Characteristics of Gravelly Granite Residual Soil in Bored Pile Design: An In Situ Test in Shenzhen

Shuai Luan,Fenglai Wang,Tiehong Wang,Weihou Shui,Zhao Lu

doi:10.1155/2018/7598154

Abstract

Granite residual soil is widely distributed in south China and is treated as a special soil. Its design parameters in rotary drilling bored piles are a matter of debate due to lack of in-situ pile load tests. Back-analysis of test piles is a reliable means of studying the geotechnical capacity of granite residual soil for pile design. In this study, a series of in situ tests was conducted comprising six full-scale instrumented test piles in gravelly granite residual soil in Shenzhen to consider the effects of different construction methods. The six piles were constructed with three different rotary drilling methods. Two commonly used design methods were investigated in the back-analysis: the SPT and effective stress methods. The results of the loading tests and strain gauges were used to obtain the back-analyzed parameters of the ultimate shaft resistance and ultimate base resistance for gravelly granite residual soil with these two design methods.

Highlights

Granite residual soil is a soil-like decomposed granite with weathering grades of VI, V, and IV
Granite residual soil is generally classified as silty sand or sandy silt depending on the particle size distribution and according to the American Society for Testing and Materials (ASTM) and British Standards Institution (BSI) [7]
A series of experiments was conducted to study the pile shaft resistance and pile base resistance of rotary drilling bored piles in gravelly granite residual soil, including six surveyed boreholes with standard penetration test (SPT) and borehole samples

Summary

Introduction

Granite residual soil is a soil-like decomposed granite with weathering grades of VI, V, and IV. Erefore, Chinese engineering practicing needs effective stress and SPT methods such as alternative design methods and supplements to IL method in bored pile design in granite residual soil area. A series of experiments was conducted to study the pile shaft resistance and pile base resistance of rotary drilling bored piles in gravelly granite residual soil (which can be classified as silty sand according to ASTM D2487 [27]), including six surveyed boreholes with SPT and borehole samples. E results were used to back-analyze the ultimate shaft and base resistances of these piles, and the parameters of granite residual soil with the SPT and effective stress methods were examined. En, the influence of the construction method on the vertical bearing capacity of bored piles in granite residual soil was considered Six test piles were subjected to the static loaded test. e results were used to back-analyze the ultimate shaft and base resistances of these piles, and the parameters of granite residual soil with the SPT and effective stress methods were examined. en, the influence of the construction method on the vertical bearing capacity of bored piles in granite residual soil was considered

Materials and Methods

Materials

Experimental Setup

Results and Discussion

200% design working load

Conclusion