To study the effects of loading paths and stress states on rock strength and deformation, marble specimens were axially compressed to various displacements under a confining pressure (CP) firstly, and then the damaged...To study the effects of loading paths and stress states on rock strength and deformation, marble specimens were axially compressed to various displacements under a confining pressure (CP) firstly, and then the damaged specimens were recompressed under another CP. The bearing capacity of a marble specimen depends merely on CP at the stage of ductile deformation, and it has no relation with the loading history when CP keeps constant or increases. However, the damaged specimen turns into brittle when it is recompressed uniaxially or at a lower CP, and the Young’s modulus and strength are lower than those of a dense specimen. The increasing ratio of triaxial strength to CP has a close relation with the areas of fissures in the damaged specimens but not the internal friction angle. Material strength and bearing capacity are two different conceptions for rocks. Material strength decreases continually as the plastic deformation increases; however, the bearing capacity is determined by both the stress state and the material strength.展开更多
This work is realized in the context of valorizing natural and local resources, in particular, luffa plant fruit (luffa sponge). The raw fibers of the luffa sponge have a short lifetime. Hence, when they are chemicall...This work is realized in the context of valorizing natural and local resources, in particular, luffa plant fruit (luffa sponge). The raw fibers of the luffa sponge have a short lifetime. Hence, when they are chemically treated, it constitutes a solution is prepared to limit their degradation in the long term and to improve their mechanical characteristics. Therefore, this paper studies the effect of the chemical treatment on the mechanical properties of the luffa sponge’s fibers (fibers of luffa Sponge). The chemical process consists of dipping a brunch of luffa in various concentrations of sodium hydroxide (NaOH) at different time intervals and at different temperature conditions. The luffa sponge’s fibers were mechanical. Characterized before and after the treatment, mechanically (micro traction test). It has been shown that an optimum of 61% increase in mechanical properties (tensile strength) has been reached in the following conditions: treatment with 1% concentration for 90 min at 50°C.展开更多
In order to investigate the time-dependent behaviors of deep hard rocks in the diversion tunnel of Jinping II hydropower station, uniaxial creep tests were carried out by using the triaxial testing machine RC-2000. Th...In order to investigate the time-dependent behaviors of deep hard rocks in the diversion tunnel of Jinping II hydropower station, uniaxial creep tests were carried out by using the triaxial testing machine RC-2000. The axial compressive load was applied step by step and each creep stage was kept for over several days. Test results show that： （1） The lateral deformation of rock specimens is 2-3 times the axial compressive deformation and accelerates drastically before damage, which may be employed as an indicator to predict the excavation-induced instability of rocks. （2） The resultant deformation changes from compression to expansion when the Poisson＇s ratio is larger than 0.5, indicating the starting point of damage. （3） In the step-loading stages, the Poisson＇s ratio approximately remains constant; under constantly imposed load, the Poisson＇s ratio changes with elapsed time, growing continuously before the specimen is damaged. （4） When the applied load reaches a certain threshold value, the rock deteriorates with time, and the strength of rocks approximately has a negative exponent relation with time. （5） The failure modes of the deep marble are different in long- and short-term loading conditions. Under the condition of short-term loading, the specimen presents a mode of tensile failure; while under the condition of long-term loading, the specimen presents a mode of shear failure, followed by tensile failure.展开更多
Two-order morphology of rock joints named as waviness and unevenness can be separated by morphology classification method,which plays a decisive role in the evolution of shear stress during the shear test.The joint mo...Two-order morphology of rock joints named as waviness and unevenness can be separated by morphology classification method,which plays a decisive role in the evolution of shear stress during the shear test.The joint morphology is obtained by using 3D printing and 3D laser scanning techniques and the joint model samples in two-order morphology are produced by cement mortar.Then,shear tests are performed under different normal loads.Results shows that the waviness is dominant in the total morphology during the shear test,and the shear contribution of unevenness mainly occurs in the climbing phase of shearing process.Comparing the failure modes of two-order morphology,waviness mainly embodies shear dilation characteristics and unevenness mainly shows shear wear characteristics.Based on this,a quantitative parameter is proposed to represent the ratio of the peak shear strength of the two-order morphology to that of total morphology.The functional relationship between the peak shear strength of total and two-order morphologies is determined,providing a theoretical method for further in-depth study on the shear strength of the interaction with two-order morphology of rock joints.展开更多
The effect of mechanical strength of the dispersed particle gel(DPG)on its macro plugging performance is significant,however,little study has been reported.In this paper,DPG particles with different mechanical strengt...The effect of mechanical strength of the dispersed particle gel(DPG)on its macro plugging performance is significant,however,little study has been reported.In this paper,DPG particles with different mechanical strengths were obtained by mechanical shearing of bulk gels prepared with different formula.Young’s moduli of DPG particles on the micro and nano scales were measured by atomic force microscope for the first time.The mapping relationship among the formula of bulk gel,the Young’s moduli of the DPG particles and the final plugging performance were established.The results showed that when the Young’s moduli of the DPG particles increased from 82 to 328 Pa,the plugging rate increased significantly from 91.46%to 97.10%due to the distinctly enhanced stacking density and strength at this range.While when the Young’s moduli of the DPG particles surpassed 328 Pa,the further increase of plugging rate with the Young’s moduli of the DPG particles became insignificant.These results indicated that the improvement of plugging rate was more efficient by adjusting the Young’s moduli of the DPG particles within certain ranges,providing guidance for improving the macroscopic application properties of DPG systems in reservoir heterogeneity regulation.展开更多
基金Supported by the National Natural Science Foundation of China (10572047)
文摘To study the effects of loading paths and stress states on rock strength and deformation, marble specimens were axially compressed to various displacements under a confining pressure (CP) firstly, and then the damaged specimens were recompressed under another CP. The bearing capacity of a marble specimen depends merely on CP at the stage of ductile deformation, and it has no relation with the loading history when CP keeps constant or increases. However, the damaged specimen turns into brittle when it is recompressed uniaxially or at a lower CP, and the Young’s modulus and strength are lower than those of a dense specimen. The increasing ratio of triaxial strength to CP has a close relation with the areas of fissures in the damaged specimens but not the internal friction angle. Material strength and bearing capacity are two different conceptions for rocks. Material strength decreases continually as the plastic deformation increases; however, the bearing capacity is determined by both the stress state and the material strength.
文摘This work is realized in the context of valorizing natural and local resources, in particular, luffa plant fruit (luffa sponge). The raw fibers of the luffa sponge have a short lifetime. Hence, when they are chemically treated, it constitutes a solution is prepared to limit their degradation in the long term and to improve their mechanical characteristics. Therefore, this paper studies the effect of the chemical treatment on the mechanical properties of the luffa sponge’s fibers (fibers of luffa Sponge). The chemical process consists of dipping a brunch of luffa in various concentrations of sodium hydroxide (NaOH) at different time intervals and at different temperature conditions. The luffa sponge’s fibers were mechanical. Characterized before and after the treatment, mechanically (micro traction test). It has been shown that an optimum of 61% increase in mechanical properties (tensile strength) has been reached in the following conditions: treatment with 1% concentration for 90 min at 50°C.
基金Supported by the National Natural Science Foundation of China(50909092)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences (Z000802)the Natural Science Foundation of Hubei Province (2009CDB120)
文摘In order to investigate the time-dependent behaviors of deep hard rocks in the diversion tunnel of Jinping II hydropower station, uniaxial creep tests were carried out by using the triaxial testing machine RC-2000. The axial compressive load was applied step by step and each creep stage was kept for over several days. Test results show that： （1） The lateral deformation of rock specimens is 2-3 times the axial compressive deformation and accelerates drastically before damage, which may be employed as an indicator to predict the excavation-induced instability of rocks. （2） The resultant deformation changes from compression to expansion when the Poisson＇s ratio is larger than 0.5, indicating the starting point of damage. （3） In the step-loading stages, the Poisson＇s ratio approximately remains constant; under constantly imposed load, the Poisson＇s ratio changes with elapsed time, growing continuously before the specimen is damaged. （4） When the applied load reaches a certain threshold value, the rock deteriorates with time, and the strength of rocks approximately has a negative exponent relation with time. （5） The failure modes of the deep marble are different in long- and short-term loading conditions. Under the condition of short-term loading, the specimen presents a mode of tensile failure; while under the condition of long-term loading, the specimen presents a mode of shear failure, followed by tensile failure.
基金funded by National Natural Science Foundation of China(Grant Nos.42272333 and 42277147)。
文摘Two-order morphology of rock joints named as waviness and unevenness can be separated by morphology classification method,which plays a decisive role in the evolution of shear stress during the shear test.The joint morphology is obtained by using 3D printing and 3D laser scanning techniques and the joint model samples in two-order morphology are produced by cement mortar.Then,shear tests are performed under different normal loads.Results shows that the waviness is dominant in the total morphology during the shear test,and the shear contribution of unevenness mainly occurs in the climbing phase of shearing process.Comparing the failure modes of two-order morphology,waviness mainly embodies shear dilation characteristics and unevenness mainly shows shear wear characteristics.Based on this,a quantitative parameter is proposed to represent the ratio of the peak shear strength of the two-order morphology to that of total morphology.The functional relationship between the peak shear strength of total and two-order morphologies is determined,providing a theoretical method for further in-depth study on the shear strength of the interaction with two-order morphology of rock joints.
基金financially supported by the National Key Research and Development Program of China(No.2019YFA0708700)National Natural Science Foundation of China(52174054,51804326)Shandong Provincial Natural Science Foundation(ZR2019BEE046)
文摘The effect of mechanical strength of the dispersed particle gel(DPG)on its macro plugging performance is significant,however,little study has been reported.In this paper,DPG particles with different mechanical strengths were obtained by mechanical shearing of bulk gels prepared with different formula.Young’s moduli of DPG particles on the micro and nano scales were measured by atomic force microscope for the first time.The mapping relationship among the formula of bulk gel,the Young’s moduli of the DPG particles and the final plugging performance were established.The results showed that when the Young’s moduli of the DPG particles increased from 82 to 328 Pa,the plugging rate increased significantly from 91.46%to 97.10%due to the distinctly enhanced stacking density and strength at this range.While when the Young’s moduli of the DPG particles surpassed 328 Pa,the further increase of plugging rate with the Young’s moduli of the DPG particles became insignificant.These results indicated that the improvement of plugging rate was more efficient by adjusting the Young’s moduli of the DPG particles within certain ranges,providing guidance for improving the macroscopic application properties of DPG systems in reservoir heterogeneity regulation.
