Method of estimating the effective zone induced by rapid impact compaction

Shih-Hao Cheng,Louis Ge,Shi-Shuenn Chen

doi:10.1038/s41598-021-97912-1

Abstract

This paper proposes a method for estimating the effective zone, including effective depth and effective range of compaction degree, from rapid impact compaction (RIC) on sand layer whose fines content is less than 10%. The proposed method utilizes a string of microelectromechanical system accelerometers to monitor the acceleration at various depths and propagation distances during compaction. To interpret and extract useful information from monitored data, peak-over-threshold (POT) processing and normal distribution function were used to analyze the recorded acceleration. The mean and standard deviation of the threshold peak acceleration were used to evaluate the effective depth and the effective range of compaction degree during RIC compaction. Moreover, spatial contours were used to determine the correlation of the threshold peak acceleration against depth and propagation distance from the RIC impact point. These contours help indicating the distribution of the effect zone after compaction. Lastly, a proposed method is suggested for frequent use in trial tests to quickly determine RIC’s required depth and impact spacing.

Highlights

The RIC method involves using a hydraulic hammer installed on a compactor with a fall height of 1.2–1.5 m and frequency of 30–60 blows/min to impact cohesiveless soils, such as sand, silty sand and gravel
When the site investigation indicates that the trial compaction cannot achieve the required depth or compaction degree, the impact energy, including the foot weight, fall height and blow count must be adjusted until the design requirements are met before a formal construction can be launched
The proposed method can be performed at any impact point in the test area using a string of microelectromechanical system (MEMS) accelerometers to simultaneously record the soil particle acceleration induced by impact energy at various depths and various propagation distances under field conditions

Summary

Introduction

The RIC method involves using a hydraulic hammer installed on a compactor with a fall height of 1.2–1.5 m and frequency of 30–60 blows/min to impact cohesiveless soils, such as sand, silty sand and gravel. This study evaluates the effective zone that used SAA string to monitor the particle acceleration induced by the soil shear distortion at various depths and propagation distances during the RIC. When the RIC foot impact ground, it is necessary to synchronize the SAA string to monitor the soil particle accelerations at any impact point selected from the trial test area.

Results

Conclusion