Abstract
To identify mechanism of sand particle size effect on the mechanical properties of gypsum cement, 11 grades of sand particles with a size of 0.1–3 mm were used to produce 99 specimens for uniaxial compression and permeability coefficient testing. Based on this, the distribution characteristics of internal stress and horizontal displacement are discussed using the numerical analysis. The results obtained show that the sand particle size effect on the uniaxial compressive strength of similar materials is negatively correlated within the range from −16.51% to 49.79%. SEM observations imply that, in the case of small particle sizes, gypsum crystals develop into denser needle-like structures, while for larger particle sizes, they are mostly loose lamellar structures. Permeability tests indicated that the larger the sand particle size, the greater the permeability, indicating that the internal pore connectivity is better, and the crevices are easier to penetrate when the specimen is compressed. Numerical simulations indicated that the larger the particle size, the larger the extreme deformation value of the specimen in the horizontal direction, and the more uneven the deformation distribution. In addition, specimens with larger particle sizes had a larger total area, where the tensile stress exceeded the ultimate tensile strength, and were more prone to tensile failure.
Highlights
Similar simulation experiments are important research method commonly used in geotechnical engineering, in particular, in coal mining
In order to ensure that the sand particle size of similar simulation materials is similar to the internal structure size of the rock, excessively large sand particles were excluded from the simulation test
The following conclusions were drawn: 1. The particle size of sand in gypsum cement has a strong effect on the compressive strength of the material
Summary
Similar simulation experiments are important research method commonly used in geotechnical engineering, in particular, in coal mining. In the experiments in Urumqi, the main critical layer was not broken These differences can be attributed to several influencing factors, including sand particle. Related studies have found that the particle size of sand has a great effect on the strength of cemented similar materials [18,19]. This paper studies the variation of axial compressive strength of gypsum-cemented similar materials under 11 different particle size conditions. The main contributions of the study are as follows: Firstly, the effect of particle size on mechanical properties of gypsum-cemented similar materials was obtained, which provided basic support for improving the experimental accuracy of similar simulation of rock-soil. The internal deformation characteristic and stress distribution of the specimen were explained, which clarified the changing characteristics of the internal mechanical environment of the cemented material under pressure
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