The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challe...The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challenges of a composite strata roadway in deep and soft rock masses,a numerical model of 3DEC tetrahedral blocks was established based on the method of rock quality designation(RQD).The results showed that original support cannot prevent asymmetric failure and large deformation due to the adverse geological environment and unsuitable support design.According to the failure characteristics,a coupling support of“NPR bolt/cable+mesh+shotcrete+steel pipe”was proposed to control the stability of the surrounding rock.The excellent mechanical properties of large deformation(approximately 400 mm)and high constant resistance force(bolt with 180 k N;cable with 350 k N)were evaluated by the tensile tests.The numerical results showed that the maximum deformation was minimized to 243 mm,and the bearing capacity of the surrounding rock of the roadway was enhanced.The field test results showed that the maximum deformation of the surrounding rock was 210 mm,and the forces of the NPR bolt and cable were stable at approximately 180 k N and 350 k N,respectively.This demonstrated the effectiveness of the coupling support with the NPR bolt and cable,which could be a guiding significance for the safety control of large deformation and failure in deep composite soft rock roadways.展开更多
Due to the large differences in physico-mechanical pro perties of composite strata,jamming,head sinking and other serious consequences occur frequently during tunnel boring machine(TBM)excavation.To analyse the stabil...Due to the large differences in physico-mechanical pro perties of composite strata,jamming,head sinking and other serious consequences occur frequently during tunnel boring machine(TBM)excavation.To analyse the stability of surrounding rocks in composite strata under the disturbance of TBM excavation,a geomechanical model test was carried out based on the Lanzhou water supply project.The evolution patterns and distribution characteristics of the strain,stress,and tunnel deformation and fracturing were analysed.The results showed that during TBM excavation in the horizontal composite formations(with upper soft and lower hard layers and with upper hard and lower soft layers),a significant difference in response to the surrounding rocks can be observed.As the strength ratio of the surrounding rocks decreases,the ratio of the maximum strain of the hard rock mass to that of the relatively soft rock mass gradually decreases.The radial stress of the relatively soft rock mass is smaller than that of the hard rock mass in both types of composite strata,indicating that the weak rock mass in the composite formation results in the difference in the mechanical behaviours of the surrounding rocks.The displacement field of the surrounding rocks obtained by the digital speckle correlation method(DSCM)and the macro-fracture morphology after tunnel excavation visually reflected the deformation difference of the composite rock mass.Finally,some suggestions and measures were provided for TBM excavation in composite strata,such as advance geological forecasting and effective monitoring of weak rock masses.展开更多
A study of REE compositions of Sinian to Triassic sedimentary strata from Guichi stratigraphic region located in northern margin of the Yangtze block indicates that average total REE concentration is 127μg/g which is...A study of REE compositions of Sinian to Triassic sedimentary strata from Guichi stratigraphic region located in northern margin of the Yangtze block indicates that average total REE concentration is 127μg/g which is lower than that of sedimentary rocks from the whole world(230 μg/g) and approximately resembles to that of sedimentary rocks from the platforms(129 μg/g). Among different lithologies, average total REE concentration of shales is the highest(230 μg/g), that of limestones is the lowest(18 μg/g) and that of sandstones and siltstones is in between(213 μg/g) .REE concentrations of strata of different geologic ages are controlled by lithology.REE concentrations of Ordovician and Triasaic strata consisting mostly of carbonate rocks are the lowest(40 and 44 μg/g, respectively), and those of Silulian and Devonian strata consisting mainly of terrestrial detrital rocks are the highest (231 and 248 μg/g, respectively). Sedimentary rocks studied show very similar REE patterns with LREE enrichment and negative Eu anomaly regardless of lithology and stratigraphic age. Samples are plotted in a confined area in Σ(La～Nd)-Σ(Sm～Ho)-Σ(Er～Lu) ternary plot, suggesting homogeneity of REE composition and a stable environment for the studied region. Similarity between REE compositions of sedimentary rocks from the studied region and that from typical platforms of the world suggests the platform character of the studied region during Sinica to Triassic. Results of this study suggests that the provenance of the studied sedimentary rocks is not the Jiangnanian old land mass, but the old continent(s) from the north.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51874311,52174096)。
文摘The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challenges of a composite strata roadway in deep and soft rock masses,a numerical model of 3DEC tetrahedral blocks was established based on the method of rock quality designation(RQD).The results showed that original support cannot prevent asymmetric failure and large deformation due to the adverse geological environment and unsuitable support design.According to the failure characteristics,a coupling support of“NPR bolt/cable+mesh+shotcrete+steel pipe”was proposed to control the stability of the surrounding rock.The excellent mechanical properties of large deformation(approximately 400 mm)and high constant resistance force(bolt with 180 k N;cable with 350 k N)were evaluated by the tensile tests.The numerical results showed that the maximum deformation was minimized to 243 mm,and the bearing capacity of the surrounding rock of the roadway was enhanced.The field test results showed that the maximum deformation of the surrounding rock was 210 mm,and the forces of the NPR bolt and cable were stable at approximately 180 k N and 350 k N,respectively.This demonstrated the effectiveness of the coupling support with the NPR bolt and cable,which could be a guiding significance for the safety control of large deformation and failure in deep composite soft rock roadways.
基金supported by the National Natural Science Foundation of China(Grant No.41941018)the National Program on Key Basic Research of China(973 Program)(Grant No.2014CB046902)The partial support from the Hubei Province Natural Science Foundation Innovation Group(Grant No.2018CFA013)。
文摘Due to the large differences in physico-mechanical pro perties of composite strata,jamming,head sinking and other serious consequences occur frequently during tunnel boring machine(TBM)excavation.To analyse the stability of surrounding rocks in composite strata under the disturbance of TBM excavation,a geomechanical model test was carried out based on the Lanzhou water supply project.The evolution patterns and distribution characteristics of the strain,stress,and tunnel deformation and fracturing were analysed.The results showed that during TBM excavation in the horizontal composite formations(with upper soft and lower hard layers and with upper hard and lower soft layers),a significant difference in response to the surrounding rocks can be observed.As the strength ratio of the surrounding rocks decreases,the ratio of the maximum strain of the hard rock mass to that of the relatively soft rock mass gradually decreases.The radial stress of the relatively soft rock mass is smaller than that of the hard rock mass in both types of composite strata,indicating that the weak rock mass in the composite formation results in the difference in the mechanical behaviours of the surrounding rocks.The displacement field of the surrounding rocks obtained by the digital speckle correlation method(DSCM)and the macro-fracture morphology after tunnel excavation visually reflected the deformation difference of the composite rock mass.Finally,some suggestions and measures were provided for TBM excavation in composite strata,such as advance geological forecasting and effective monitoring of weak rock masses.
文摘A study of REE compositions of Sinian to Triassic sedimentary strata from Guichi stratigraphic region located in northern margin of the Yangtze block indicates that average total REE concentration is 127μg/g which is lower than that of sedimentary rocks from the whole world(230 μg/g) and approximately resembles to that of sedimentary rocks from the platforms(129 μg/g). Among different lithologies, average total REE concentration of shales is the highest(230 μg/g), that of limestones is the lowest(18 μg/g) and that of sandstones and siltstones is in between(213 μg/g) .REE concentrations of strata of different geologic ages are controlled by lithology.REE concentrations of Ordovician and Triasaic strata consisting mostly of carbonate rocks are the lowest(40 and 44 μg/g, respectively), and those of Silulian and Devonian strata consisting mainly of terrestrial detrital rocks are the highest (231 and 248 μg/g, respectively). Sedimentary rocks studied show very similar REE patterns with LREE enrichment and negative Eu anomaly regardless of lithology and stratigraphic age. Samples are plotted in a confined area in Σ(La～Nd)-Σ(Sm～Ho)-Σ(Er～Lu) ternary plot, suggesting homogeneity of REE composition and a stable environment for the studied region. Similarity between REE compositions of sedimentary rocks from the studied region and that from typical platforms of the world suggests the platform character of the studied region during Sinica to Triassic. Results of this study suggests that the provenance of the studied sedimentary rocks is not the Jiangnanian old land mass, but the old continent(s) from the north.
