Reasonable depth of the borehole for in-situ stress measurements
Based on the elastic mechanics theory,a dimensionless mathematical model for the stress dis-tribution in the adjacent rock of the roadway was established to investigate the reasonable depth of the borehole for in-situ stress measurement.The boundary range of the original rock stress in the surrounding rock of the roadway was analyzed under different lateral pressure coefficients and error levels.By numer-ical simulation the stress distribution in the surrounding rock with different roadway widths and heights were studied,revealing the relationship between the depth of the original rock stress boundary in the roadway surrounding rock and the roadway size.The findings validated the appropriate depth of boreholes for in-situ stress measurements on site.The results indicated that the stress in the surrounding rock of the roadway is related to the dimensionless radius R and lateral pressure coefficient of the roadway λ;the influence range of roadway excavation is 3-5 times the roadway radius;when λ＜1,the boundary of the stress influence range of the surrounding rock of the roadway is an ellipse with the long axis parallel to the horizontal axis passing through the center of the roadway;when λ＞1,the boundary of the influence area is an ellipse with a long axis parallel to the vertical axis passing through the center of the roadway;the value,|λ-1|,is larger,the greater the ratio of the long axis to the short axis is;the depth of the in-situ stress measurement borehole should be 1-2 times the width of the roadway when the borehole is on the vertical roadway side;however,when the borehole is vertical to the roof of the roadway,the depth should be 1.5-2.5 times the width of the roadway;the depth of the original rock stress boundary in the surrounding rock also increases with the increase of roadway;the influence of roadway width on the depth of original rock stress is significantly pronounced than that of roadway height.Overall,twice the width of the roadway can be used as the minimum depth limit of the borehole depth for in-situ stress measurements.
万方数据
维普
