Numerical investigation of soil plugging effect inside sleeve of cast-in-place piles driven by vibratory hammers in clays.

Yong Jie Xiao,Yi Zhi Dong,Fu Quan Chen

doi:10.1186/s40064-016-2423-y

Abstract

During driving sleeve of cast-in-place piles by vibratory hammers, soils were squeezed into sleeve and then soil plugging was formed. The physic-mechanical properties of the soil plug have direct influence on the load transmission between the sleeve wall and soil plug. Nevertheless, the researches on this issue are insufficient. In this study, finite element and infinite element coupling model was introduced, through the commercial code ABAQUS, to simulate the full penetration process of the sleeve driven from the ground surface to the desired depth by applying vibratory hammers. The research results indicated that the cyclic shearing action decreases both in soil shear strength and in granular cementation force when the sleeve is driven by vibratory hammers, which leads to a partially plugged mode of the soil plug inside the sleeve. Accordingly, the penetration resistance of sleeve driven by vibratory hammers is the smallest compared to those by other installation methods. When driving the sleeve, the annular soil arches forming in the soil plug at sleeve end induce a significant rise in the internal shaft resistance. Moreover, the influence of vibration frequencies, sleeve diameters, and soil layer properties on the soil plug was investigated in detail, and at the same time improved formulas were brought forward to describe the soil plug resistance inside vibratory driven sleeve.

Highlights

It is well-known that the installation of pipe piles may lead to soil plugging
The main conclusions were as followings: (1) During vibratory sleeve driving, the soil strength and cohesion decrease, which is induced by cyclic shearing action
Soil plug is partially-plugged, and the penetration resistance is less than those by other installation methods; (2) In the vibratory penetration process, annular soil arches form inside the soil plug, which induces an obvious increase in internal shaft resistance

Summary

Introduction

It is well-known that the installation of pipe piles may lead to soil plugging. the existence of the soil plug leads to an increase in vertical bearing capacity and the penetration resistance as well (Gavin and Lehane 2003).The phenomenon is well-known, but little is known about the mechanism of soil plug formation inside pipe piles, especially for the sleeve driven by vibratory hammers. It is well-known that the installation of pipe piles may lead to soil plugging. The existence of the soil plug leads to an increase in vertical bearing capacity and the penetration resistance as well (Gavin and Lehane 2003). The phenomenon is well-known, but little is known about the mechanism of soil plug formation inside pipe piles, especially for the sleeve driven by vibratory hammers. The formation of a soil plug depends upon a number of factors, e.g. installation method, pile diameter, penetration depth, soil density, whereas the investigation on the influencing factors are still not complete. A lot of researches were conducted to evaluate the soil plugging effect during pipe pile driving. Based on the principle of static equilibrium, Randolph et al (1991) developed the concept of active height of soil plug and established

Methods

Results

Conclusion