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

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-bearing 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 belled 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 small 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 bearing 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.