Abstract
The influence of water on the mechanical properties of rock is vital for determining the rock stability when subjected to changes of water conditions. In this paper, a series of uniaxial compression tests were conducted to investigate effects of cyclic wetting and drying on the mechanical properties of sandstone and mudstone collected from Chongqing city, China. The results showed that both elastic modulus and uniaxial compressive strength of sandstone and mudstone were reduced by wetting and drying cycles, and that the degradation rate of the two mechanic parameters of mudstone was always larger than sandstone. The parameters, including water adsorption, degradation degree of elastic modulus, degradation degree of uniaxial compressive strength, increase with the increase of the wetting-drying cycles (N). The relationship between these three parameters and the value of N + 1 could be well fitted by logarithmic curves. The average degradation degree was also used to describe the degradation of per time wetting-drying cycles. It is found that the average degradation degree of elastic modulus and uniaxial compressive strength decrease with the increase of wetting-drying cycles. Moreover, the relationships between the mechanical properties and the porosity are presented, which can be fitted by linear curves. In the cyclic wetting-drying process, the elastic modulus and the uniaxial compressive strength decreased with the porosity increasing, and the degradation rates of sandstone mechanic parameters were higher than those of mudstone.
Highlights
Sandstone and mudstone are two common sedimentary rocks
In order to use the mixture of sandstone and mudstone particles reasonably in the civil engineering, the effect of cyclic wetting and drying on the mechanic properties of the parent rocks need to be studied first
The results indicated that the degradation with different degrees of the physical and mechanic properties of rock materials occurred after cyclic wetting and drying
Summary
Sandstone and mudstone are two common sedimentary rocks. It is well known that sandstone has been the most common construction material through human history all over the world due to its high strength, while mudstone is characterized by low permeability and high hydrophily, as well as easy softening and decay [1]. In Chongqing city of China, the strata composed of interbedded red sandstone and mudstone are widely distributed Because they are difficult to divide [2], the mixture of sandstone and mudstone particles is often used as a main fill material in many hydraulic and civil engineering works in Chongqing city [3]. While this material is filled in or along a large reservoir bank, it could be subjected to cyclic wetting and drying caused by cyclic lowering and rising of water level, which may affect the mechanical behavior of the mixture, and reduces stability of filled. In order to use the mixture of sandstone and mudstone particles reasonably in the civil engineering, the effect of cyclic wetting and drying on the mechanic properties of the parent rocks need to be studied first
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