A direct shear apparatus for intact rock under dynamic moisture content

Area of Science:

• Geotechnical Engineering
• Rock Mechanics
• Material Science

Background:

• Rock moisture content fluctuates with environmental conditions, affecting mechanical properties during prolonged creep.
• Understanding these changes is vital for assessing the stability of rock masses in engineering applications.

Purpose of the Study:

• To investigate the influence of moisture content variations on the long-term shear strength and deformation of intact rock.
• To develop and validate a specialized shear apparatus capable of simulating dynamic moisture changes.

Main Methods:

• A novel shear apparatus was designed with fluid injection ports allowing alternate water and gas injection to control rock moisture content.
• The apparatus utilizes silicone gaskets and seals to maintain high fluid pressures (5 MPa) without leakage during testing.
• Shear creep tests were performed on argillaceous shale under constant and dynamic moisture conditions, with results modeled using the Nishihara model.

Main Results:

• Significant differences in long-term shear strength and deformation behavior were observed in argillaceous shale subjected to varying moisture content.
• The developed apparatus successfully controlled and monitored moisture content changes under sustained loading conditions.

Conclusions:

• The study demonstrates that moisture content is a critical factor influencing the shear creep properties of rocks.
• The novel rock shear apparatus facilitates quantitative analysis of rock behavior under changing moisture, offering practical value for predicting engineering rock mass stability, especially during rainfall events.