An approach on modelling of in-situ deformations for unstable coal mine slopes

Twelve unstable slopes have been observed in four different coal mines of the General Directorate of Turkey Coal Enterprises (TKİ) for the last 12 years. A total of 131 theodolite, inclinometer and extensometer stations have been established for monitoring unstable slopes. According to the measurement results, the magnitude of the deformation values in all of the stations ranges from 0 to 10,978 mm. The database shows that time dependent deformation is formed in three consecutive stages. The form of the first stage is logarithmic, the second stage is linear and the third stage is exponential. To ensure control of the unstable slope, precautions must be taken during the second stage, or the beginning of the third stage at the latest according to observations, measurements and previous experience. To express time dependent deformation behaviour for unstable slopes, a graphical presentation of the mathematical model was developed. By means of statistical analysis of the database, a mathematical model was prepared. The model is characterized by three stages of deformation behaviour. In addition, the model can be presented in sub-deformation curves for each stage. The sum of the sub-deformation curves are equal to the predicted deformation curve. However, in this study, it is named as the predicted total deformation. Velocity and acceleration behaviours were determined by taking first and second derivatives of the time dependent predicted total deformation curve. Therefore, all stages of the deformation can be determined. In addition, a classification based on deformation behaviour for unstable slopes was suggested.