3D Roughness Measurement of Failure Surface in CFA Pile Samples Using Three-Dimensional Laser Scanning

Hyungjoon Seo

doi:10.3390/app11062713

Abstract

The bearing capacity of CFA (Continuous Flight Auger) pile is not able to reach the design capacity if proper construction is not performed due to the soil collapse at the bottom of the pile. In this paper, three pile samples were prepared to simulate the bottom of the CFA pile: grouting sample; mixture of grouting and gravel; mixture of grouting and sand. The failure surfaces of each sample obtained by a uniaxial compression tests were represented as a three-dimensional point cloud by three-dimensional laser scanning. Therefore, high resolution of point clouds can be obtained to simulate the failure surfaces of three samples. The three-dimensional point cloud of each failure surface was analyzed by a plane to points histogram (P2PH) method and a roughness detection method by kernel proposed in this paper. These methods can analyze the global roughness as well as the local roughness of the three pile samples in three dimensions. The roughness features of the grouting sample, the mixed sample of grouting and sand, and the mixed sample of grouting and gravel can be distinguished by the sections where points of each sample are predominantly distributed in the histogram of the proposed method.

Highlights

The CFA (Continuous Flight Auger) pile has been widely used in recent years on ground where soil collapse can occur in the borehole due to the groundwater flow
The sharp curves of the failure surface caused by the protrusion of the gravel and the area from which the gravel is separated from the failure surface are expressed as a distribution of points
The calculated five histograms were averaged in each sample

Summary

Introduction

The CFA (Continuous Flight Auger) pile has been widely used in recent years on ground where soil collapse can occur in the borehole due to the groundwater flow. Since the CFA pile is mainly constructed on weak ground conditions, studies have been conducted to estimate the bearing capacity and the behavior of CFA piles in various grounds (Farrell and Lawler, 2008, Gavin et al, 2009, Battista et al, 2016, Loveridge and Cecinato, 2016 [1,2,3,4,5,6,7,8,9,10]). This paper determined the behavior of the bottom of the pile affected by the soil collapse in the borehole along with the extension of this study. The roughness of the failure surface was evaluated with pile samples that simulate mixtures of grouting and soils at the bottom of the CFA pile

Methods

Results

Conclusion