Tunnelling and Underground Space Technology最新文献

Constrained by various factors, including terrain, tunnels frequently exhibit slopes. While existing research on fires in inclined tunnels predominantly focuses on the characteristics of smoke flow in large slope tunnels, there is a notable lack of attention given to the study of micro-slope tunnels and important factors such as induced air inflow. Therefore, in this paper, the numerical simulation method is used to study the maximum ceiling temperature rise and downstream temperature distribution in inclined tunnel fire under the conditions of micro-slope and large slope. The results show that the main factors affecting the ceiling temperature rise are not only the tunnel slope, but also the HRR and the downstream length. These effects can be expressed by the stack effect intensity. When the inclined tunnel fire occurs, the maximum ceiling temperature and the downstream temperature distribution characteristics show two states. When the stack effect in the tunnel is diminished, there is no significant alteration in the maximum ceiling temperature and temperature distribution within the tunnel when compared to a horizontal tunnel. In a tunnel with a strong stack effect, the maximum temperature decreases as the stack effect increases, and the temperature distribution differs greatly from a horizontal tunnel. The theoretical analysis of this paper identifies the demarcation point of the two state changes as the dimensionless induced air inflow velocity of 0.1. On this basis, a piecewise prediction model for the maximum ceiling temperature of the inclined tunnel fire is established. Because the temperature distribution between the fire source and the maximum temperature position is not regular. Thus, using the maximum ceiling temperature as a reference point, an accurate segmented prediction model of temperature distribution is proposed for downstream Region 1. This study offers guidance for designing tunnel structures with high-temperature resistance and assessing safety conditions within the tunnel.

Geological challenges in tunnel construction have consistently played a pivotal role in influencing project progress and safety. Accurate tunnel formation data holds the potential to assist in effectively managing various issues encountered during shield tunneling operations. This paper introduces a machine learning methodology for real-time tunnel geological prediction, based on the shield machine tunnelling parameters, as applied to the construction project of Chengdu Metro Line No.18 III phase. This method serves to enable timely formation identification and swift classification forecasting while tunneling progresses. Firstly, a new data pre-processing framework for real-time geological prediction is proposed. The 18 shield driving parameters in the daily report of the shield machine were selected as input features, which reduced the data by 2 orders of magnitude while retaining the geological characteristics of the data. Subsequently, leveraging the Dung Beetle Optimizer (DBO) and K-means algorithm, formation identification is carried out and validated against borehole data, enabling the acquisition of shield excavation data integrated with geological labels. Finally, 9 machine learning classification methods are used to classify and predict the data with geological label information, which proves that the tree-based classifier has strong interpretability for stratigraphic information and summarizes three boundary recognition modes of shield traversing different strata. The results show that: (1) the DBO+K-means algorithm has a lower clustering error rate and can successfully identify all 7 strata; (2) Considering the training time, RF is the optimal algorithm for this project due to its brief training time of only 3.808 s, coupled with high predictive performance. The research outcomes outlined in this paper offer a promising methodology for identifying stratigraphic boundaries during shield operation.

To investigate the internal force and deformation response law and reinforcement effect of a shield tunnel reinforced by channel steel in a pit excavation, a self-developed “hydraulic loading system” is used to conduct a full-size test and numerical simulation analysis on a three-ring staggered-seam assembled tube sheet. The results show that the internal force response of the tube sheet on the excavation side of the pit is complex and sensitive, the internal force is transformed in the direction under different load levels, and the bearing capacity can be effectively increased by 62.5 % through the channel steel reinforcement; the channel steel fails due to weld cracking, and the nonstructural bonding surface is damaged by sliding; and the maximum reinforcing efficiency of the combination of the channel steel and steel plate reaches 45.8 %, making it an economical and reliable reinforcing program.

Masonry lined tunnel condition assessment is a predominantly manual process. It consists primarily of a visual inspection followed by a lengthy and subjective manual defect labelling process. There is therefore much potential for automation. Masonry spalling is a key indicator of a masonry tunnel’s condition. To obtain actionable detail about a tunnel’s condition, it is also necessary to determine the spalling severity, defined by the depth of spalling. This study presents an automated workflow to identify the depth of spalling from masonry tunnel 3D point cloud data obtained by lidar. Firstly, a tunnel point cloud is unrolled using a cylindrical projection and the points are rasterised into a 2D image taking pixel values of the offset of each point from the cylinder. Then, a 2D U-Net pretrained on both real and synthetic masonry lining data, is used to segment masonry joint locations to isolate individual blocks. A separate U-Net is used to segment areas of masonry damage and data obstructions, which are then masked out before a surface plane representing the theoretical undamaged surface location is fitted to each masonry block from the remaining points. This allows the depth of spalling to be measured directly. As a result, this method can automatically determine the depth of spalling despite the curved and often deformed nature of a masonry tunnel profile. Experiments show results competitive with those obtained by human assessors.

The horizontal displacement and bending moment of piles due to adjacent shield tunnelling with a large longitudinal slope were investigated. An analytical calculation method for the horizontal response of shield tunnelling to piles was presented, considering the included angle, the tunnel-soil-pile interaction, and the shielding effect of the pile group. A new formula for soil horizontal deformation was derived by combining the cutterhead thrust force, the frictional force between the shield and soil, the grouting pressure and the soil loss, and the pile response was calculated as it was subjected to the generated ground displacement. The reliability of the analytical method was verified by the existing analytical solution, field monitoring data, and numerical simulation results. A parametric analysis of the longitudinal slope angle, shield tunnelling parameters, and soil modulus was conducted to assess their influences on tunnelling-induced pile deflection and bending moment. Finding that the increase in the longitudinal horizontal response of the pile is more prominent before the shield arrives at its side and the instant peak values of the horizontal response of the pile increase with increasing longitudinal slope angle. As the shield arrives at the pile side, the increase in the longitudinal horizontal response of the pile reaches the maximum value, and the influence of changes in the longitudinal slope angle on the horizontal response of the pile is not significant. The transverse horizontal response of the pile changes more after the shield passes through it and shows an increasing trend, the peak value of the transverse horizontal response of the pile is nearly 1 time that of the shield arriving at its side with passing through it of 20 rings. The changing trend of the horizontal response of the pile with increasing longitudinal slope angle after the shield passes the pile is opposite to that before arriving at its side. The cutterhead thrust force and the shield shell friction force are suggested to be positively correlated with the grouting pressure to reduce pile deformation. The horizontal response of piles caused by the shield tunnelling load decreases with increasing longitudinal slope angle after the shield passes through. The horizontal response of the pile is more significantly affected by the change in the longitudinal slope angle of shield tunnelling in the stratum with a smaller soil elastic modulus.

The high rock temperature and hot water influx in the surrounding area of the tunnel construction cause an excessively humid and environment high temperature inside the excavated area of the tunnel, necessitating urgent investigations into the environmental characteristics coupled with these factors and optimizing the control scheme of the construction environment. The on-site data of the tunnel temperature, humidity fields, and external environmental parameters have been collected, along with statistical analysis of the amount of the heat in the resource at the excavation face during the construction period. Subsequently, a three-dimensional numerical model coupling with high rock temperature, hot water, and ventilation was established. Based on the site monitoring data comparison, it was found that the average errors of temperature and humidity field values in the numerical simulation were 4.7 % and 7.1 %, respectively. By introducing the Heat Index (HI), the tunnel environmental characteristics under different conditions were analyzed, showing a linear relationship between the maximum HI at the excavation face and the two following features which are: the temperature-humidity of the input wind, and the hot water quantity. At the same time the air volume exhibited a quadratic relationship. Furthermore, by utilizing multivariate functions to fit the research results, the results show that the maximum HI under various conditions can be predicted. In addition, ultimately establishing an environmental safety assessment model was effective in incorporating multiple factors like input wind temperature, humidity, air volume, and hot water quantity for construction tunnels.

Ventilation is the primary solution for addressing elevated temperatures, humidity, and pollution with underground environments. Underground natural ventilation stands as a historical and promising strategy to reduce energy consumption and diminish reliance on mechanical ventilation. This study integrates aboveground and underground environments to enhance underground natural ventilation in the tropics. Initially, the study employed field measurements and computational fluid dynamics simulations to compare the natural wind environments and architectural designs of enclosed and detached condominiums in Singapore. The results demonstrate a strong correlation between the aboveground and underground wind environments in the enclosed condominium, revealing distinctive airflow patterns conducive to ample ventilation. Conversely, the basement of the detached condominium lacked natural ventilation and had tenuous connections to aboveground wind environments despite incorporating numerous skylights and side windows. Subsequently, the study proposes optimising architectural designs for row buildings through cross ventilation, sunshade, and greenery inspired by the architectural design of the enclosed condominium. Moreover, this study suggests some design strategies applicable to the tropics in hot and humid climates. These findings help architects and engineers create sustainable, natural, airy underground spaces.

Data visualisation is broadly utilised to aid in presenting complex information, facilitating decision-making, and enhancing operational efficiency in the mining sector. However, due to the extensive utilisation of CAD files and the complexity and difficulty of converting 2D drawings into 3D models, it is challenging to realise (near) real-time 3D data visualisation in mining applications. The difficulties are including site drawing complexity, lack of standardisation, time-consuming cleaning, and imperative manual intervention. This paper addresses these challenges by focusing on an automatic, data-driven approach for 3D visual model development in mining, with an emphasis on lifetime support and sustainability. Therefore, we introduce standardised visual model data diagram and proposed conversion workflows to leverage digitised 2D drawings in automatic 3D visual model development. Moreover, to improve visualisation efficiency and facilitate visual analytics construction in mining, this paper also proposes a 3D tile index methodology for efficient visual model reconstruction and generic production data integration. To ensure lifetime support and sustainable development in visualisation, we propose two model expansion schemes: one based on dxf file-driven model development, and the other one is interaction-oriented 3D model design and development, which the two schemes share the same data exchange and conversion workflows. Furthermore, to facilitate data fusion among various datasets, we also provide insights into revealing spatial–temporal patterns among multimodality data by real-time visualisation. These advancements aim to propel the field of underground mining visualisation, offering significant insights into enhancing the efficiency and safety of mining operations.

During shield tunneling through existing steel reinforced concrete structures, superstructure deformation is an important parameter that reflects the disturbance degree of engineering construction to existing structure. Precisely predicting structural deformation can help engineers adjust shield machine operational parameters and ensure the success of the project. There has been no attempt to study the feasibility and applicability of machine learning for predicting structural deformation when shield machine cut through existing structure. To address this problem, this paper proposes a novel hybrid model (DSGCN-TCN), combining dynamic spatial graph convolutional network (DSGCN) and temporal convolutional network (TCN), to predict structural deformation. First, dynamic adjacency matrix is constructed based on correlation coefficient and attention mechanism to describe the dynamic change of irregular graph structure. Then dynamic adjacency matrices and feature matrices as the input of the GCN model to extract the dynamic spatial feature of structural deformation data. Followed by TCN and attention layer to capture the temporal correlation of structural deformation data. Finally, the prediction performance of the proposed method is verified using measured data from practical engineering. The experiment results show that compared with the selected baseline models and sub-models, the proposed model can predict the structural deformation more accurately.

With the rapid urbanization and infrastructure development, there is a growing demand for the construction of super-large-diameter tunnels in China. As a result, understanding the impact of tunneling on soil behavior is becoming increasingly important. This paper provides a detailed case study on the construction of a super-large-diameter shallow-buried shield tunnel in Zhuhai, China, with a special focus on the soil-carrying effect. This phenomenon, identified for the first time in shield tunneling, is triggered by the covering of solidified grouting on the shield shell during tunneling and results in a distinct pattern of soil deformation. The study explores the mechanism and disturbance characteristics of the soil-carrying effect in shield tunneling. It also examines the causes of the mortar covering that triggers this effect. Through soil monitoring data, the disturbance characteristics of the soil-carrying effect in this project are demonstrated from three aspects: longitudinal ground displacement, settlement trough, and deep horizontal displacement. The study found that when the excavation width becomes insufficient to support the departure of the shield shell and mortar covering, the overlying soil gets pushed forward with the shield tunneling progression. This leads to two distinct failure faces in the overlying soil along the longitudinal axis and poses significant challenges in controlling the volume of synchronous grouting. The monitored data from the project revealed a “wave” disturbance on the ground during shield tunneling, accompanied by passive uplift and horizontal spreading and collapse of the surrounding soil during the shield passage. To address the soil-carrying effect, the primary treatment proposed involved the installation of multiple rows of vibrating steel sheet piles. These piles help loosen and block the solidified mortar, facilitating its removal from the shield shell. Furthermore, a new type of single-liquid slurry that extends the initial setting time was introduced to prevent the reappearance of mortar covering. The effectiveness of the proposed measures was verified through subsequent monitored ground displacement. The case presented can provide warning and reference for subsequent super-large-diameter shallow-buried shield tunneling projects.