Macro/Microtesting and Damage and Degradation of Sandstones under Dry-Wet Cycles

Xinrong Liu,Wen Yuan,Zijuan Wang,Luli Miao,Yan Fu

doi:10.1155/2016/7013032

Xinrong Liu, Wen Yuan + Show 3 more

Open Access

https://doi.org/10.1155/2016/7013032

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Abstract

In terms of the degradation of mechanical parameters of rock mass in the hydrofluctuation belt of a reservoir bank slope arising from rainfall and the reservoir level fluctuation, the moderately weathered sandstone in a side slope of the Three Gorges Reservoir Region is selected as a research object to carry out “drying-saturation-drying” tests for disks with two thicknesses (h=25 mm,h=50 mm) in different cycles; a spiral CT machine, an ultrasonic velocity meter, and a light Schmidt hammer are utilzed to conduct nondestructive testing on dry-wet cycles; through the Brazilian splitting test, the uniaxial tensile strength of “dry” and “saturated” sandstones under different dry-wet cycles is obtained. The research shows that, with the increase of the dry-wet circles (n), the longitudinal wave velocity and the rebound strength of sandstones are linearly decreased withn; the uniaxial tensile strength of sandstones and the mean CT number of cross sections are logarithmically decreased withn; the fitting equation of macro/micromechanical parameters and dry-wet cycles (n) of sandstones is raised, which is provided as a reference basis for the weathering process of sandstones under dry-wet cycles.

Highlights

The softening of sandstones by water absorption is a strength and stiffness reduction phenomenon caused by physical action [1,2,3]
Affected by rainfall or reservoir water circulation, it will be in a “water absorption-air drying” state
For the hydrofluctuation belt of the Three Gorges Reservoir Region, the water level difference is up to 30 m, which has a huge impact on the stability of the reservoir slope [7,8,9,10,11,12,13]

Summary

Introduction

The softening of sandstones by water absorption is a strength and stiffness reduction phenomenon caused by physical action [1,2,3]. Jeng et al [18, 19], Hale and Shakoor [20], and Reviron et al [21] carried out discussions on the mechanical property of sandstones under dry-wet cycles, but different test results were obtained, and the degradation mechanism of sandstones caused by dry-wet cycles remained unclear In recent years, such methods as CT scanning, ultrasonic velocity testing, and rebound method have gradually emerged to test the damage degree of sandstones. Through the approximate simulation of drywet cycles in the “drying-saturation-drying” process in a laboratory, as well as the “ultrasonic-CT-rebound” integrated testing method and Brazilian splitting test, the change rule of sandstone strength and deformation caused by dry-wet cycles is researched, the test results are analyzed and concluded, and the change rule and damage evolution characteristics of macro/micromechanical parameters of sandstones under dry-wet cycles are obtained and provided as a reference for relevant engineering designs

Experimental

Results and Discussion

1-1-25 AB-25 Vertical-25

Research on the Change Rule of Rebound

Conclusion