In-situ stress is a key parameter for underground mine design and rock stability analysis.The borehole overcoring technique is widely used for in-situ stress measurement,but the rheological recovery deformation of roc...In-situ stress is a key parameter for underground mine design and rock stability analysis.The borehole overcoring technique is widely used for in-situ stress measurement,but the rheological recovery deformation of rocks after stress relief introduces errors.To improve accuracy,this study proposes an in-situ stress solution theory that incorporates time-dependent stress relief effects.Triaxial stepwise loadingunloading rheological tests on granite and siltstone established quantitative relationships between instantaneous elastic recovery and viscoelastic recovery under different stress levels,confirming their impact on measurement accuracy.By integrating a dual-class elastic deformation recovery model,an improved in-situ stress solution theory was derived.Additionally,accounting for the nonlinear characteristics of rock masses,a determination method for time-dependent nonlinear mechanical parameters was proposed.Based on the CSIRO hollow inclusion strain cell,time-dependent strain correction equations and long-term confining pressure calibration equations were formulated.Finally,the proposed theory was successfully applied at one iron mine(736 m depth)in Xinjiang,China,and one coal mine(510 m depth)in Ningxia,China.Compared to classical theory,the calculated mean stress values showed accuracy improvements of 6.0%and 9.4%,respectively,validating the applicability and reliability of the proposed theory.展开更多
The coal dynamic characteristic stress identification under dynamic load is important for guiding underground mineral mining and predicting underground dynamic disasters.In this article,the dynamic compression test of...The coal dynamic characteristic stress identification under dynamic load is important for guiding underground mineral mining and predicting underground dynamic disasters.In this article,the dynamic compression test of anthracite under five strain rates is carried out,the evolution law of three kinds of crack characteristic stress is analyzed,and a prediction model of the crack characteristic stress threshold considering the strain rate effect is established.Then,the rationality of crack characteristic stress under dynamic loading is discussed from the damage evolution standpoint,and the crack extension response mechanism during dynamic compression of anthracite is discussed.The result shows that the crack characteristic stress threshold is significantly influenced by the strain rate.The three characteristic stress thresholds are positively correlated with the strain rate,but the ratios to the crest stress gradually decrease.The increase in the strain rate strongly contributes to the crack extension behavior of anthracite.In the crack unstable extension phase,because of the increase of the strain rate,anthracite shows more energy dissipation under the same deformation in association with the stress concentration effect and the dynamic strength enhancement effect.The crack propagation rate is increased,the crack propagation path of the section is more complex,and more severe damage occurs before the dynamic failure of anthracite,which leads to even more severe damage.展开更多
基金supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2024ZD1700201)the National Natural Science Foundation of China(Nos.U2034206,51974014 and 51574014)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2024A1515011631)the National Key Research and Development Project of China(No.2022YFC3004601)。
文摘In-situ stress is a key parameter for underground mine design and rock stability analysis.The borehole overcoring technique is widely used for in-situ stress measurement,but the rheological recovery deformation of rocks after stress relief introduces errors.To improve accuracy,this study proposes an in-situ stress solution theory that incorporates time-dependent stress relief effects.Triaxial stepwise loadingunloading rheological tests on granite and siltstone established quantitative relationships between instantaneous elastic recovery and viscoelastic recovery under different stress levels,confirming their impact on measurement accuracy.By integrating a dual-class elastic deformation recovery model,an improved in-situ stress solution theory was derived.Additionally,accounting for the nonlinear characteristics of rock masses,a determination method for time-dependent nonlinear mechanical parameters was proposed.Based on the CSIRO hollow inclusion strain cell,time-dependent strain correction equations and long-term confining pressure calibration equations were formulated.Finally,the proposed theory was successfully applied at one iron mine(736 m depth)in Xinjiang,China,and one coal mine(510 m depth)in Ningxia,China.Compared to classical theory,the calculated mean stress values showed accuracy improvements of 6.0%and 9.4%,respectively,validating the applicability and reliability of the proposed theory.
基金National Natural Science Foundation of China,Grant/Award Numbers:12072363,12372373,51934007,52104234,52174091。
文摘The coal dynamic characteristic stress identification under dynamic load is important for guiding underground mineral mining and predicting underground dynamic disasters.In this article,the dynamic compression test of anthracite under five strain rates is carried out,the evolution law of three kinds of crack characteristic stress is analyzed,and a prediction model of the crack characteristic stress threshold considering the strain rate effect is established.Then,the rationality of crack characteristic stress under dynamic loading is discussed from the damage evolution standpoint,and the crack extension response mechanism during dynamic compression of anthracite is discussed.The result shows that the crack characteristic stress threshold is significantly influenced by the strain rate.The three characteristic stress thresholds are positively correlated with the strain rate,but the ratios to the crest stress gradually decrease.The increase in the strain rate strongly contributes to the crack extension behavior of anthracite.In the crack unstable extension phase,because of the increase of the strain rate,anthracite shows more energy dissipation under the same deformation in association with the stress concentration effect and the dynamic strength enhancement effect.The crack propagation rate is increased,the crack propagation path of the section is more complex,and more severe damage occurs before the dynamic failure of anthracite,which leads to even more severe damage.
