Influence of fines on the compression behaviour of decomposed volcanic rocks

Ismail Adeniyi Okewale

doi:10.1186/s40703-019-0101-y

Abstract

The compression behaviour of mixtures of sand with fines derived from decomposed volcanic rocks has been investigated in details. Oedometer tests were carried out on the samples of different degrees of weathering. The data show that no unique normal compression lines can be identified. The soils have medium degree of convergence and the degree of convergence is reducing with increasing fines. An attempt was made to investigate the particle breakage to further highlight the compression behaviour in a quantitative way. Soils with similar initial gradings have different particle breakage as a result of different degrees of weathering and the breakage can be linked to the quantity of larger particles. The particle breakage reduces as the amount of fines increases for the soils and when analysed the particle breakage further, it was observed that the more weathered volcanic samples have weaker particles.

Highlights

Numerous studies have been carried out on the influence of fines, mineralogy and particle breakage on the mixtures of soils consisting of different grain size and types (e.g. [18, 22, 26, 28])
Despite the fact that several works have been carried out on the mechanics of behaviour of adding fines to sand, there are still some disagreements on the behaviour of binary mixtures of sand. While it is less clear what the values of transitional fines should be for different soils and how the nature of the fines influences the mechanics of compression behaviour of soils studied by Zuo and Baudet [28], Lade and Yamamuro [11] and Carrera et al [2] found that as the fines increase, the minimum value of compressibility and the lowest location of normal compression line in the v: lnp’ plane being a transitional mixture
At the highest stress reached in the tests, it is not possible to identify a unique one-dimensional normal compression lines (NCL) for the different mixtures, indicating that the compression paths do not converge to a unique NCL

Summary

Introduction

Numerous studies have been carried out on the influence of fines, mineralogy and particle breakage on the mixtures of soils consisting of different grain size and types (e.g. [18, 22, 26, 28]). This work is different from the study of Xiao et al [24] which investigated transitional behaviour in a well graded coarse granular soil with very small fines content (about 1.8%) and large amount of large size particles (93% > 2.36 mm) in shearing. They studied the critical state behaviour of coarse granular soil. Particle breakage is investigated to shed more light on the compression behaviour of volcanic soils of different weathering degrees This was achieved by carrying out oedometer tests on different mixtures of samples of two degrees of weathering from different depths and locations of Hong Kong Island. The original samples are well-graded but due to heterogeneous nature of weathering processes and different

60 ArƟficial grading curves of different mixtures of CDV and HDV are the same

Results and discussions

Conclusions