Osmotic water alters the physicochemical properties and internal structures of limestone.This issue is particularly critical in tunnel construction across mountainous regions with aquifers,where pressurized groundwate...Osmotic water alters the physicochemical properties and internal structures of limestone.This issue is particularly critical in tunnel construction across mountainous regions with aquifers,where pressurized groundwater can destabilize the limestone-based surrounding rock.Thus,systematic research into the physicochemical properties and pore structure changes in the limestone under pressurized water is essential.Additionally,it is essential to develop an interpretable mathematical model to accurately depict how pressurized osmotic water weakens limestone.In this research,a specialized device was designed to simulate the process of osmotic laminar flow within limestone.Then,four main tests were conducted:mass loss,acoustic emission(AE),mercury intrusion porosimetry(MIP),and fluorescence analysis.Experimental results gained from tests led to the development of a“Particle-pore throat-water film”model.Proposed model explains water-induced physicochemical and pore changes in limestone under osmotic pressure and reveals evolutionary mechanisms as pressure increases.Based on experimental results and model,we found that osmotic pressure not only alters limestone composition but also affects pore throats larger than 0.1μm.Furthermore,osmotic pressure expands pore throats,enhancing pore structure uniformity,interconnectivity,and permeability.These effects are observed at a threshold of 7.5 MPa,where cohesive forces within the mineral lattice are surpassed,leading to the breakdown of erosion-resistant layer and a significant increase in hydrochemical erosion.展开更多
In view of the effect of fissure water in fractured rock mass on the strength of rock mass in engineering projects, we pre-pared specimens of cement mortar to simulate saturated rock mass with continuous fractures of ...In view of the effect of fissure water in fractured rock mass on the strength of rock mass in engineering projects, we pre-pared specimens of cement mortar to simulate saturated rock mass with continuous fractures of different slope angles. By exerting static and dynamic loads on the specimens, the mechanical characteristics of rock mass with fissure water under these loads can be analyzed. Our experimental results indicate that the static compressive strength of saturated fractured rock mass is related to the slope angle. The lowest compressive strength of fractured rock mass occurs when the slope angle is 45°, while the highest strength occurs when the specimen has no fractures. Fissure water can weaken the strength of rock mass. The softening coefficient does not vary with the slope angle and type of load. The hydrodynamic pressure of fractured rock mass gradually increases with an increase in dynamic load. For a 0° slope angle, the hydrodynamic pressure reaches its highest level. When the slope angle is 90°, the hydro-dynamic pressure is the lowest.展开更多
It is important to study the dilatancy property of water-saturated rock for understanding the engineering behavior of loaded rock mass. This study carried out the uniaxial and triaxial compressive experiments on the w...It is important to study the dilatancy property of water-saturated rock for understanding the engineering behavior of loaded rock mass. This study carried out the uniaxial and triaxial compressive experiments on the water-saturated red sandstone, analyzed the influences of confining pressure and pore pressure on dilatancy property of water-saturated rock, and discussed the reasonable basis of the stress of dilatancy onset as a strength design parameter of rock engineering, finally established the prediction model of the stress of dilatancy onset under the impacts of confining pressure and pore pressure. The results show that the strength parameters(the stress of dilatancy onset and peak strength) and deformation parameters(axial strain and circumferential strain) of water-saturated sandstone increase with the confining pressure, and the relations can be fitted with a positive linear function. The cohesion and internal friction angle obtained from the stress of dilatancy onset decrease by 11.57% and 7.33%, respectively, when compared with those obtained from the peak strength. The strength parameters and deformation parameters of water-saturated sandstone decrease basically with the increase of pore pressure, in which the relations between strength parameters or axial strain and pore pressure can be fitted with a negative linear function. However, the relation between the peak circumferential strain and the pore pressure should be characterized by a negative exponential function, and the circumferential strain at dilatancy onset isn't affected by the pore pressure.展开更多
In this paper, the mechanical response of saturated geological rock under tidal force is explored by poroelastic theory. First, we use the free energy formula of saturated rock under a tidal force to study the relatio...In this paper, the mechanical response of saturated geological rock under tidal force is explored by poroelastic theory. First, we use the free energy formula of saturated rock under a tidal force to study the relationships of pore pressure with stress, and stress with strain. Then we analyze the relationship between rock strain and tidal potential by the equilibrium differential equations of saturated rock under tidal force. Finally, we derive the physical relationship between the two parameters （pore pressure and tidal mean stress） of saturated rock and tidal potential. The relationship shows that：pore pressure is directly proportional with tidal potential, but tidal mean stress of saturated rock is inversely proportional with tidal potential. The ratio coefficient is related not only to the Lame coefficients of rock skeletons, but also to the Blot modulus. By using this model to analyze observational well water level of C-18 well which locates in Huili, Sichuan Province, the well level response coefficient （D） was estimated. This way, we derive the Skempton coefficient （B）, the coefficient A and C which refer to the response coefficients of pore pressure and tidal stress to tidal potential respectively. Then we compare the differences among each coefficient in coupling and uncoupling conditions. It shows that for saturated rocks, the response of stress and pore pressure to earth tides is a product of coupling, and it is necessary to take into account the coupling effect when we study the mechanical response. The model will provide the basis not only for the study of mechanics and hydrodynamics of well-confined aquifer systems, and the mechanics of faulting under tidal force, but also for quantitative research of the triggering mechanism of tidal forces.展开更多
A test system was developed for measuring the pore pressure in porous media, and a new model was devised for the pore pressure testing in both saturated and unsaturated rock-soil. Laboratory experiments were carried o...A test system was developed for measuring the pore pressure in porous media, and a new model was devised for the pore pressure testing in both saturated and unsaturated rock-soil. Laboratory experiments were carried out to determine the pore pressure during water level fluctuation. The variations of transient pore pressure vs. time at different locations of the simulated rock-soil system were acquired and processed, and meanwhile the deformation and failure of the model are observed. The experiment results show that whether the porous media are saturated or not, the transient pore pressure is mainly dependent on the water level fluctuation, and coupled with the variation of the stress field.展开更多
利用MTS815 Flex Test GT岩石力学试验系统,经过岩体受力状态模拟、无水压岩体力学特性测试、水岩耦合试验等几个阶段试验,对砂板岩岩体力学特性的高空隙水压效应进行了试验研究。结果表明:砂板岩岩体强度与变形性能随水压升高而降低,...利用MTS815 Flex Test GT岩石力学试验系统,经过岩体受力状态模拟、无水压岩体力学特性测试、水岩耦合试验等几个阶段试验,对砂板岩岩体力学特性的高空隙水压效应进行了试验研究。结果表明:砂板岩岩体强度与变形性能随水压升高而降低,其中水压对黏聚力c的影响最大,对内摩擦角φ的影响甚微,对变形模量的影响居于二者之间。随着水压升高,岩体的黏聚力c急剧下降,当水压较高时,岩体可能完全丧失黏聚力;随着水压升高,变形模量E50和E0均有降低,两个参数的变化梯度相差不大。这些成果揭示了砂板岩岩体力学特性的高空隙水压力效应,并建立了主要力学参数预测模型,成果对于解决工程实际问题具有重要的参考价值。展开更多
基金funded by the National Key R&D Program of China(2023YFC3806800).
文摘Osmotic water alters the physicochemical properties and internal structures of limestone.This issue is particularly critical in tunnel construction across mountainous regions with aquifers,where pressurized groundwater can destabilize the limestone-based surrounding rock.Thus,systematic research into the physicochemical properties and pore structure changes in the limestone under pressurized water is essential.Additionally,it is essential to develop an interpretable mathematical model to accurately depict how pressurized osmotic water weakens limestone.In this research,a specialized device was designed to simulate the process of osmotic laminar flow within limestone.Then,four main tests were conducted:mass loss,acoustic emission(AE),mercury intrusion porosimetry(MIP),and fluorescence analysis.Experimental results gained from tests led to the development of a“Particle-pore throat-water film”model.Proposed model explains water-induced physicochemical and pore changes in limestone under osmotic pressure and reveals evolutionary mechanisms as pressure increases.Based on experimental results and model,we found that osmotic pressure not only alters limestone composition but also affects pore throats larger than 0.1μm.Furthermore,osmotic pressure expands pore throats,enhancing pore structure uniformity,interconnectivity,and permeability.These effects are observed at a threshold of 7.5 MPa,where cohesive forces within the mineral lattice are surpassed,leading to the breakdown of erosion-resistant layer and a significant increase in hydrochemical erosion.
基金support for this work, provided by the National Natural Science Foundation of China (No50534040)
文摘In view of the effect of fissure water in fractured rock mass on the strength of rock mass in engineering projects, we pre-pared specimens of cement mortar to simulate saturated rock mass with continuous fractures of different slope angles. By exerting static and dynamic loads on the specimens, the mechanical characteristics of rock mass with fissure water under these loads can be analyzed. Our experimental results indicate that the static compressive strength of saturated fractured rock mass is related to the slope angle. The lowest compressive strength of fractured rock mass occurs when the slope angle is 45°, while the highest strength occurs when the specimen has no fractures. Fissure water can weaken the strength of rock mass. The softening coefficient does not vary with the slope angle and type of load. The hydrodynamic pressure of fractured rock mass gradually increases with an increase in dynamic load. For a 0° slope angle, the hydrodynamic pressure reaches its highest level. When the slope angle is 90°, the hydro-dynamic pressure is the lowest.
基金supported by the National Natural Science Foundation of China (Nos. 51404266 and 11502229)the National Program on Key Basic Research Project of China (No. 2013CB227900)
文摘It is important to study the dilatancy property of water-saturated rock for understanding the engineering behavior of loaded rock mass. This study carried out the uniaxial and triaxial compressive experiments on the water-saturated red sandstone, analyzed the influences of confining pressure and pore pressure on dilatancy property of water-saturated rock, and discussed the reasonable basis of the stress of dilatancy onset as a strength design parameter of rock engineering, finally established the prediction model of the stress of dilatancy onset under the impacts of confining pressure and pore pressure. The results show that the strength parameters(the stress of dilatancy onset and peak strength) and deformation parameters(axial strain and circumferential strain) of water-saturated sandstone increase with the confining pressure, and the relations can be fitted with a positive linear function. The cohesion and internal friction angle obtained from the stress of dilatancy onset decrease by 11.57% and 7.33%, respectively, when compared with those obtained from the peak strength. The strength parameters and deformation parameters of water-saturated sandstone decrease basically with the increase of pore pressure, in which the relations between strength parameters or axial strain and pore pressure can be fitted with a negative linear function. However, the relation between the peak circumferential strain and the pore pressure should be characterized by a negative exponential function, and the circumferential strain at dilatancy onset isn't affected by the pore pressure.
基金supported by R&D Special Fund for Public Welfare Industry of Ministry of Science and Technology(200808055 and 200808079),the People's Republic of ChinaScience Research Plan Project of Hebei Province(Z2009104)
文摘In this paper, the mechanical response of saturated geological rock under tidal force is explored by poroelastic theory. First, we use the free energy formula of saturated rock under a tidal force to study the relationships of pore pressure with stress, and stress with strain. Then we analyze the relationship between rock strain and tidal potential by the equilibrium differential equations of saturated rock under tidal force. Finally, we derive the physical relationship between the two parameters （pore pressure and tidal mean stress） of saturated rock and tidal potential. The relationship shows that：pore pressure is directly proportional with tidal potential, but tidal mean stress of saturated rock is inversely proportional with tidal potential. The ratio coefficient is related not only to the Lame coefficients of rock skeletons, but also to the Blot modulus. By using this model to analyze observational well water level of C-18 well which locates in Huili, Sichuan Province, the well level response coefficient （D） was estimated. This way, we derive the Skempton coefficient （B）, the coefficient A and C which refer to the response coefficients of pore pressure and tidal stress to tidal potential respectively. Then we compare the differences among each coefficient in coupling and uncoupling conditions. It shows that for saturated rocks, the response of stress and pore pressure to earth tides is a product of coupling, and it is necessary to take into account the coupling effect when we study the mechanical response. The model will provide the basis not only for the study of mechanics and hydrodynamics of well-confined aquifer systems, and the mechanics of faulting under tidal force, but also for quantitative research of the triggering mechanism of tidal forces.
文摘A test system was developed for measuring the pore pressure in porous media, and a new model was devised for the pore pressure testing in both saturated and unsaturated rock-soil. Laboratory experiments were carried out to determine the pore pressure during water level fluctuation. The variations of transient pore pressure vs. time at different locations of the simulated rock-soil system were acquired and processed, and meanwhile the deformation and failure of the model are observed. The experiment results show that whether the porous media are saturated or not, the transient pore pressure is mainly dependent on the water level fluctuation, and coupled with the variation of the stress field.
文摘利用MTS815 Flex Test GT岩石力学试验系统,经过岩体受力状态模拟、无水压岩体力学特性测试、水岩耦合试验等几个阶段试验,对砂板岩岩体力学特性的高空隙水压效应进行了试验研究。结果表明:砂板岩岩体强度与变形性能随水压升高而降低,其中水压对黏聚力c的影响最大,对内摩擦角φ的影响甚微,对变形模量的影响居于二者之间。随着水压升高,岩体的黏聚力c急剧下降,当水压较高时,岩体可能完全丧失黏聚力;随着水压升高,变形模量E50和E0均有降低,两个参数的变化梯度相差不大。这些成果揭示了砂板岩岩体力学特性的高空隙水压力效应,并建立了主要力学参数预测模型,成果对于解决工程实际问题具有重要的参考价值。
