Rock and geotechnical engineering investigations involve drilling holes in ground with or without retrieving soil and rock samples to construct the subsurface ground profile.On the basis of an actual soil nailing dril...Rock and geotechnical engineering investigations involve drilling holes in ground with or without retrieving soil and rock samples to construct the subsurface ground profile.On the basis of an actual soil nailing drilling for a slope stability project in Hong Kong,this paper further develops the drilling process monitoring(DPM)method for digitally profiling the subsurface geomaterials of weathered granitic rocks using a compressed airflow driven percussive-rotary drilling machine with down-the-hole(DTH)hammer.Seven transducers are installed on the drilling machine and record the chuck displacement,DTH rotational speed,and five pressures from five compressed airflows in real-time series.The mechanism and operations of the drilling machine are elaborated in detail,which is essential for understanding and evaluating the drilling data.A MATLAB program is developed to automatically filter the recorded drilling data in time series and classify them into different drilling processes in sub-time series.These processes include penetration,push-in with or without rod,pull-back with or without rod,rod-tightening and rod-untightening.The drilling data are further reconstructed to plot the curve of drill-bit depth versus the net drilling time along each of the six drillholes.Each curve is found to contain multiple linear segments with a constant penetration rate,which implies a zone of homogenous geomaterial with different weathering grades.The effect from fluctuation of the applied pressures is evaluated quantitatively.Detailed analyses are presented for accurately assess and verify the underground profiling and strength in weathered granitic rock,which provided the basis of using DPM method to confidently assess drilling measurements to interpret the subsurface profile in real time.展开更多
Rockburst is becoming a huge challenge for the utilization of deep underground space.Extensive efforts have been devoted to investigating the rockburst behavior and mechanism experimentally,theoretically,and numerical...Rockburst is becoming a huge challenge for the utilization of deep underground space.Extensive efforts have been devoted to investigating the rockburst behavior and mechanism experimentally,theoretically,and numerically.The aim of this review is to discuss the novel development and the state-of-the-art in experimental techniques,theories,and numerical approaches proposed for rockburst.The definition and classification of rockburst are first summarized with an in-depth comparison among them.Then,the available laboratory experimental technologies for rockburst are reviewed in terms of indirect and direct approaches,with the highlight of monitoring technologies and data analysis methods.Some key rockburst influencing factors(i.e.size and shape,rock types,stress state,water content,and temperature)are analyzed and discussed based on collected data.After that,rockburst theories and mechanisms are discussed and evaluated,as well as the microscopic observation.The simulation approaches of rockburst are also summarized with the highlight of optional novel numerical methods.The accuracy,stability,and reliability of different experimental,theoretical and numerical approaches are also compared and assessed in each part.Finally,a summary and some aspects of prospective research are presented.展开更多
A circular shaft is often used to access a working well for deep underground space utilization.As the depth of underground space increases,the excavation depth of the shaft increases.In this study,the deformation char...A circular shaft is often used to access a working well for deep underground space utilization.As the depth of underground space increases,the excavation depth of the shaft increases.In this study,the deformation characteristics of a circular shaft with a depth of 56.3 m were presented and analysed.The main monitoring contents included:(1)wall deflection;(2)vertical wall movement;(3)horizontal soil movement;(4)vertical surface movement;and(5)basal heave.Horizontally,the maximum wall deflection was only 7.7 mm.Compared with the wall deflection data collected for another 29 circular excavations,the ratio of maximum wall deflection to excavation depth of this shaft was smaller due to a smaller ratio of diameter to excavation depth.The wall deflection underwent two stages of deformation:the first stage was mainly circumferential compression caused by the mutual extrusion of joints between walls,and the second stage was typical vertical deflection deformation.The horizontal soil movement outside the shaft was greater than the wall deflection and the deep soil caused great horizontal movement because of dewatering at confined water layers.Vertically,a basal heave of 203.8 mm occurred in the pit centre near the bottom.Meanwhile,the shaft was uplifted over time and showed 3 stages of vertical movement.The surface outside the shaft exhibited settlement and uplift deformation at different locations due to different effects.The basal heave caused by excavation was the dominant factor,driving the vertical movement of the shaft as well as the surrounding surface.The correlation between the wall deflection and the surface settlement outside the shaft was weak.展开更多
Contemporary demands necessitate the swift and accurate detection of cracks in critical infrastructures,including tunnels and pavements.This study proposed a transfer learning-based encoder-decoder method with visual ...Contemporary demands necessitate the swift and accurate detection of cracks in critical infrastructures,including tunnels and pavements.This study proposed a transfer learning-based encoder-decoder method with visual explanations for infrastructure crack segmentation.Firstly,a vast dataset containing 7089 images was developed,comprising diverse conditions—simple and complex crack patterns as well as clean and rough backgrounds.Secondly,leveraging transfer learning,an encoder-decoder model with visual explanations was formulated,utilizing varied pre-trained convolutional neural network(CNN)as the encoder.Visual explanations were achieved through gradient-weighted class activation mapping(Grad-CAM)to interpret the CNN segmentation model.Thirdly,accuracy,complexity(computation and model),and memory usage assessed CNN feasibility in practical engineering.Model performance was gauged via prediction and visual explanation.The investigation encompassed hyperparameters,data augmentation,deep learning from scratch vs.transfer learning,segmentation model architectures,segmentation model encoders,and encoder pre-training strategies.Results underscored transfer learning’s potency in enhancing CNN accuracy for crack segmentation,surpassing deep learning from scratch.Notably,encoder classification accuracy bore no significant correlation with CNN segmentation accuracy.Among all tested models,UNet-EfficientNet_B7 excelled in crack segmentation,harmonizing accuracy,complexity,memory usage,prediction,and visual explanation.展开更多
This paper aims to clarify the mechanism of the longitudinal response of a tunnel under normal faulting via a comprehensive analysis of available experimental data and numerical simulations.Four 1 g condition model te...This paper aims to clarify the mechanism of the longitudinal response of a tunnel under normal faulting via a comprehensive analysis of available experimental data and numerical simulations.Four 1 g condition model tests were reviewed and reanalysed to highlight the key characteristics of the tunnel response under normal faulting:S-shaped deformation and inverted S-shaped bending strain distribution in the longitudinal direction;the main affected zone of faulting is approximately six times the tunnel diameter to the fault plane.A threedimensional finite element model was also established and verified,followed by a sensitivity analysis of key parameters,including the fault dislocation,dip angle,tunnel rigidity and relative stiffness between the hanging wall and footwall.All results reveal that the longitudinal mechanical response under normal faulting is dominated by a combination of bending,tension,and shearing.Bending and shearing are induced by the large unbalanced rock pressure at the vault in the hanging wall and the inverted arch in the footwall;the value of unbalanced rock pressure is directly proportional to the dislocation but negatively correlated with the dip angle.Although the main part of the tunnel stays in tension,axial compressive strain exists around the fault plane when the dip angle is greater than 70 °,which may be related to the ovaling effect of the tunnel.Such an ovaling effect is caused by the compression at the cross-section of the tunnel and may lead to more complicated internal strain.展开更多
The tensile behavior of hybrid fiber reinforced concrete(HFRC)is important to the design of HFRC and HFRC structure.This study used an artificial neural network(ANN)model to describe the tensile behavior of HFRC.This ...The tensile behavior of hybrid fiber reinforced concrete(HFRC)is important to the design of HFRC and HFRC structure.This study used an artificial neural network(ANN)model to describe the tensile behavior of HFRC.This ANN model can describe well the tensile stress-strain curve of HFRC with the consideration of 23 features of HFRC.In the model,three methods to process output features(no-processed,mid-processed,and processed)are discussed and the mid-processed method is recommended to achieve a better reproduction of the experimental data.This means the strain should be normalized while the stress doesn’t need normalization.To prepare the database of the model,both many direct tensile test results and the relevant literature data are collected.Moreover,a traditional equation-based model is also established and compared with the ANN model.The results show that the ANN model has a better prediction than the equation-based model in terms of the tensile stress-strain curve,tensile strength,and strain corresponding to tensile strength of HFRC.Finally,the sensitivity analysis of the ANN model is also performed to analyze the contribution of each input feature to the tensile strength and strain corresponding to tensile strength.The mechanical properties of plain concrete make the main contribution to the tensile strength and strain corresponding to tensile strength,while steel fibers tend to make more contributions to these two items than PVA fibers.展开更多
The waterproofing capacity of segmental joints is an essential indicator for the long-term service performance of shield tunnels.The segmental joints with double gaskets have been adopted to improve the waterproof per...The waterproofing capacity of segmental joints is an essential indicator for the long-term service performance of shield tunnels.The segmental joints with double gaskets have been adopted to improve the waterproof performance for certain tunnels with high water pressure,especially water-conveyance tunnels.This paper presents a series of waterproofing tests on joints with different settings of double gaskets via an improved test apparatus.Four cases are investigated,including(i)double gaskets with equal high/low waterproof capacity,(ii)the outer gasket with higher waterproof capacity,and(iii)the outer gasket with lower waterproof capacity.Different joint openings are also considered.Moreover,the water pressures at two cavities are continuously monitored to highlight the waterproofing mechanism and failure pattern of double gaskets.The results demonstrate that the gasket with the higher waterproofing capacity dominates the overall waterproofing capacity of joint with double gaskets;only a little enhancement of the waterproofing capacity is found for the joint with the same double gaskets.The waterproofing capacity of joints with double gaskets decreases with the increase of the joint opening.The failure pattern depends on the arrangement of double gaskets,and four stages can be identified during the whole failure process.The advantages of double gaskets in case of joint rotation are also discussed.展开更多
In this study,a deep excavation in an under-consolidated deposit in Zhuhai,China,was reported and investigated via plane strain finite element analysis(FEA).First,the project was simulated via FEA(under-consolidated d...In this study,a deep excavation in an under-consolidated deposit in Zhuhai,China,was reported and investigated via plane strain finite element analysis(FEA).First,the project was simulated via FEA(under-consolidated deposit),and a reasonable agreement between the lateral displacement of the measured and simulated retaining wall was obtained.Another FEA was then conducted under the assumption that the deposit was in a normally consolidated state.The numerical results indicate that the under-consolidated case resulted in a 25% increase in maximum lateral displacement of the contiguous pile-formed retaining wall,a 32% increase in bending moment in the wall,and approximately twice the maximum surface settlement behind the wall,when compared with those of the normally consolidated case.The main reasons for this are as follows:(1)the under-consolidated deposit was weaker,and(2)the ongoing consolidation of the under-consolidated deposit induced green-field settlement(approximately 4 mm)during the project period,thereby enhancing the bending deformation of the wall.Therefore,when designing deep excavation in an under-consolidated deposit,not only its weaker strength but also the negative effect of green-field settlement during the project period should be considered.展开更多
基金supported by grants from the Research Grant Council of the Hong Kong Special Administrative Region,China(Project Nos.HKU 7137/03E and R7005/01E)。
文摘Rock and geotechnical engineering investigations involve drilling holes in ground with or without retrieving soil and rock samples to construct the subsurface ground profile.On the basis of an actual soil nailing drilling for a slope stability project in Hong Kong,this paper further develops the drilling process monitoring(DPM)method for digitally profiling the subsurface geomaterials of weathered granitic rocks using a compressed airflow driven percussive-rotary drilling machine with down-the-hole(DTH)hammer.Seven transducers are installed on the drilling machine and record the chuck displacement,DTH rotational speed,and five pressures from five compressed airflows in real-time series.The mechanism and operations of the drilling machine are elaborated in detail,which is essential for understanding and evaluating the drilling data.A MATLAB program is developed to automatically filter the recorded drilling data in time series and classify them into different drilling processes in sub-time series.These processes include penetration,push-in with or without rod,pull-back with or without rod,rod-tightening and rod-untightening.The drilling data are further reconstructed to plot the curve of drill-bit depth versus the net drilling time along each of the six drillholes.Each curve is found to contain multiple linear segments with a constant penetration rate,which implies a zone of homogenous geomaterial with different weathering grades.The effect from fluctuation of the applied pressures is evaluated quantitatively.Detailed analyses are presented for accurately assess and verify the underground profiling and strength in weathered granitic rock,which provided the basis of using DPM method to confidently assess drilling measurements to interpret the subsurface profile in real time.
基金supported by the National Natural Science Foundation of China(Grant No.41941018)Key Technology Research on Water Diversion Project for Central Area of Yunnan Province,China.All the supports are gratefully acknowledged.
文摘Rockburst is becoming a huge challenge for the utilization of deep underground space.Extensive efforts have been devoted to investigating the rockburst behavior and mechanism experimentally,theoretically,and numerically.The aim of this review is to discuss the novel development and the state-of-the-art in experimental techniques,theories,and numerical approaches proposed for rockburst.The definition and classification of rockburst are first summarized with an in-depth comparison among them.Then,the available laboratory experimental technologies for rockburst are reviewed in terms of indirect and direct approaches,with the highlight of monitoring technologies and data analysis methods.Some key rockburst influencing factors(i.e.size and shape,rock types,stress state,water content,and temperature)are analyzed and discussed based on collected data.After that,rockburst theories and mechanisms are discussed and evaluated,as well as the microscopic observation.The simulation approaches of rockburst are also summarized with the highlight of optional novel numerical methods.The accuracy,stability,and reliability of different experimental,theoretical and numerical approaches are also compared and assessed in each part.Finally,a summary and some aspects of prospective research are presented.
基金the National Natural Science Foundation of China(Grant No.52090083)Shanghai Chenguang Program(Grant No.20CG26)Consulting project on Shanghai deep tunnel project.
文摘A circular shaft is often used to access a working well for deep underground space utilization.As the depth of underground space increases,the excavation depth of the shaft increases.In this study,the deformation characteristics of a circular shaft with a depth of 56.3 m were presented and analysed.The main monitoring contents included:(1)wall deflection;(2)vertical wall movement;(3)horizontal soil movement;(4)vertical surface movement;and(5)basal heave.Horizontally,the maximum wall deflection was only 7.7 mm.Compared with the wall deflection data collected for another 29 circular excavations,the ratio of maximum wall deflection to excavation depth of this shaft was smaller due to a smaller ratio of diameter to excavation depth.The wall deflection underwent two stages of deformation:the first stage was mainly circumferential compression caused by the mutual extrusion of joints between walls,and the second stage was typical vertical deflection deformation.The horizontal soil movement outside the shaft was greater than the wall deflection and the deep soil caused great horizontal movement because of dewatering at confined water layers.Vertically,a basal heave of 203.8 mm occurred in the pit centre near the bottom.Meanwhile,the shaft was uplifted over time and showed 3 stages of vertical movement.The surface outside the shaft exhibited settlement and uplift deformation at different locations due to different effects.The basal heave caused by excavation was the dominant factor,driving the vertical movement of the shaft as well as the surrounding surface.The correlation between the wall deflection and the surface settlement outside the shaft was weak.
基金the National Natural Science Foundation of China(Grant Nos.52090083 and 52378405)Key Technology R&D Plan of Yunnan Provincial Department of Science and Technology(Grant No.202303AA080003)for their financial support.
文摘Contemporary demands necessitate the swift and accurate detection of cracks in critical infrastructures,including tunnels and pavements.This study proposed a transfer learning-based encoder-decoder method with visual explanations for infrastructure crack segmentation.Firstly,a vast dataset containing 7089 images was developed,comprising diverse conditions—simple and complex crack patterns as well as clean and rough backgrounds.Secondly,leveraging transfer learning,an encoder-decoder model with visual explanations was formulated,utilizing varied pre-trained convolutional neural network(CNN)as the encoder.Visual explanations were achieved through gradient-weighted class activation mapping(Grad-CAM)to interpret the CNN segmentation model.Thirdly,accuracy,complexity(computation and model),and memory usage assessed CNN feasibility in practical engineering.Model performance was gauged via prediction and visual explanation.The investigation encompassed hyperparameters,data augmentation,deep learning from scratch vs.transfer learning,segmentation model architectures,segmentation model encoders,and encoder pre-training strategies.Results underscored transfer learning’s potency in enhancing CNN accuracy for crack segmentation,surpassing deep learning from scratch.Notably,encoder classification accuracy bore no significant correlation with CNN segmentation accuracy.Among all tested models,UNet-EfficientNet_B7 excelled in crack segmentation,harmonizing accuracy,complexity,memory usage,prediction,and visual explanation.
基金finically supported by the National Natural Science Foundation of China(No.41941018),2019QZKK0708Key Technology Research on Water Diversion Project for Central Area of Yunnan Province.
文摘This paper aims to clarify the mechanism of the longitudinal response of a tunnel under normal faulting via a comprehensive analysis of available experimental data and numerical simulations.Four 1 g condition model tests were reviewed and reanalysed to highlight the key characteristics of the tunnel response under normal faulting:S-shaped deformation and inverted S-shaped bending strain distribution in the longitudinal direction;the main affected zone of faulting is approximately six times the tunnel diameter to the fault plane.A threedimensional finite element model was also established and verified,followed by a sensitivity analysis of key parameters,including the fault dislocation,dip angle,tunnel rigidity and relative stiffness between the hanging wall and footwall.All results reveal that the longitudinal mechanical response under normal faulting is dominated by a combination of bending,tension,and shearing.Bending and shearing are induced by the large unbalanced rock pressure at the vault in the hanging wall and the inverted arch in the footwall;the value of unbalanced rock pressure is directly proportional to the dislocation but negatively correlated with the dip angle.Although the main part of the tunnel stays in tension,axial compressive strain exists around the fault plane when the dip angle is greater than 70 °,which may be related to the ovaling effect of the tunnel.Such an ovaling effect is caused by the compression at the cross-section of the tunnel and may lead to more complicated internal strain.
基金The authors would like to acknowledge the National Natural Science Foundation of China(Grant Nos.51978515,41941018)Shanghai Sailing Program(19YF1451400)Shanghai Municipal Science and Technology Major Project(2017SHZDZX02)for their financial support.
文摘The tensile behavior of hybrid fiber reinforced concrete(HFRC)is important to the design of HFRC and HFRC structure.This study used an artificial neural network(ANN)model to describe the tensile behavior of HFRC.This ANN model can describe well the tensile stress-strain curve of HFRC with the consideration of 23 features of HFRC.In the model,three methods to process output features(no-processed,mid-processed,and processed)are discussed and the mid-processed method is recommended to achieve a better reproduction of the experimental data.This means the strain should be normalized while the stress doesn’t need normalization.To prepare the database of the model,both many direct tensile test results and the relevant literature data are collected.Moreover,a traditional equation-based model is also established and compared with the ANN model.The results show that the ANN model has a better prediction than the equation-based model in terms of the tensile stress-strain curve,tensile strength,and strain corresponding to tensile strength of HFRC.Finally,the sensitivity analysis of the ANN model is also performed to analyze the contribution of each input feature to the tensile strength and strain corresponding to tensile strength.The mechanical properties of plain concrete make the main contribution to the tensile strength and strain corresponding to tensile strength,while steel fibers tend to make more contributions to these two items than PVA fibers.
基金financially supported by National Natural Science Foundation of China(52090083)Shanghai Committee of Science and Technology(20DZ1202600)China Railway Southern Investment Group Co.Ltd(Project No.ZTNF-2020-1).
文摘The waterproofing capacity of segmental joints is an essential indicator for the long-term service performance of shield tunnels.The segmental joints with double gaskets have been adopted to improve the waterproof performance for certain tunnels with high water pressure,especially water-conveyance tunnels.This paper presents a series of waterproofing tests on joints with different settings of double gaskets via an improved test apparatus.Four cases are investigated,including(i)double gaskets with equal high/low waterproof capacity,(ii)the outer gasket with higher waterproof capacity,and(iii)the outer gasket with lower waterproof capacity.Different joint openings are also considered.Moreover,the water pressures at two cavities are continuously monitored to highlight the waterproofing mechanism and failure pattern of double gaskets.The results demonstrate that the gasket with the higher waterproofing capacity dominates the overall waterproofing capacity of joint with double gaskets;only a little enhancement of the waterproofing capacity is found for the joint with the same double gaskets.The waterproofing capacity of joints with double gaskets decreases with the increase of the joint opening.The failure pattern depends on the arrangement of double gaskets,and four stages can be identified during the whole failure process.The advantages of double gaskets in case of joint rotation are also discussed.
基金financially sponsored by National Foreign Experts and Talents Project of China(G20190009128)the Consulting Project on Hengqin Foundation Pits(CSCEC2B-SZ-HQKA-ZY-080)Shanghai Municipal Science and Technology Major Project(2017SHZDZX02),China.
文摘In this study,a deep excavation in an under-consolidated deposit in Zhuhai,China,was reported and investigated via plane strain finite element analysis(FEA).First,the project was simulated via FEA(under-consolidated deposit),and a reasonable agreement between the lateral displacement of the measured and simulated retaining wall was obtained.Another FEA was then conducted under the assumption that the deposit was in a normally consolidated state.The numerical results indicate that the under-consolidated case resulted in a 25% increase in maximum lateral displacement of the contiguous pile-formed retaining wall,a 32% increase in bending moment in the wall,and approximately twice the maximum surface settlement behind the wall,when compared with those of the normally consolidated case.The main reasons for this are as follows:(1)the under-consolidated deposit was weaker,and(2)the ongoing consolidation of the under-consolidated deposit induced green-field settlement(approximately 4 mm)during the project period,thereby enhancing the bending deformation of the wall.Therefore,when designing deep excavation in an under-consolidated deposit,not only its weaker strength but also the negative effect of green-field settlement during the project period should be considered.
