Tunnel Engineering Construction Research Articles

Risk early warning model of tunnel engineering based on computer vision and CNN

Abstract Safety management in tunnel construction is important to ensure the safety of construction personnel and equipment. This paper proposes a tunnel engineering risk early warning model based on computer vision and convolutional neural network (CNN), aiming at realizing real-time monitoring and risk early warning of the construction site using modern image processing technology and deep learning algorithm. Many image data of tunnel engineering construction sites were collected, and the data were preprocessed and marked. Then, the paper designs a depth CNN model for feature extraction and risk identification of construction site images. Through the performance evaluation of the model on the training set and test set, the effectiveness and feasibility of the model in risk early warning are verified. The experimental results show that the proposed model achieves high accuracy, recall, and F1 score on the test set, which is superior to the traditional method based on image features and artificial rules. At the same time, we analyzed the prediction results of the model on the actual construction site images. We found that the model can effectively identify different risk factors and has strong generalization ability and practicability. To sum up, this study provides a new technical means and solution for the safety management of tunnel engineering, which has important theoretical and practical significance.

Research on the performance and application of waterproofing materials in tunnel engineering

Abstract With the rapid development of highway transportation, the volume and construction difficulty of tunnel engineering have been increasing year by yea. Many engineering problems are difficult to solve, among which leakage is one of them. Tunnel waterproofing materials are an important component of controlling leakage and ensuring the safety and reliability of tunnel engineering. This paper provides the types, characteristics, and applications of tunnel waterproofing materials in tunnel engineering. The classification of tunnel waterproofing materials is introduced, including grouting materials, geotextile materials, and waterproofing board materials. Then, the characteristics of each type of material are elaborated in detail, including durability, constructability, and environmental friendliness. Finally, combined with actual engineering cases, the application of these tunnel waterproofing materials in tunnel engineering is discussed. This paper aims to provide a reference for the design and construction of tunnel engineering, and to provide a theoretical and practical basis for the research and application of tunnel waterproofing materials.

Forward and inversion approach for direct current resistivity based on an unstructured mesh and its application to tunnel engineering

AbstractThe accurate identification of water‐bearing structures is urgently required for the safe construction of tunnel engineering. Currently, the direct current resistivity method is an effective method for detecting water‐bearing structures in tunnels. In the advanced detection of the direct current resistivity based on the finite element method, the traditional hexahedron mesh performs poorly for the discretization of models of complex tunnel structure sections such as horseshoe‐shaped and round sections. Therefore, this study adopts unstructured grid generation technology combining tetrahedra and hexahedra to achieve more accurate modelling of complex structures, such as round and horseshoe‐shaped sections, and establishes a forward modelling method of the direct current resistivity in tunnels based on an unstructured mesh. The maximum error between the numerical simulation and theoretical results for an infinite tabular body in full space is less than 0.8%. It is more complicated to calculate the sensitivity matrix and model constraint term for the inversion region containing two types of grid than for one. For this purpose, the sensitivity matrix of different types of grid areas is calculated, a model constraint term based on the dual constraints of volume and distance is constructed, and finally, a partitioned domain‐weighted least‐squares inversion method based on an unstructured mesh is proposed. Synthetic examples of typical water‐bearing structures are analysed, and the results show that the proposed forward and inverse methods of the direct current resistivity in tunnels based on an unstructured mesh can effectively capture the position and morphology of the water‐bearing structure. Finally, an on‐site application was conducted in the Yellow River Diversion Project in central Shanxi. The proposed method could effectively identify the water body in front of the tunnel face and guide the on‐site construction of the project. These results can improve the interpretation of the direct current resistivity data in tunnels and play a positive role in promoting the use of the direct current resistivity method to prevent and control water‐inrush disasters in tunnels with complex structures.

Self-supervised learning waveform inversion for seismic forward prospecting in tunnels: A case study in Pearl River Delta Water Resources Allocation Project in China

Tunnel and underground engineering construction often encounter unfavorable geology, leading to disasters such as water and mud inrushes and landslides. To prevent geologic hazards, it is important to look ahead and predict the location and distribution of adverse geology ahead of the tunnel face. This process is known as seismic forward prospecting in tunnels, and it typically requires an accurate calculation of velocity. Seismic waveform inversion methods based on deep learning have demonstrated potential in estimating velocity from synthetic seismic data. However, the superiority of these methods over traditional ones on field data is still an area of active research. Here, the Pearl River Delta Water Resources Allocation Project in China is used as an example to develop a self-supervised learning waveform inversion method for building a reliable velocity distribution in front of the tunnel. By introducing the background velocity as large-scale information and implementing multiscale loss functions, the previous self-supervised learning inversion method on synthetic data is improved. In addition, the corresponding network-based workflow for field data is developed. To demonstrate the effectiveness of our method, a comparison is conducted with practical tunneling exposure, for which the low-velocity zone corresponds with the fault-fractured zones and the water-flowing zones. This indicates that the results obtained from our method can be used as geologic guidance for safe tunneling practices. In the end, the applicability and disadvantages of our deep-learning inversion method for seismic forward prospecting in tunnels are discussed.

Experimental investigation on identification of lithologies and layered rock interface based on drilling vibration response

The rapid and accurate acquisition of lithologies and rock interfaces is an important prerequisite for guiding the development of oil gas and solid mineral resources as well as the construction of tunnel engineering. However, few studies have been conducted to identify the lithologies and rock interfaces using drilling information. The author used a drilling test platform and an integrated drilling information acquisition system to conduct drilling vibration tests on rock samples of limestone, sandstone, and coal with different lithologies and rock strengths. The test results indicated the following: 1) The drilling vibration response can characterize the properties of the lithology and rock strength and can be used as a key index to distinguish the lithologies and rock layer interface. 2) There were substantial differences in the drilling response (WOB and torque) and vibration response (vibration velocity, acceleration, and amplitude) of the single rock sample. The mean axial vibration velocities of coal, limestone, and sandstone were 5.6, 7.3, and 13.9 mm/s, respectively. The mean axial vibration accelerations were 9.2g, 32.3g, and 13.1g, respectively. The mean amplitudes of the rock surface were 402.6, 588.3, and 2003.8 μm, respectively. The mean weight on the bit was 1.3, 2.6, and 3.5 kN,1 respectively, and the mean torque was 12.3, 25.1, and 33.6 N m, respectively. 3) For the combined rock samples, the drilling and vibration responses of the layered rock interface showed an evident surge. 4) The rock strength affected the drilling and vibration responses. The stronger the rock, the higher was the drilling response (WOB and torque), higher the vibration acceleration, and lower the vibration speed and amplitude. The drilling vibration response displayed a high sensitivity to rock strength. It could effectively characterize the strength characteristics of the rock to accurately identify the lithologies and layered rock interface.

Effects of nano-silica modification on early age hydration process in winter construction of tunnel engineering

Fast hardening and high early strength are crucial factors for concrete used in tunnel construction in cold regions. The incorporation of nano-silicate has been found to be an effective method for improving the properties of cement-based materials at an early age. Thus, the objective of this paper is to investigate the nano-modification effects of different nano-silica contents on the hydration process, mechanical properties, and hydration products of cement cured in a low-temperature environment. The effects of various nano-silica concentrations, including 1%, 2%, 3%, and a high dose of 6%, on the properties of the concrete were investigated. According to the test results, the optimal quantity of nano-silica plays a crucial role in determining the properties of concrete. The effects of nano-silica on the hydration of C3A were found to dominate the cement hydration process at an early age. The incorporation of nano-silica led to a significant improvement in the dissolution rate of anhydrite and the reaction rate of the C3A renewal, which may be responsible for the gain in early strength of concrete. However, an excessive amount of nano-silica could negatively affect the hydration process of the alite and C3A, as evidenced by the total heat generated during the silica and aluminate reactions. The XRD patterns further confirmed these results.

Analytical method for new tunnel crossing pile foundation of existing bridge: a case study

This paper describes an analytical method for investigating the tunnel–pile interaction for new tunnels crossing the pile foundation of the Shenzhen Bay Bridge, with a case study using a cavity expansion-based model. The three-dimensional analytical model developed in this study evaluates the ground deformation and pile response induced by the construction of tunnels for the two Metro #13 lines and the Wanghai Road tunnel, and assesses the effectiveness of mitigation measures such as ground stabilisation and isolation walls. The study reveals significant vertical displacement and surface settlement caused by the Wanghai Road tunnel, and horizontal deformation and bending moments in specific pile foundations. The results show that reinforcement measures can effectively control formation deformation disturbance, and metro jet system isolation walls can limit horizontal and vertical displacements caused by excavation. To ensure the safe operation of the Shenzhen Bay Bridge, the study highlights the importance of comprehensively evaluating the safety of shield crossing schemes. The proposed analytical method could also serve as a pre-design tool and reference for optimising tunnel construction, providing valuable guidance for future reinforcement schemes. In general, this study provides significant insights into the tunnel–pile interaction, which will be useful for bridge and tunnel engineering design and construction.

Exploring the Design and Practice of Ideological and Political Education in the Course of Tunnel Engineering under the Background of New Engineering Discipline: A Case Study of Hope College, Southwest Jiaotong University

Under the background of the new engineering discipline, talent cultivation requires not only intellectual education but also moral education. In response to the main issues concerning ideological and political education in the current new engineering discipline curriculum, this paper focuses on exploring the process of ideological and political construction in tunnel engineering. It highlights the necessity of curriculum-based ideological and political education and the exploration of ideological and political elements. These elements are cleverly integrated into the course design, and the effectiveness of the ideological and political practice in the curriculum is examined through an evaluation of teaching outcomes. The aim is to improve the educational effectiveness of the tunnel engineering construction course and provide valuable insights and references for the ideological and political construction in other engineering disciplines.

Distribution Pattern and Influencing Factors for the Temperature Field of a Topographic Bias Tunnel in Seasonally Frozen Regions

In seasonally frozen regions, highway tunnels are prone to shallow buried bias pressures near the inlet/outlet, which leads to highway tunnels not only bearing asymmetric loads, but also facing the threat of extreme weather. However, there is still no clear understanding of the temperature field for topographically biased tunnel in seasonally frozen regions at present. Taking the Huitougou tunnel of Hegang-Dalian expressway as the object, this paper uses on-site monitoring, theoretical analysis, and numerical simulation to study the distribution law and influence factors of temperature field for topographically biased tunnel in seasonally frozen regions. The numerical results of the temperature field are in good agreement with the on-site monitoring data, which verified the accuracy of this numerical model based on the aerodynamic principle, turbulence model, and wall function method. Meanwhile, the effect of different slope angle and overburden thickness on the temperature field of the tunnel is further analyzed. It is found that when the slope angle increases, the temperature field in the tunnel surrounding rock changes accordingly. The connecting area between the surface and the tunnel temperature field is deflected from arch crown to the arch shoulder of the tunnel, resulting in a large change in the temperature of the shallow buried side, while minor change in the temperature of the deep buried side. The freezing depth of surrounding rock decreases with the rising slope angle. As the overburden thickness gradually increases, the temperature field of the surface surrounding rock and the tunnel surrounding rock gradually change from mutual influence to non-influence. When the overburden thickness exceeds 15 m, a “isolated temperature zone” appears in the middle with a temperature of 6~7 °C, the temperature field of the tunnel surrounding rock is basically not affected by the surface air temperature. These results can provide important theoretical and engineering guidance for the evaluation, construction, and maintenance of tunnel engineering in seasonally frozen regions.

Experimental study of face stability for shield tunnels in sandy cobble strata of different densities

This paper aims to study the influence of relative density on the working face stability of shield tunnel in sandy cobble stratum. A series of geomechanical model tests were conducted for shield tunnels excavating through loose sample (LS), medium dense sample (MS) and dense sample (DS), respectively. Relative densities of LS, MS and DS are 0.35, 0.55, and 0.75. The method of continuous rotation of spiral excavators while shield excavators stop tunneling is adopted to simulate the instability of tunnel face. Experimental results effectively reveal the variation characteristic of vertical and horizontal earth pressure and lateral pressure coefficient of shield tunneling. The evolution of the failure zone and soil arch height of strata with different densities was explored. The failure area and collapse range obtained from the model test were compared with the existing method. The effect of relative density on the horizontal earth pressure in the instability stage of the tunnel face in the sandy cobble strata is greater than that of the vertical earth pressure. In addition, increasing the relative density can effectively increase the lateral pressure coefficient as well as the stability of the tunnel face. The existing methods have deviations in analyzing the instability area of the tunnel face in the sandy cobble strata with different relative densities. The research in this paper provides a reference for the construction and theoretical analysis of sandy cobble strata shield tunnel engineering.

Analytical solution for the temperature field of an elliptical tunnel in cold regions

For the existing tunnels, only few of them are circular sections, the most of them are approximately elliptical sections. Correspondingly, the existing analytical solution researches basically focus on the circular tunnels. To study the distribution law of temperature field of an elliptical section tunnel in cold region, the conformal mapping method is adopted in this paper. Through the conformal mapping method function, a circular function in complex variable space is transformed into an elliptic function in Euclidean space, and then the analytical solution of variation law of temperature field of elliptic section tunnel is derived based on the analytical solution of temperature field of a circular tunnel in complex variable space. An analytical solution example for the temperature field distribution of an elliptical section tunnel in cold region is derived, the calculation results show that: (1) Sizes and variation rates of elliptic freezing surface are greatly affected by freezing time. At the outset, the elliptic freezing surface changes relatively quickly with the increase of freezing time, but the elliptic freezing surface changes relatively slowly when the freezing time is relatively long. (2) The temperature values on a certain elliptic cross section surface decrease with the increase of freezing time. (3) The ratio of the major semidiameter to minor semidiameter of elliptic freezing surfaces is getting closer to 1 with the increase of freezing time. It is also said that the elliptic freezing surface changes from ellipse to circle with the freezing time increasing. By comparing the analytical solution with the numerical solution, it is found that the analytical solution proposed in this paper has high accuracy. This study can provide important theoretical and engineering guidance for the evaluation, design, construction and maintenance of tunnel engineering in seasonally frozen soil regions and permafrost regions, and this study also has important scientific value.

Nano-modification effect on the pore characteristics and the water multiscale transport properties of concrete in winter construction of tunnel engineering

Seepage has become the dominant damage that affected tunnel stability. Although drainage and the waterproofing system are frequently employed in seepage tunnels, the poor performance of shotcrete is still an inducement for the waterproofing system failure. Further, the frost damage caused by seepage becomes more pronounced when tunnel construction locates in cold region environments. Therefore, the objective of the study is to explore the nano-modification effects on the water multiscale transport behaviors of concrete in winter construction environments. Firstly, the pore characteristics of the hydrated cement were experimentally determined by the mercury intrusion porosimetry (MIP) test. The meso-structures of concrete were obtained via the X-ray computed tomography (CT) test. Secondly, the fractal analysis was conducted to derive the permeability of the hydrated cement based on the capillary model with the interaction of solid and fluid molecules considered. Then, the permeability distribution of concrete was calculated by combining test results at the micro-scale and that at the meso-scale. Finally, the unified multiscale simulations based on the generalized Lattice Boltzmann method (GLBM) were conducted to obtain the permeability of all groups. The water transport process of concrete on the meso-scale was simulated by considering the influence of micro-structures. The permeability tests were conducted to verify the simulation results. Results indicated that the addition of nano-materials can markedly increase the complexity of the pore structure and decrease the porosity, thereby enhancing the impermeability of concrete.

Application of Artificial Freezing Method in Deformation Control of Subway Tunnel

The metro tunnel construction mainly passes through the downtown area, including ground buildings, infrastructure, underground pipelines, existing subway lines, and station floors. However, it is very difficult to control the ground deformation, especially in the water-rich soft ground or in the tunnel engineering construction with strict requirements for surface settlement control. The traditional stratum reinforcement method may not meet the engineering needs. In this case, the artificial freezing method (AFM) provides a solution for such engineering problems. This paper summarizes the basic principle and characteristics and application scope of AFM, and compared with the other three stratum reinforcement methods, AFM has better effect in controlling surface displacement and vault settlement, while grouting method, pipe shed method, and pipe curtain method have absolute advantages in controlling surface uplift. Then, through engineering examples, the reinforcement effect of AFM in the four aspects of subway connecting passage, shield inlet and outlet, interval tunnel, and damage repair is introduced. Through analysis, it is found that the reinforcement effect of AFM in water-rich weak stratum is very good. Finally, the future development of AFM is prospected in order to provide some experience and guidance for the follow-up research.

Influence of a Landslide on a Tunnel in Loess-Bedrock Ground

By combining model testing and numerical simulation, this paper focuses on the influence of landslides on tunnels in loess-bedrock strata by using the perfect landslide–tunnel system (LTS). A mechanical test and simulation (MTS) system was used to provide thrust for loading and unloading the trailing edge of the slope. A Particle Image Velocimetry (PIV) and 32 cluster strain gauges were adopted to monitor the deformation of the tunnel structure and landslide soil, and the sliding surface, respectively. By means of a numerical simulation, the deformation characteristics of a tunnel crossing loess-bedrock strata are comprehensively described. The influence of a cyclic load on the mechanical behavior and displacement of the tunnel and sliding surface is discussed in detail. The experimental results show that the thrust required for the first landslide is the largest, during multiple loading and unloading. With the increase in loading and unloading time, the sliding thrust gradually decreases and eventually remains stable. The landslide presents a progressive failure mode. There is a stress concentration in the upper part of the tunnel, which causes the secondary sliding phenomenon. The deformation of the sliding surface mainly occurs in the upper soil of the tunnel. The deformation direction of the tunnel is consistent with the sliding direction, and the deformation of the sliding surface mainly occurs in the soil above the tunnel. When disturbed by an external force, the tunnel deforms downward, and, when unloaded, the tunnel has a small rebound deformation. However, with the increase in loading–unloading times, the rebound deformation of the tunnel gradually decreases, and the permanent deformation gradually accumulates until the tunnel fails. The research results can provide reference for the construction and protection of tunnel engineering in loess regions, and have reference value for the control of tunnels crossing landslides.

Brief Analysis of Excavation and Collapse Treatment of Water Conservancy Tunnel Engineering Construction

Brief Analysis of Excavation and Collapse Treatment of Water Conservancy Tunnel Engineering Construction

Seismic Stability of 3D Tunnel Face considering Tensile Strength Cut-Off

Earthquakes can have a very adverse effect on tunnel excavation. The Mohr-Coulomb failure criterion is modified by introducing tensile strength cut-off, which allows nonlinear strength reduction of soil under tensile conditions, and kinematic analysis of tunnel face subjected to the earthquake is carried out. The pseudo-dynamic method is adopted to simulate the earthquake with the acceleration varying with time and space, improving the accuracy of the simulation. The external power and internal energy dissipation rate are equal to obtain the expression of tunnel face support pressure under the limit analysis framework. And the most unfavorable tunnel face support pressure is optimized by using the method of exhaustion. Compared with other research results, the validity of this method is proved. The influence of soil parameters and pseudo-dynamic parameters on the critical support pressure is revealed by further parameter analysis. Finally, this study provides an effective reference for seismic design of tunnel engineering construction.

Investigation and application of a high performance grouting material in water-rich silty fine sand stratum

Grouting reinforcement of water-rich silty fine sand stratum is a key and difficult problem in the construction of tunnel and underground engineering. In this paper, a kind of high-performance grouting material (DS grout) for water-rich silty fine sand stratum was prepared by using sodium silicate as the base material and diacid ester as the curing agent. The results show that the DS grout has adjustable setting time, high strength and high durability. The reaction mechanism of sodium silicate and curing agent was studied by infrared spectroscopy (IR) and scanning electron microscope (SEM). The acid generated from the hydrolysis of diacid ester reacted with sodium silicate solution and polymerized to generate silica gel. Through the grouting model experiment, the grouting effect of DS grout and phosphate-sodium silicate grouting material was compared. In addition, DS grout was used to reinforce the face of tunnel in water-rich silty fine sand stratum. The results show that DS grout can effectively penetrate into water-rich silty fine sand stratum and form high strength sand solidification body.

Influence of Arch Foot Defect of Primary Support on Mechanical Behaviors of an Arch Frame in Underground Tunnels

During the blasting excavation of the large-span tunnels, the instability of the blasting caused the overexcavation phenomenon, making the grille arch difficult to land completely in the primary support of the tunnel, thus forming an arch foot defect. In order to reduce the security issues of tunnel engineering construction and scientifically evaluate the influence of arch foot defects on the force performance of the overall structure of the arch frame, combining the Qingdao Metro long-span hard rock tunnel project, this paper designs two grille arch test sections with arch foot defects and one conventional section to carry out field tests. Combining with FLAC3D numerical simulation, the results of the study were used for analyzing the stress characteristics of arch foot defect grille arch in the primary support of the tunnel. The results indicated that (1) the arch foot of conventional section arch frame is subjected to the force transferred from the upper part and the deformation pressure of surrounding rock within the arch foot range, and the upper transfer force borne by the arch foot mainly comes from the deformation of arch waist. (2) When the arch frame has arch foot defects, the deformation of surrounding rock at the arch foot and the deformation transferred from the upper part mainly depend on the shotcrete, thus resulting in the increase of shotcrete strain. (3) Anchoring bolt and shotcrete can integrate the grid arch with the surrounding rock, thus bearing local loads in the arch crown, arch waist, and shotcrete. (4) The numerical calculation of arch frame with arch crown, arch waist, and arch foot defects claims that the force reduction of the arch frame caused by the arch foot defect was the most obvious, and the calculation results were consistent with the actual project.

Influence of freeze–thaw cycles and shear rate on sandstone-concrete interfacial bond strength: Experiment and degradation model

In the construction of tunnel engineering in cold regions, the good bonding between shotcrete and surrounding rock is the premise to ensure the stability of engineering support. However, the interface bonding between shotcrete and surrounding rock will be degraded by the freeze–thaw (F-T) cycles and the blasting vibration generated in the construction process of drilling and blasting method. Therefore, Firstly, the interfacial shear mechanical properties tests with different F-T cycles (i.e., 0, 5, 10, 15, and 20) and different shear rates (i.e., 0.25, 1.0, 2.0 and 4.0 mm/min) were carried out. Secondly, the effects of F-T cycles and shear rate on the variation of stress-displacement curve, the peak strength and interfacial failure mode of sandstone-concrete interface were analyzed. Finally, an interface degradation model for evaluating the effects of the above two factors was proposed. The primary conclusions are as follows: (1) With the increase of F-T cycles, the interfacial peak strength decreases gradually, while the adhesion area of sandstone on the concrete side increases gradually. The interfacial shear failure caused by F-T actions mostly occurs on the sandstone side. (2) With the increase of shear rate, the peak strength and the shear stiffness of sandstone-concrete interface increase gradually. The shear deformation of the interface is mainly reflected in the damage form of “abrasion, extrusion and shearing” between particles. (3) The greater the strength difference of rock materials on both sides, the side with weaker rock strength is the key area for interfacial F-T deterioration and debonding. (4) A new interface degradation model of rock-concrete interface shear strength considering F-T actions and shear rate was established, and the reliability of the theoretical model was verified. The study provides experimental and theoretical reference for exploring the interfacial debonding evolution mechanism of shotcrete in tunnels in cold regions.

Intelligent rating method of tunnel surrounding rock based on one-dimensional convolutional neural network

Accurate prediction of surrounding rock grades holds great significance to tunnel construction. This paper proposed an intelligent classification method for surrounding rock based on one-dimensional convolutional neural networks (1D CNNs). Six indicators collected in some tunnel construction sites are considered, and the degree of linear correlation between these indicators has been analyzed. The improved one-hot encoding method is put forward for transforming these non-image indicators into one-dimensional structural data and avoiding the sampling error in the indicators of surrounding rock collected in the field. We found that the 1D CNNs model based on the improved one-hot encoding method can best extract the features of surrounding rock classification indicators (in terms of both accuracy and efficiency). We applied the well-trained classification model of tunnel surrounding rock to a series of expressway tunnels in China, and the results show that our model could accurately predict the surrounding rock grade and has great application value in the construction of tunnel engineering. It provides a new research idea for the prediction of surrounding rock grades in tunnel engineering.