International Journal of Rock Mechanics and Mining Sciences最新文献

{"title":"Charge signals characterizing the influence of bedding angles on shale damage under cyclic loading and unloading","authors":"Long Ren, Baolong Zhu, Jing Li, Liming Qiu","doi":"10.1016/j.ijrmms.2024.106001","DOIUrl":"https://doi.org/10.1016/j.ijrmms.2024.106001","url":null,"abstract":"The role of bedding angle on the mechanic properties and failure modes of shale under cyclic loading and unloading conditions is unclear. This study conducted uniaxial cyclic loading and unloading tests on shales from the Longmaxi Formation with different bedding angles (<ce:italic>θ</ce:italic> = 0°, 22.5°, 45°, 67.5° and 90°), and characterized their damage evolution through both AE and charge signals. Results show that the compressive strengths are higher, and the loading cycles are more in specimens with <ce:italic>θ</ce:italic> = 0° and 90° than those with <ce:italic>θ</ce:italic> = 22.5°, 45° and 67.5° during cyclic loading tests, resulting in a silent period of signaling presented in former but not in latter <ce:italic>θ</ce:italic>. Both AE and charge signals can well reflect the major damages in time-domain analysis, while only charge signals can characterize the minor damages at the silent stages by continuous wavelet transforming into time-frequency plots, leading to their advantages in characterizing the damage evolution in specimens with <ce:italic>θ</ce:italic> = 0° and 90°, but not with <ce:italic>θ</ce:italic> = 22.5°, 45° and 67.5°. These differences can be attributed to their different signal acquirement mechanisms. These findings highlight the effectiveness of charge signals in characterizing the shale damage evolution under loading and unloading conditions.","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"22 1","pages":""},"PeriodicalIF":7.2,"publicationDate":"2024-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A shear strength criterion of rock joints under dynamic normal load","authors":"Qiang Zhang, Qiuxin Gu, Shuchen Li, Hongying Wang, Guilei Han","doi":"10.1016/j.ijrmms.2024.106002","DOIUrl":"https://doi.org/10.1016/j.ijrmms.2024.106002","url":null,"abstract":"The shear strength of rock joints under dynamic normal load (DNL) conditions is quite different from that under constant normal loading (CNL) conditions. However, existing studies seldom involve the shear strength prediction of rock joints under DNL conditions. Therefore, a series of shear tests for rock joints under DNL conditions were carried out. The evolutions of the shear strength parameters, including both cohesion and internal friction angle, with dynamic loading amplitude and frequency were investigated according to the experimental results. A shear strength criterion for rock joints under DNL conditions was developed. The proposed model was verified by comparing the theoretically predicted values with experimental results, both of which showed excellent agreement. Additionally, the strength criterion is utilized to predict the peak shear strength under CNL and new DNL conditions. These prediction results were further validated by experimental methods, which extend the applicability of the proposed strength criterion. This study can provide valuable references for the stability evaluation of rock formation engineering and geological hazard warning under dynamic load disturbance.","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"2 1","pages":""},"PeriodicalIF":7.2,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fully coupled hydro-mechanical–chemical continuum modeling of fluid percolation through rock salt","authors":"Ishmael Dominic Yevugah, Xiang-Zhao Kong, Antoine B. Jacquey, Christopher P. Green, Hartmut M. Holländer, Pooneh Maghoul","doi":"10.1016/j.ijrmms.2024.105985","DOIUrl":"https://doi.org/10.1016/j.ijrmms.2024.105985","url":null,"abstract":"In domal and bedded rock salt geothermal reservoirs, geochemical dissolution of the in-situ rock salt formation can alter fluid transport properties, thus impacting fluid flow. Coupled Hydro-mechanical–chemical (HMC) modeling is a useful tool to evaluate fluid transport through rock salt geothermal systems and to assess their economic potential. Existing continuum-based numerical simulation of fluid transport through rock salt relies on the polyhedral orientation of rock salt crystal boundaries as potential fluid pathways, employing a deformation-dependent permeability model to depict pressure-driven fluid flow through rock salt. However, this numerical approach is exclusively HM-coupled and overlooks the influence of halite dissolution/precipitation on the permeability model. This study extends the deformation-dependent permeability model to account for halite dissolution by adopting a reverse mineral growth approach. Using this extended (HMC-coupled) model, we capture the relevance of geochemical reactions on the response of rock salt formations undergoing pressure-driven fluid percolation. The resulting simulations predict a lower fluid pressure than the HM-coupled scenario, highlighting the impact of halite dissolution on fluid flow through rock salt.","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"75 1","pages":""},"PeriodicalIF":7.2,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelling microwave fracturing of rocks: A continuum-discontinuum numerical approach","authors":"Yinjiang Nie, Yanlong Zheng, Jianchun Li","doi":"10.1016/j.ijrmms.2024.105975","DOIUrl":"https://doi.org/10.1016/j.ijrmms.2024.105975","url":null,"abstract":"Existing numerical models cannot well reproduce the fracturing process and reveal the underlying mechanisms of rocks under microwave irradiation. In this work, the electromagnetic-thermal-mechanical multiphysics is decoupled into microwave-induced heating (continuum-based) and thermally-driven fracturing (discontinuum-based), with temperature serving as the key interlink. The rigid-body spring-subset network (RBSSN) model is proposed to calculate the progressive fracturing of rocks under open-ended microwave irradiation, where the individual contacts between adjacent tetrahedral blocks are disassembled into three hypothetical spring-subsets. To depict failure characteristics of large-scale rocks under microwave irradiation, a variable-sized block model is developed by densifying the rigid-blocks near the irradiation. This electromagnetic-thermal-mechanical decoupling framework effectively captures the microwave fracturing process, revealing that microwave irradiation induces tensile-dominant progressive failure and regionalized deterioration (localized damage and macroscopic radial fissure). The fracturing rate of rocks is time-dependent, progressing through silent, violent and slowdown periods of rupturing with extended exposure time. The reason why high-power microwave is more effective in promoting visible fractures under the identical input energy is analyzed by combining the thermal deformation theory and RBSSN simulation. It is found that, power levels should be kept within reasonable scopes to maximize fracturing effects as excessive power densities lead to initiation of numerous microcracks around the high temperature zone and susceptibility to spalling.","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"21 1","pages":""},"PeriodicalIF":7.2,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of Forchheimer equation coefficients for nonlinear flow through rough-walled fractures during shearing","authors":"Xu Zhu, Guangyao Si, Chengguo Zhang, Yingchun Li, Joung Oh","doi":"10.1016/j.ijrmms.2024.105992","DOIUrl":"https://doi.org/10.1016/j.ijrmms.2024.105992","url":null,"abstract":"The presence of complex geometric morphology of single rough-walled rock fractures and the occurrence of nonlinear flow complicate the fracture flow process. Even though the nonlinear flow behaviour in single rock fractures has been studied for decades, existing models are still limited in adequately evaluating nonlinear flow behaviour during shearing. In this study, a series of coupled shear-flow tests are conducted on single rock fractures with different surface characteristics under constant normal loads. Regression analyses of the experimental data demonstrate that the Forchheimer equation provides a robust description of nonlinear flow through rough fractures, and its nonlinear coefficients can be determined by quantifying the fracture geometries. The surface and interior geometric characteristics of the fracture are quantitatively represented. The evolutions of these geometric parameters, specifically the peak asperity height and hydraulic aperture, induced by shearing and their effects on nonlinear flow behaviours in rock fractures are also considered and incorporated. An empirical equation is then proposed for the parametric expression of the Forchheimer nonlinear coefficient, which is further used for the prediction of the flow rate during the shear-flow process and the representation of the critical Reynolds number with the fracture geometric characteristics. The proposed equations are validated against experimental results and proven to be effective in predicting and characterising the nonlinear flow behaviour in rock fractures during shearing. The experimental results and the proposed models are expected to advance the understanding and numerical modelling of the nonlinear flow behaviours in fractured rock masses for more practical applications.","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"51 1","pages":""},"PeriodicalIF":7.2,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A micro-macro fracture model for evaluating the brittle-ductile transition and rockburst of rock in true triaxial compression","authors":"Xiaozhao Li, Lianjie Li, Yujie Yan, Chengzhi Qi","doi":"10.1016/j.ijrmms.2024.105993","DOIUrl":"https://doi.org/10.1016/j.ijrmms.2024.105993","url":null,"abstract":"In deep underground engineering, true triaxial compressive stress and internal microcrack characteristics significantly influence the brittle-ductile transition and anisotropic mechanical behavior of rock, thereby affecting the engineering life cycle. However, current research on the micro-macro mechanical model under true triaxial compressive stress, particularly regarding the rock's brittle-ductile transition and anisotropic damage, is extremely limited. This paper aims to propose a macro-micromechanical model to describe the aforementioned physical and mechanical properties of rocks. The model introduces a lateral stress function into the micro-macro damage formula and derives the axial stress-strain relationship during crack propagation by incorporating the stress-crack length relationship under true triaxial stress. By considering the stress effects on the effective elastic modulus and nominal Poisson's ratio, the lateral stress-strain relationship is derived, resulting in a complete stress-strain curve. Finally, based on the relationships between triaxial principal strains, elastic deformation and triaxial principal stresses, the relationships between rock volumetric strain, crack volumetric strain, and triaxial principal stress are separately established. The influence of lateral principal stress on characteristic stresses is analyzed. The resulting model is combined with the brittleness evaluation index and the residual elastic energy index, respectively, to analyze the effects of micro parameters and principal stresses on brittleness and rockburst proneness. A comparative analysis of the similarities and differences between brittleness and rockburst proneness is conducted, revealing a positive correlation between the ratio of residual elastic energy and the post-peak to pre-peak brittleness index, expressed as <mml:math altimg=\"si1.svg\"><mml:mrow><mml:msub><mml:mi>C</mml:mi><mml:mtext>EF</mml:mtext></mml:msub><mml:mo linebreak=\"goodbreak\" linebreakstyle=\"after\">∝</mml:mo><mml:msub><mml:mi>B</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">i</mml:mi><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo linebreak=\"goodbreak\" linebreakstyle=\"after\">/</mml:mo><mml:msub><mml:mi>B</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">i</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>. The proposed model theoretically addresses the issues of brittle-ductile transition and anisotropic damage under true triaxial conditions. It can also be applied to explain and predict rockburst proneness.","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"1 1","pages":""},"PeriodicalIF":7.2,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Onset of pore collapse and dilatancy in porous sandstone under true triaxial compression: Experimental observation and micromechanical modeling","authors":"Fanbao Meng, Lu Shi, Stephen Hall, Patrick Baud, Teng-fong Wong","doi":"10.1016/j.ijrmms.2024.105983","DOIUrl":"https://doi.org/10.1016/j.ijrmms.2024.105983","url":null,"abstract":"We present new true triaxial compression data obtained in the ductile regime on Bleurswiller sandstone. The deformed samples show a range of failure modes qualitatively similar to what was reported by earlier experimental studies performed in conventional conditions (axisymmetric compression). In particular, visual inspection and X-ray Computed Tomography imaging reveal compaction localization in all our deformed samples. The pore collapse model of Zhu et al.( 2010) <ce:sup loc=\"post\">1</ce:sup> is extended to include the role of the intermediate principal stress and our new data for the onset of shear-enhanced compaction are in basic agreement with this extended model that includes three stress invariants. Published true triaxial data obtained in the brittle regime highlights the impact of the intermediate principal stress on the onset of dilatancy. The predictions of the conventional sliding wing crack model extended to true triaxial conditions are in poor agreement with these data. Another energetic approach pioneered by Wiebols &amp; Cook shows a better agreement with the experimental results. Our new data and analysis will help the interpretation of inelastic deformation under polyaxial compression in various geotechnical and tectonic settings.","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"143 1","pages":""},"PeriodicalIF":7.2,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comprehensive in-situ stress estimation in a fractured geothermal reservoir in Pohang, South Korea using drilling data, hydraulic stimulations, and induced seismicity","authors":"Sehyeok Park, Kwang-Il Kim, Hwajung Yoo, Juhyi Yim, Ki-Bok Min","doi":"10.1016/j.ijrmms.2024.105978","DOIUrl":"https://doi.org/10.1016/j.ijrmms.2024.105978","url":null,"abstract":"A comprehensive in situ stress estimation is carried out in the fractured reservoir at the enhanced geothermal system development site in Pohang, South Korea. Various types of stress indicators were collected from the hydraulic stimulation data, drilling records, lost circulation records, well logs, seismic events, and the stress constraints from previously proposed stress models. The comprehensive comparison of the collected stress constraints was performed, and resulted in the possible stress magnitude range and corresponding limits on the range of possible friction coefficients. The resulting stress ratio is <ce:italic>S</ce:italic><ce:inf loc=\"post\"><ce:italic>V</ce:italic></ce:inf>: <ce:italic>S</ce:italic><ce:inf loc=\"post\"><ce:italic>hmin</ce:italic></ce:inf>: <ce:italic>S</ce:italic><ce:inf loc=\"post\"><ce:italic>Hmax</ce:italic></ce:inf> = 1 : 0.92–0.94 : 1.42–1.66 with the azimuth of <ce:italic>S</ce:italic><ce:inf loc=\"post\"><ce:italic>Hmax</ce:italic></ce:inf> in N101°E –N110°E range, based on the compilation of both direct and indirect stress information. The results also suggest a friction coefficient range of 0.35–0.38 that can best explain the involved stress constraints. The stress model suggested in this study can explain the characteristics of the M<ce:inf loc=\"post\">w</ce:inf> 5.5 Pohang earthquake in November 2017 in terms of reproducing the slip rake of mainshock and the slip tendency of the corresponding fault. Therefore, the result can be used for clarifying the causal mechanism of the Pohang earthquake, providing an insight for fault stability analysis or possible geo-energy application in the southeastern part of the Korean Peninsula. Comprehensive in-situ stress estimation method suggested in this study integrating extensive direct and indirect stress indicators can improve the credibility of the in-situ stress model at a fractured reservoir.","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"10 1","pages":""},"PeriodicalIF":7.2,"publicationDate":"2024-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142793448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strength changes associated with water transport in unsaturated tuff during drying","authors":"Yota Togashi, Haruhiko Kotabe, Masahiko Osada, Shingo Asamoto, Ken Hatakeyama","doi":"10.1016/j.ijrmms.2024.105984","DOIUrl":"https://doi.org/10.1016/j.ijrmms.2024.105984","url":null,"abstract":"The impact of water content on the strength of sedimentary rocks is a critical area of research, particularly in the contexts of disaster prevention and the construction of underground structures. Despite numerous factors being identified as contributors to the strength variations in sedimentary rocks caused by water content, a comprehensive understanding remains elusive. Moreover, only a limited number of cases have been discussed on strength changes in these rocks during water transport processes. In this study, one-dimensional water transport experiments were conducted during the drying process on Neogene tuff samples from Japan. The experiments focused on the unsaturated permeation of the porous media and analyzed the variations in advection and diffusion terms relative to saturation changes at multiple points. During the drying process, water transfer occurred primarily through diffusion, although advection was significant in the early stages to equilibrate the hydraulic head at the center of the specimen. Furthermore, the same tuff samples, with adjusted water content during the drying process, were tested using Brazilian and uniaxial compression methods to examine the variations in strength properties owing to the variations in water content. By comparing these results with the water transport data, we observed that significant alterations in strength occurred after the convergence of the advection term. It was shown for the first time that the decrease in strength of tuff occurs only during the water diffusion phase. These results are expected to be applied to more accurate evaluation of rock mass stability and advanced numerical analysis.","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"28 1","pages":""},"PeriodicalIF":7.2,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142793450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anisotropic acoustoelastic effective-medium model for stress-dependent elastic moduli of fractured rocks","authors":"Bo-Ye Fu, Li-Yun Fu","doi":"10.1016/j.ijrmms.2024.105979","DOIUrl":"https://doi.org/10.1016/j.ijrmms.2024.105979","url":null,"abstract":"Prestress significantly influences the mechanical properties of fractured rocks due to stress-induced anisotropy in the surrounding matrix and the stress-induced closure of cracks. Understanding the stress-dependent elastic moduli and anisotropic properties is crucial for various geoscience applications. The theory of acoustoelasticity only accounts for weak nonlinear elasticity with finite strains through the third-order elastic constants (3oECs) that are strictly valid for an isotropic homogeneous medium. Incorporating the David-Zimmerman (DZ) and Mori-Tanaka (MT) models into the theory of acoustoelasticity leads to an acoustoelastic DZ-MT model of fractured rocks. In this study, we extend the isotropic acoustoelastic DZ-MT model to address anisotropic conditions by examining two scenarios: one involving isotropic prestress applied to rocks with aligned cracks, and the other involving uniaxial prestress applied to rocks with isotropic cracks. The resulting anisotropic acoustoelastic DZ-MT model of fractured rocks is validated by experiment data measured from an artificial sample with aligned cracks and three isotropic sandstones (Massilon, Portland, and Berea). For the artificial sample, applying isotropic pressure will reduce the crack-induced anisotropy due to crack closure, leading in turn to increase the acoustoelastic effect on the background matrix as well as the effective elastic moduli of rocks. Aligned cracks primarily reduce the P-wave modulus for waves propagating perpendicular to the crack surfaces, making the P-wave modulus undergo significant changes because of its sensitivity to crack closure. For the natural sandstones with isotropic cracks subjected to uniaxial prestress, some existing cracks are closed, strongly depending on the relativity between crack orientation and loading direction. The P-wave modulus normal to the loading direction exhibits a slight increase, indicating the integrated effect of both acoustoelasticity and crack deformation. The complex microstructural changes in the case of uniaxial loading influence the application of acoustoelasticity and crack-closure model, potentially reducing the accuracy of the proposed DZ-MT model.","PeriodicalId":54941,"journal":{"name":"International Journal of Rock Mechanics and Mining Sciences","volume":"200 1","pages":""},"PeriodicalIF":7.2,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142793153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}