越大承载力越高;下卧层模量的变化对大直径扩底桩承载力的影响较大。

The main vertical deformation of large diameter cast-in-place belled piles is the compressive one of end-bearing stratum. So the properties of the end-beating stratum have a great effect on the vertical bearing behavior of the large diameter belled piles. In order to analyze the effectiveness of the bearing stratum on the vertical bearing behavior of a belied pile, three-dimensional non-linear finite-difference numerical models are established by means of the finite-difference program. It is found that the vertical bearing capacity of a large diameter belled pile increases with the increment of the thickness of the bearing stratum. Both the bearing capacity and the tip resistance are notably affected when the thickness variation of the bearing stratum is on the stnall side. When the ratio of the modulus between the shaft stratum and the bearing stratum is 0.2, the ultimate bearing capacity of the large diameter belled pile is greatly affected as the variation of the tip embedded depth of the pile when the thickness of the bearing stratum is on the small side. With the same thickness of the beating stratum, the bearing capacity of the large diameter belled pile is greatly affected as the variation of the modulus of the shaft stratum. The greater the modulus of the bearing stratum is, the greater the bearing capacity is. The bearing capacity of the large diameter belled pile is greatly affected with the variation of the modulus of the bearing substratum.