Fig. 7

An example of a time series for axial strain data is a causality test with different statistical tools such as (a) granger test, (b) granger test with increases lags more data points below or lies at significant levels (p-value less than 0.05), (c) ADF test for stationarily or non-stationary, and (d) WCP respectively at confining pressure condition of 5 MPa.