Calculation Approach for Lateral Bearing Capacity of Single Precast Concrete Piles with Improved Soil Surrounds

Guangyin Du,Liye Li,Anhui Wang,Dingwen Zhang

doi:10.1155/2018/5127927

Abstract

Precast concrete (PC) piles with cement-improved soil surrounds have been widely used for soft ground improvement. However, very few calculation approaches have been proposed to predict the lateral bearing capacity. This study aims at investigating the lateral capacity of a single PC pile reinforced with cement-improved soil through a series of 3D finite element analyses and theoretical studies. It is revealed that application of cement-improved soil around the PC pile can obviously reduce the induced lateral deflections and bending moments in the pile and can significantly increase its capacity to resist lateral loading. To account for the reinforcement effect of cement-treated soil, a modified m approach is proposed by introducing a modified coefficient to enable the predictions of the lateral bearing capacity for such reinforced PC piles. It is revealed that the modified coefficient is approximately linearly related to the compressive bearing capacity of improved soil surrounds.

Highlights

Deep cement-mixing (DCM) column has many advantages, such as a large volume, limited environmental disturbance, rapid construction, and low cost, so it is extensively used in soft ground improvement
The DCM column strength is significantly affected by soil conditions, which results in a low column uniformity and poor reinforcement effect [1]
In order to evaluate the e ect of cement-improved soil surrounds on the lateral bearing performance of a precast concrete (PC) pile, the Midas/GTS software was used to establish threedimensional models of PC piles with and without improved soil surrounds under lateral loading, according to the full-scale pile load tests. e test project was performed in Nantong, which is located along the southeast coast of China

Summary

Introduction

Deep cement-mixing (DCM) column has many advantages, such as a large volume, limited environmental disturbance, rapid construction, and low cost, so it is extensively used in soft ground improvement. To solve the abovementioned problems, the PC pile with improved soil surrounds, produced by inserting a PC pile into a DCM column before the initial setting of cement-improved soil (Figure 1), has recently been proposed [1, 2] In this way, the high-strength PC pile is designed to bear a load, and the improved soil surrounds act to transfer axial force into the surrounding soils by skin frictions [2]. Wang et al [13] and He et al [14] carried out monotonic and cyclic lateral loading tests to investigate the contributions of the jet-grouting column reinforcement to improve the lateral performance of the single cast-in-place pile. Eld observations and numerical modeling of laterally loaded piles with jet-grouting or cement-mixing column reinforcement have been reported, systematic studies pertaining to the contributions of cement-treated soil surrounds to the lateral capacity of PC piles are still somewhat lacking. A modi ed m approach accounting for the cement-improved soil reinforcement was proposed for the reinforced piles within the cohesive soil, and the suitability of the proposed m approach for predicting the lateral bearing capacity of such reinforced piles was assessed

Numerical Simulations

16 Silty sand

Modified m Approach for PC Piles with Improved Soil Surrounds

Conclusions