Slope stability calculation method for highwall mining with open-cut mines

Area of Science:

• Geotechnical Engineering
• Mining Engineering

Background:

• Slope stability is a critical challenge for highwall mining, particularly in residual coal extraction under steep conditions.
• Overlying strata can weaken the basal coal seam, potentially altering slope failure mechanisms from circular to sliding along weak layers.

Purpose of the Study:

• To develop a concept of target time pillar strength for assessing coal pillar service life.
• To establish a quantitative method for evaluating slope stability influenced by highwall mining operations.

Main Methods:

• Creep tests were conducted to determine time-varying coal shear strength parameters under various loads.
• Regression analysis was used to establish a time-varying function for shear strength.
• Numerical modeling assessed the impact of bearing stress and target time strength on yielding zone development.
• Rigid body-limit equilibrium theory was applied to develop a slope stability calculation method.

Main Results:

• A time-varying function for coal shear strength parameters was established.
• Highwall mining length was categorized into goaf, yielding, and elastic zones based on structural plane theory.
• Temporal and spatial evolution patterns of weak layer shear strength parameters were identified.
• The influence of bearing stress and target time strength on yielding zone evolution was quantified.

Conclusions:

• The proposed target time pillar strength concept and the new slope stability calculation method effectively quantify mining impacts.
• These methods are significant for advancing the application and promotion of highwall mining technology, especially in challenging geological settings.