Tunnelling and Underground Space Technology最新文献

{"title":"Research on the prestress Regulation of double-layer lining of shield water tunnel under high internal water pressure","authors":"","doi":"10.1016/j.tust.2024.106133","DOIUrl":"10.1016/j.tust.2024.106133","url":null,"abstract":"<div><div>Prestressed double-layer lining (segmental lining and prestressed lining) of shield tunnels has good seepage resistance and strong stability, and is a new type of support structure with great potential in high internal water pressure water transmission projects. For prestressed water conveyance tunnel projects, the reasonable value of lining tensioning prestress is the key to the economy and safety of the project. Accordingly, relying on the Pearl River Delta Water Resources Allocation Project, designed similar model tests for prestressed double-layer lining of water conveyance shield tunnels under the completed cable tension condition (CCTC) and design water pressure condition (DWPC) and established the corresponding ABAQUS three-dimensional finite element model to investigate the variations in the mechanical characteristics of the double-layer lining structure under different prestress conditions. The study determined the reasonable prestress range for the inner lining under a design internal water pressure of 1.5 MPa. The results indicated that under the CCTC, the prestressed lining is pressurized in the whole ring, the overall displacement level of the segmental lining is lower than that of the prestressed lining, the double-layer lining contact surface has a tendency to be detached, and with the increase of the structural prestress, the pressurized damage of the prestressed lining concrete develops gradually. Under the DWPC, the double-layer lining contact surface is completely closed under the action of internal water pressure, and the cracking risk of prestressed lining concrete increases with the decrease of prestress. Through numerical simulation, the reasonable range of prestressing force for shield tunnel lining is 68 %<em>σ</em>_con ∼ 137 %<em>σ</em>_con, and the results can provide a reference for the design and construction of prestressed double-layer lining structures of similar shield water tunnels.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533597","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":"Method for determining yield state and new solutions for stress and displacement fields of cold region tunnels under freeze-thaw cycles","authors":"","doi":"10.1016/j.tust.2024.106139","DOIUrl":"10.1016/j.tust.2024.106139","url":null,"abstract":"<div><div>The water-bearing surrounding rock in cold region tunnels is significantly affected by freeze-thaw (F-T) cycles generated by seasonal temperature changes, which can severely lead to tunnel lining failure due to increased loads. This study considers the non-uniform frost heave properties and the deterioration effects of F-T cycles on the surrounding rock. Six mechanical models for cold region tunnels are established based on the different yield states of frozen and unfrozen surrounding rock. Utilizing the unified strength theory, the solutions of stress and displacement fields for each model are derived, respectively, and a method for identifying the actual yield state of the tunnel is provided. The derived solutions are compared and verified, and the influence of various parameters on the solutions and yield states of cold region tunnels is explored. It is indicated herein that the proposed solutions have been validated by the results in the literature, demonstrating broad theoretical significance and practical engineering guidance value. When the F-T cycle counts increase from 0 to 75, the support pressure rises by 48.54%, and the plastic zone expands by 0.76 m. The deterioration effects of long-term F-T cycles on surrounding rocks should be quantified. As the intermediate principal stress effect increases, the support pressure decreases by 15.35%, and the development of the plastic zone is restricted. The unified strength theory should be used as the yield criterion. The greater the degree of non-uniform frost heave, the greater the load borne by the support structure. Insulation measures should be adopted to prevent excessive temperature gradients in the surrounding rock. In addition, failing to utilize the mechanical model corresponding to the actual yield state will result in significant calculation errors. The yield state determination method proposed in this study should be adopted. The results can offer theoretical references for designing cold region tunnels and safeguarding tunnel structures during service periods under F-T cycles.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533004","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":"Seepage field and drainage system in the connection part of underwater tunnel based on conformal mapping method","authors":"","doi":"10.1016/j.tust.2024.106146","DOIUrl":"10.1016/j.tust.2024.106146","url":null,"abstract":"<div><div>Composite construction methods may be adopted for some underwater tunnels due to complex geological conditions. However, the seepage field and the drainage system at connection part characterized by irregular cross-section are rarely reported. This study used the Zhujiangkou underwater tunnel as an engineering case, where the non-circular cross-section of the connection part was converted to the circular shape through the combination of the conformal mapping method and genetic algorithm. Additionally, the longitudinal seepage law in geotextile was developed, allowing for the theoretical deduction of the seepage field of tunnel with irregular cross-section while considering the role of the drainage system. The analytical results were validated through degradation tests and compared with numerical simulations and practical monitoring data. Moreover, the impacts of waterproofing and drainage system parameters on water inflow and water pressure were discussed. The results indicate that the water inflow increases as the distance between circumferential drainage pipes decreases and both the thickness and permeability coefficient of the geotextile increase, while the water pressure on lining decreases conversely, highlighting the significant influence of the drainage system. These findings can guide the design of the waterproofing and drainage system through parameter optimization for the consideration of safety and economy.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554661","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":"Investigation into the properties of two-component backfilling grouts prepared by substituting bentonite with slurry from slurry shield tunnelling treated by a hydrocyclone","authors":"","doi":"10.1016/j.tust.2024.106142","DOIUrl":"10.1016/j.tust.2024.106142","url":null,"abstract":"","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554662","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":"Dynamic planning of crowd evacuation path for metro station based on Dynamic Avoid Smoke A-Star algorithm","authors":"","doi":"10.1016/j.tust.2024.106145","DOIUrl":"10.1016/j.tust.2024.106145","url":null,"abstract":"<div><div>Considerable casualties can easily be caused once a fire occurs in a metro station, and a safe and effective evacuation path in time should be provided, taking on critical significance in the rapid evacuation of the crowd. In existing research, crowd evacuation paths have been generally planned without considering the fire environment and the real-time effect of fire products on the evacuation paths, such that the planned paths do not fit the realistic environment of crowd evacuation. An algorithm is proposed in this study to dynamically plan evacuation paths in fire scenarios in metro stations. First, the equivalent length of the path under the effect of fire on evacuation speed is determined in accordance with the effects of ambient temperature, visibility, and CO concentration, and then the fire risk model is built. Second, the fire risk model is incorporated into the A-Star algorithm, and the evaluation function of the A-Star algorithm is optimized, such that the determined path is capable of avoiding areas with higher fire risk. Subsequently, a dynamic update mechanism considering time factor is introduced to update the search environment information data of the algorithm in real time for dynamic path planning, with the aim of coping with the dynamically changing fire environment. Lastly, the A-Star algorithm is optimized, and the Dynamic Avoid-Smoke A-Star (DASA-Star) algorithm is built. As indicated by the simulation results, the DASA-Star algorithm is capable of making a trade-off between the fire risk and geometric length of the path in an underground station fire scenario and achieving dynamic planning of evacuation paths based on FDS fire simulation results. Accordingly, the algorithm conforms to the real-time requirements of path planning under fire conditions, and it is capable of more effectively planning the optimal evacuation path under the effect of fire.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554663","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":"Mechanism of structural defects in cut-and-cover tunnels within high-fill regions and gradient pile foundation reinforcement technology","authors":"","doi":"10.1016/j.tust.2024.106123","DOIUrl":"10.1016/j.tust.2024.106123","url":null,"abstract":"<div><div>Tunnel traverses high-fill soil-rock mixtures regions will often be susceptible to structural defects, which necessitate strata reinforcement. To mitigate the extent of these defects, this study employs a combination of model tests and numerical simulations to investigate the stability of tunnel structures. The mechanisms of structural defects were clarified, the influence of different soil-rock mixture strata shapes on structural defects was investigated, and a gradient pile foundation reinforcement technique was proposed based on this engineering case. The findings reveal that the primary manifestations of structural defects are various types of cracks, which developed in regard to the depth of the high-fill soil-rock mixture at the tunnel base, the self-settlement of the mixture, and the layer-by-layer backfilling at the tunnel vault. The differences between the model test and numerical simulation results are minimal, indicating that the shape of the soil-rock mixture stratum can significantly influence structural defects. The gradient pile reinforcement technology reduced tunnel settlement by up to 73.0%, while the foundation’s bearing capacity met the required standards, effectively controlling both tunnel settlement and structural defects. In terms of reinforcement for non-horizontal strata, gradient pile reinforcement technology demonstrates good adaptability, providing a feasible solution for similar engineering projects.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446032","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 rapid method for measuring the rock brittleness index: Rapid characterization of rock brittleness based on LIBS technology","authors":"","doi":"10.1016/j.tust.2024.106143","DOIUrl":"10.1016/j.tust.2024.106143","url":null,"abstract":"<div><div>The brittle index is a crucial indicator in the assessment of rockbursts. The mineral brittle index (MBI) is widely utilized due to its simplicity and accessibility. However, the lengthy and inefficient mineral composition testing cycle presents a significant challenge. A novel approach using laser-induced breakdown spectroscopy (LIBS) to rapidly convert spectral elements into minerals and measure the rock brittleness index was introduced in this paper. The laser spectra of metamorphic sandstone and granite were measured by LIBS, and some rock elements were tested by X-ray fluorescence (XRF) to construct a spectral-elemental model. Furthermore, the mineral composition of the rocks was determined by X-ray diffraction (XRD). Eight major elements, Si, Al, K, Ca, Na, Fe, Mg, and Ti, were selected as independent variables. Element-mineral correlation analysis was performed using centered log-ratio transformation (CLR) processing. A random forest regression (RF-R) element-mineral transformation model was established for rapid conversion of spectral-element-mineral brittle index. Finally, mechanical testing of rock embrittlement in the DJ Tunnel was conducted to verify the efficacy of MBI in characterizing rock embrittlement in the DJ Tunnel. The results demonstrate that predicted values of mineral compositions are in good agreement with experimental values and that predicted values of brittleness indices are also in good agreement with experimental values. The rapid and effective application of LIBS in determining rock mineral composition and rock brittleness index has been realised, which is of great significance for further realising the rapid assessment of rock brittleness and rockburst prediction at engineering sites.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142442363","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":"Time-arrival pickup method of tunnel water inrush microseismic signals based on kurtosis value and AIC method","authors":"","doi":"10.1016/j.tust.2024.106135","DOIUrl":"10.1016/j.tust.2024.106135","url":null,"abstract":"<div><div>One of the main factors affecting microseismic positioning is the travel time of microseismic waves, that is, the accuracy of picking up microseismic waves when they arrive. Although the manual pick-up has high accuracy in the arrival pick-up of microseismic signals, it has low working efficiency and is seriously affected by human activities, so it is difficult to cope with the huge amount of microseismic information. In order to solve the above problems, this paper proposes a K-AIC microseismic signal arrival pick-up method based on the fusion of the kurtosis value of higher-order statistics (PAI-K) and the Akachi information criterion (AIC). This method not only effectively reduces the dependence of kurtosis method on the size of sliding time window, but also solves the problems of weak anti-noise ability of AIC method and poor pick-up accuracy of low signal-to-noise ratio signal. By comparing the kurtosis, skewness, AIC method and artificial average picking results, the accuracy of the picking results proposed in this paper is verified by using the microseismic signals of water inrush obtained by indoor model test and the microseismic signals measured on site.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142442362","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":"Intelligent prediction and visual optimization of surface settlement induced by earth pressure balance shield tunneling","authors":"","doi":"10.1016/j.tust.2024.106138","DOIUrl":"10.1016/j.tust.2024.106138","url":null,"abstract":"<div><div>Surface settlement (Ss) caused by earth pressure balance (EPB) shield tunneling is a threat to the safety of surface buildings and underground tunnel structures. To that end, a novel intelligent model named the beluga whale optimization-based kernel-extreme learning machine (BWO-KELM) model is proposed to predict the Ss. 148 monitored data with three categories of eight features collected from three tunnel projects are adopted to train the proposed models. The results of model evaluation indicate that the BWO-KELM model established by using eight features achieve the most satisfactory performance indices (determination coefficient (R²), root mean square error (RMSE), variance accounted for (VAF), and the prediction accuracy (U1)) in both training and testing phases, i.e., R² (0.9544 and 0.9481), RMSE (3.4948 and 4.3239), VAF (95.4380 % and 94.8875 %), and U1 (0.0833 and 0.0938). Then, the model interpretability is enhanced by using the feature importance (FI) and Shapley additive explanations (SHAP) method. The results show that the mean moisture content (MC) of the soil layers is the most important feature for the Ss prediction. Finally, a visualization program is established to improve the prediction efficiency of Ss, reliability of risk assessment, and rationality of tunnel designs. This paper provides a novel intelligent model paradigm and a visualization program with a strong application for solving the problems induced by EPB shield tunneling.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438023","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":"Energy evolution and failure mechanism of tunnel dynamic unloading in deep rock mass abounding in closable minor joints","authors":"","doi":"10.1016/j.tust.2024.106132","DOIUrl":"10.1016/j.tust.2024.106132","url":null,"abstract":"<div><div>Discontinuities, ranging from micro to macro, are prevalent in natural rocks, especially deep brittle rock masses subjected to high in-situ stress. Previous studies on the unloading of deep tunnels have focused on large-scale discontinuities and have paid little attention to ubiquitous minor joints. These compactable joints affect static performance (strength and deformation characteristics) and dynamic response (stress wave concentration and dispersion). Through modelling, calibration, and validation, the jointed rock mass model in this study can demonstrate nonlinear deformation behaviour under static compression and increased wave velocity with increasing confining pressure under dynamic loading. Then, the Fourier transform method is utilised to solve the elastic theory solution of exponential unloading, and the excavation relaxation method is employed to simulate the tunnel unloading process in Particle Flow Code. The accuracy of the simulation process and measurement are analysed by comparing the theoretical solutions and the simulation results. The dynamic stress, failure pattern, and energy evolution of tunnel unloading in jointed rock masses are analysed from three influencing factors: unloading rate, lateral pressure coefficient, and dip angle distribution. Results indicate that joints are dynamic disturbance amplifiers near the tunnel and reducers at greater distances; additionally, the increase in the unloading rate will intensify these effects. Initial joint characteristics and in-situ stress determine the distribution of open joints and, thus, the wavefront shape. When most joints are closed under in-situ stress with low lateral coefficients, more severe tensile failure occurs in the direction perpendicular to the joint dip angle; conversely, when these joints are open, more severe shear damage will occur along the direction of the joint. The kinetic energy core shifts marginally from the direction of maximal principal stress towards the vertical of the joint dip angle, indicating that existing projects in this direction will be disturbed later but severely. Therefore, compactable minor joints should be considered to comprehend the dynamic response of tunnel unloading and to evaluate surrounding rock disturbance and failure.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433659","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}