When the geological environment of rock masses is disturbed,numerous non-persisting open joints can appear within it.It is crucial to investigate the effect of open joints on the mechanical properties of rock mass.How...When the geological environment of rock masses is disturbed,numerous non-persisting open joints can appear within it.It is crucial to investigate the effect of open joints on the mechanical properties of rock mass.However,it has been challenging to generate realistic open joints in traditional experimental tests and numerical simulations.This paper presents a novel solution to solve the problem.By utilizing the stochastic distribution of joints and an enhanced-fractal interpolation system(IFS)method,rough curves with any orientation can be generated.The Douglas-Peucker algorithm is then applied to simplify these curves by removing unnecessary points while preserving their fundamental shape.Subsequently,open joints are created by connecting points that move to both sides of rough curves based on the aperture distribution.Mesh modeling is performed to construct the final mesh model.Finally,the RB-DEM method is applied to transform the mesh model into a discrete element model containing geometric information about these open joints.Furthermore,this study explores the impacts of rough open joint orientation,aperture,and number on rock fracture mechanics.This method provides a realistic and effective approach for modeling and simulating these non-persisting open joints.展开更多
Effects of two important factors on earthquake response of high arch dams are considered and combined into one program.These tactors are:effects of radiation damping of the infinite canyon and local non-linearity of t...Effects of two important factors on earthquake response of high arch dams are considered and combined into one program.These tactors are:effects of radiation damping of the infinite canyon and local non-linearity of the contraction joint opening between the dam monoliths.For modeling of rock canyon,the discrete parameters are obtained based on a curve fitting, thus allowing the nonlinear dam system to be solved in the time domain.The earthquake uniform tree-field input at the dam-canyon interface is used.An engineering example is given to demonstrate the significant effects of the radiation damping on the structure response.展开更多
The stability of underground excavations is influenced by discontinuities interspaced in surrounding rock masses as well as the stress condition. In this work, a numerical study was undertaken on the failure behavior ...The stability of underground excavations is influenced by discontinuities interspaced in surrounding rock masses as well as the stress condition. In this work, a numerical study was undertaken on the failure behavior around a circular opening in a rock mass having non-persistent open joints using PFC software package. A parallel-bond stress corrosion(PSC) approach was incorporated to drive the failure of rock mass around the circular opening, such that the whole progressive failure process after excavation was reproduced. Based on the determined micro parameters for intact material and joint segments, the failure process around the circular opening agrees very well with that obtained through laboratory experiment. A subsequent parametric study was then carried out to look into the influence of lateral pressure coefficient, joint dip angle and joint persistency on the failure pattern and crack evolution of the rock mass around the circular opening. Three failure patterns identified are step path failure, planar failure and rotation failure depending on the lateral pressure coefficient. Moreover, the increment of joint dip angle and joint persistency aggravates the rock mass failure around the opening. This study offers guideline on stability estimation of underground excavations.展开更多
Pre-existing discontinuities change the mechanical properties of rock masses,and further influence failure behavior around an underground opening.In present study,the failure behavior in both Inner and Outer zones aro...Pre-existing discontinuities change the mechanical properties of rock masses,and further influence failure behavior around an underground opening.In present study,the failure behavior in both Inner and Outer zones around a circular opening in a non-persistently jointed rock mass under biaxial compression was investigated through numerical simulations.First,the micro parameters of the PFC^(3D) model were carefully calibrated using the macro mechanical properties determined in physical experiments implemented on jointed rock models.Then,a parametrical study was undertaken of the effect of stress condition,joint dip angle and joint persistency.Under low initial stress,the confining stress improves the mechanical behavior of the surrounding rock masses;while under high initial stress,the surrounding rock mass failed immediately following excavation.At small dip angles the cracks around the circular opening developed generally outwards in a step-path failure pattern;whereas,at high dip angles the surrounding rock mass failed in an instantaneous intact rock failure pattern.Moreover,the stability of the rock mass around the circular opening deteriorated significantly with increasing joint persistency.展开更多
Temporomandibular disorders (TMD) negatively affect quality of life, causing pain and restricted jaw movements. This study evaluates the effectiveness of Transcutaneous Electrical Nerve Stimulation (TENS) on TMD patie...Temporomandibular disorders (TMD) negatively affect quality of life, causing pain and restricted jaw movements. This study evaluates the effectiveness of Transcutaneous Electrical Nerve Stimulation (TENS) on TMD patients before orthodontic treatment at the Juarez Autonomous University of Tabasco. A quantitative, quasi-experimental study was conducted with 30 patients who met the inclusion criteria: aged 18 to 65 years, with TMJ pain symptoms, diagnosed with temporomandibular disorders using the Helkimo index, and who had provided informed consent for the study. The range of mandibular movement and the Visual Analog Scale (VAS) were measured to record values before therapy. The electrodes of the TENS therapy were positioned on both sides of the jaw in the preauricular area and the masseter muscle, the therapy was administered for 40 minutes, utilizing a frequency of 2 - 4 Hz and a pulse duration of 300 microseconds. Following this, the range of mandibular movement and the VAS were reassessed to evaluate the outcomes., significantly improved maximum mouth opening (37.7 ± 6.4 mm to 44.6 ± 5.88 mm), right laterality (3.86 ± 1.57 mm to 5.43 ± 1.21 mm), left laterality (3.13 ± 1.63 mm to 4.53 ± 1.61 mm), protrusion (4.01 ± 1.7 mm to 5.36 ± 1.32 mm), and pain perception (4.56 ± 2.045 to 2.03 ± 1.5) (P < 0.01). TENS therapy enhances mandibular movement and reduces pain, making it a well-tolerated, non-invasive complementary treatment for TMD.展开更多
基金supported by the National Key R&D Program of China (2018YFC0407004)the Fundamental Research Funds for the Central Universities (Nos.B200201059,2021FZZX001-14)the National Natural Science Foundation of China (Grant No.51709089)and 111 Project.
文摘When the geological environment of rock masses is disturbed,numerous non-persisting open joints can appear within it.It is crucial to investigate the effect of open joints on the mechanical properties of rock mass.However,it has been challenging to generate realistic open joints in traditional experimental tests and numerical simulations.This paper presents a novel solution to solve the problem.By utilizing the stochastic distribution of joints and an enhanced-fractal interpolation system(IFS)method,rough curves with any orientation can be generated.The Douglas-Peucker algorithm is then applied to simplify these curves by removing unnecessary points while preserving their fundamental shape.Subsequently,open joints are created by connecting points that move to both sides of rough curves based on the aperture distribution.Mesh modeling is performed to construct the final mesh model.Finally,the RB-DEM method is applied to transform the mesh model into a discrete element model containing geometric information about these open joints.Furthermore,this study explores the impacts of rough open joint orientation,aperture,and number on rock fracture mechanics.This method provides a realistic and effective approach for modeling and simulating these non-persisting open joints.
文摘Effects of two important factors on earthquake response of high arch dams are considered and combined into one program.These tactors are:effects of radiation damping of the infinite canyon and local non-linearity of the contraction joint opening between the dam monoliths.For modeling of rock canyon,the discrete parameters are obtained based on a curve fitting, thus allowing the nonlinear dam system to be solved in the time domain.The earthquake uniform tree-field input at the dam-canyon interface is used.An engineering example is given to demonstrate the significant effects of the radiation damping on the structure response.
基金Project(2013CB036003)supported by the National Basic Research Program of ChinaProjects(51374198,51134001,51404255)supported by the National Natural Science Foundation of ChinaProject(BK20150005)supported by the Natural Science Foundation of Jiangsu Province for Distinguished Youth Scholar,China
文摘The stability of underground excavations is influenced by discontinuities interspaced in surrounding rock masses as well as the stress condition. In this work, a numerical study was undertaken on the failure behavior around a circular opening in a rock mass having non-persistent open joints using PFC software package. A parallel-bond stress corrosion(PSC) approach was incorporated to drive the failure of rock mass around the circular opening, such that the whole progressive failure process after excavation was reproduced. Based on the determined micro parameters for intact material and joint segments, the failure process around the circular opening agrees very well with that obtained through laboratory experiment. A subsequent parametric study was then carried out to look into the influence of lateral pressure coefficient, joint dip angle and joint persistency on the failure pattern and crack evolution of the rock mass around the circular opening. Three failure patterns identified are step path failure, planar failure and rotation failure depending on the lateral pressure coefficient. Moreover, the increment of joint dip angle and joint persistency aggravates the rock mass failure around the opening. This study offers guideline on stability estimation of underground excavations.
基金supported by the National Basic Research Program of China (No.2013CB036003)the Graduate Research and Innovation Program of Jiangsu Province (No.CXLX13_943)
文摘Pre-existing discontinuities change the mechanical properties of rock masses,and further influence failure behavior around an underground opening.In present study,the failure behavior in both Inner and Outer zones around a circular opening in a non-persistently jointed rock mass under biaxial compression was investigated through numerical simulations.First,the micro parameters of the PFC^(3D) model were carefully calibrated using the macro mechanical properties determined in physical experiments implemented on jointed rock models.Then,a parametrical study was undertaken of the effect of stress condition,joint dip angle and joint persistency.Under low initial stress,the confining stress improves the mechanical behavior of the surrounding rock masses;while under high initial stress,the surrounding rock mass failed immediately following excavation.At small dip angles the cracks around the circular opening developed generally outwards in a step-path failure pattern;whereas,at high dip angles the surrounding rock mass failed in an instantaneous intact rock failure pattern.Moreover,the stability of the rock mass around the circular opening deteriorated significantly with increasing joint persistency.
文摘Temporomandibular disorders (TMD) negatively affect quality of life, causing pain and restricted jaw movements. This study evaluates the effectiveness of Transcutaneous Electrical Nerve Stimulation (TENS) on TMD patients before orthodontic treatment at the Juarez Autonomous University of Tabasco. A quantitative, quasi-experimental study was conducted with 30 patients who met the inclusion criteria: aged 18 to 65 years, with TMJ pain symptoms, diagnosed with temporomandibular disorders using the Helkimo index, and who had provided informed consent for the study. The range of mandibular movement and the Visual Analog Scale (VAS) were measured to record values before therapy. The electrodes of the TENS therapy were positioned on both sides of the jaw in the preauricular area and the masseter muscle, the therapy was administered for 40 minutes, utilizing a frequency of 2 - 4 Hz and a pulse duration of 300 microseconds. Following this, the range of mandibular movement and the VAS were reassessed to evaluate the outcomes., significantly improved maximum mouth opening (37.7 ± 6.4 mm to 44.6 ± 5.88 mm), right laterality (3.86 ± 1.57 mm to 5.43 ± 1.21 mm), left laterality (3.13 ± 1.63 mm to 4.53 ± 1.61 mm), protrusion (4.01 ± 1.7 mm to 5.36 ± 1.32 mm), and pain perception (4.56 ± 2.045 to 2.03 ± 1.5) (P < 0.01). TENS therapy enhances mandibular movement and reduces pain, making it a well-tolerated, non-invasive complementary treatment for TMD.
