3D Tunnel Research Articles

Automation and digitalisation of the geological documentation in tunnelling

AbstractIn tunnelling, the geological documentation comprises the daily recording and processing of various data for continuously assessing the geological–geotechnical conditions on‐site. One of the core tasks is the documentation of the tunnel face area. With Geodata's Tunnel Mapper, a new measuring system is presented enabling a highly automated data acquisition and the processing of a geo‐referenced three‐dimensional (3D) tunnel face model. Versions of the measuring system for both conventional and mechanised tunnelling have been developed. From the 3D model, high‐quality digital products as well as geometric and geological parameters can be derived, which serve as a basis for decisions on‐site. The data can then be integrated into the geological information system TUGIS.NET of Geoconsult, merged there with other data and further (geologically) evaluated, analysed and visualised. A spatial model that has been interpreted and quantified by the geologist can be established and used for target/actual comparisons and forecasts. The model can be transferred into building information modeling (BIM)‐compatible data structures for integration into an overall BIM model of the project. The further automation and digitalisation of the geological documentation and the full documentation (geometry and geology) of the face area are achieved in the interaction of the systems mentioned.

APPLICATION OF RGB-D SLAM IN 3D TUNNEL RECONSTRUCTION BASED ON SUPERPIXEL AIDED FEATURE TRACKING

Abstract. In large-scale projects such as hydropower and transportation, the real-time acquisition and generation of the 3D tunnel model can provide an important basis for the analysis and evaluation of the tunnel stability. The Simultaneous Localization And Mapping (SLAM) technology has the advantages of low cost and strong real-time, which can greatly improve the data acquisition efficiency during tunnel excavation. Feature tracking and matching are critical processes of traditional 3D reconstruction technologies such as Structure from Motion (SfM) and SLAM. However, the complicated rock mass structures on the tunnel surface and the limited lighting environment make feature tracking and matching difficult. Manhattan SLAM is a technology integrating superpixels and Manhattan world assumptions, in which both line features and planar features can be better extracted. Rock mass discontinuities including traces and structural planes are distributed on the inner surface of tunnels, which can be extracted for feature tracking and matching. Therefore, this paper proposes a 3D reconstruction pipeline for tunnels, in which, the Manhattan SLAM algorithm is applied for camera pose parameters estimation and the sparse point cloud generation, and the Patch-based Multi-View Stereo (PMVS) is adopted for dense reconstruction. In this paper, the Azure Kinect DK sensor is used for data acquisition. Experiments are proceeded and the results show that the proposed pipeline based on Manhattan SLAM and PMVS performs good robustness and feasibility for tunnels 3D reconstruction.

Parametric study of tunnel analysis in clay shale on short term and long-term conditions using finite element method

This study aims to determine the characteristics and classification of clay shale in West Java and their implications for tunnel stability under short and long-term conditions using the finite element method. Data were collected from projects in West Java containing clay shale spread over four rock formations, namely Cihoe (Tpc), Subang (Tms), Cantayan (Mtts/Mttc), and Jatiluhur (Tmj). Each formation has varying mechanical and engineering properties. The value of SPT from Cihoe formation can be categorized in three conditions, SPT < 40, SPT 40-60, and SPT > 60 for fully, highly to moderately, and slightly weathered, respectively. Meanwhile, the value of SPT of Subang formation can be categorized in two conditions, SPT < 60 and SPT >60 for fully and highly weathered, respectively. The data collected were analyzed to determine the Mohr-Coulomb (MC) and Hardening Soil (HS) parameters for Plaxis modeling. The model applied three variations of overburden thickness between 3 times, 6 times, and 9 times the tunnel diameter (3d, 6d, and 9d respectively). The greater the overburden thickness, the lower the surface deformation. The HS model gives better results than the MC model because it considers non-linearity. The minimum effective parameters needed to support tunnel during construction to meet the allowable deformation for 3d overburden conditions and the particular reinforcement system are c' 53kPa, ϕ' 28°, and E'50ref 30,000 kPa. Long-term conditions possess lower stability than short-term, while prolonged deformations increase after construction and provide a rise in tunnel lining stress that needs to be considered in the design stage. The application of 2D tunnel modeling needs to be carefully analyzed, thereby representing the behavior of a continuous or 3D tunnel structure.

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.

NIKE BLUETRACK: Blue Force Tracking in GNSS-Denied Environments Based on the Fusion of UWB, IMUs and 3D Models.

Blue force tracking represents an essential task in the field of military applications. A blue force tracking system provides the location information of their own forces on a map to commanders. For the command post, this results in more efficient operation control with increasing safety. In underground structures (e.g., tunnels or subways), the localisation is challenging due to the lack of GNSS signals. This paper presents a localisation system for military or emergency forces tailored to usage in complex underground structures. In a particle filter, position changes from a dual foot-mounted INS are fused with opportunistic UWB ranges and data from a 3D tunnel model to derive position information. A concept to deal with the absence of UWB infrastructure or 3D tunnel models is illustrated. Recurrent neural network methodologies are applied to cope with different motion types of the operators. The evaluation of the positioning algorithm took place in a street tunnel. If a fully installed infrastructure was available, positioning errors under one metre were reached. The results also showed that the INS can bridge UWB outages. A particle-filter-based approach to UWB anchor mapping is presented, and the first simulation results showed its viability.

Na3V2-xFex(PO4)2O2F: An advanced cathode material with ultra-high stability for superior sodium storage

Searching a suitable electrode material is one of the key issues of Sodium-ion batteries (SIBs) for the large-scale applications. Sodium-rich Na3V2(PO4)O2F (NVPOF) with a 3D tunnel structure is considered to be the promising cathode material for SIBs owning to the advantage of its high operating voltage, andstable structure, and good thermal stability. Nevertheless, the inferior reaction kinetics and unsatisfied sodium storage behavior resulting from its low electron conductivity hinder its further practical application. Here, Na3V2-xFex(PO4)2O2F microcuboids were synthesized via iron partially replacing V atom sites of Na3V2(PO4)2O2F by a simple hydrothermal method. Benefiting from the intrinsically improved electronic conductivity and enhanced charge transfer kinetics, Na3V1.85Fe0.15(PO4)2O2F (NVFPOF) with 15 wt% doping concentration shows an initial capacity of 137.2 mAh g−1 at 1C, which is about 31% higher than that of NVPOF. In addition, a full cell based on NVFPOF cathode and Hard carbon anode showed 82.3% capacity retention even after 100 cycles at 0.4C. Moreover, iron atoms can be used as the pillar of the host structure to buffer deformation and effectively alleviate the volume change (less than 1.05%) upon cycling, showing 86.5% capacity retention at 20C after 1000 cycles. The results provide an effective and simple way to construct advanced cathodes for SIBs.

An encoder-decoder deep learning method for multi-class object segmentation from 3D tunnel point clouds

Discovering seepage is widely thought to be critical for maintaining the healthy conditions of the tunnel. Unfortunately, most of the seepage surveys are still manual with tedious, time-consuming, and inefficient as well as work-related physical injuries. To address this problem, this research proposes an encoder-decoder deep learning method combined with point cloud techniques for multi-class object segmentation, including seepage, from 3D tunnel point clouds. This method develops data processing and feature extraction techniques to perform normalization of 3D point clouds with full consideration of point features, followed by constructing voxels as input to the proposed encoder-decoder architecture for learning. In the training process, an optimal model is selected with a learning rate of 0.0001, a batch size of 256, and a voxel boundary of 8. Subsequently, the optimal well-trained model is applied to the testing set, achieving excellent performance. Comparisons with other state-of-the-art methods and four data processing strategies are conducted, demonstrating that the proposed method outperforms in segmenting large-scale 3D point clouds. Overall, the proposed method performs excellently, beneficially contributing to the multi-class object segmentation from 3D tunnel point clouds with great practical potential.

Stability Factors F c , F s , and F γ for Twin Tunnels in Three Dimensions

This paper aims to study the three-dimensional (3D) tunnel heading pressure of twin circular tunnels in a drained cohesive–frictional soil using a stability factor approach and finite-element limit analysis (FELA). The primary concept adopted will be the use of a conventional equation that is similar to the traditional bearing capacity factors (e.g., Nc, Ns, and Nγ) in Terzaghi’s bearing capacity equation. For various spacing ratios (S/D) between the tunnels, the stability of the tunnels is expressed in terms of nondimensional tunnel stability factors (e.g., Fc, Fs, and Fγ), which are functions of the depth ratio (C/D) and soil internal friction angle (ϕ). For conciseness, the results will be presented in charts and tables with the tunnel stability factors that used the rigorous FELA upper (UB) and lower bound (LB) solutions.

3D stability analysis of tunnel face with influence of unsaturated transient flow

The analysis of tunnel face stability is commonly implemented with the assumption that the soil is dry or fully saturated. However, many practical cases occur in partially saturated soils, and the unsaturated component of the shear strength warrants consideration for a more realistic solution. This paper extends the current understanding of the tunnel face stability, which, for the first time, incorporates the contributions of unsaturated transient flow into the analytical framework of the three-dimensional (3D) tunnel face stability. A closed-form describing the spatio-temporal variability of saturation, suction stress, and apparent cohesion was derived and introduced into the Mohr-Coulomb criterion to consider the unsaturated transient flow. Within the framework of the kinematic approach of limit analysis, the work rate balance equation including the unsaturated component was established based on a 3D horn-like failure mechanism. A parameter analysis concerning the hypothetical fine sand, silts, and clay was performed to study some parameters of interest. The results show that unsaturated transient flows play a positive role in reducing the required face pressure. The magnitude of the influence is controlled by factors including soil types, thickness of the soil layer, and infiltration time. Compared with neglecting the unsaturated effect, the reduction of normalized critical face pressure caused by transient flows can reach 16.22% in fine sands, 24.98% in silts, and 85.62% in clays. The results suggest that the contribution of unsaturated transient flow to clays, particularly in the early infiltration stage, should be considered. Findings of this work can provide an insight to quantitively capture the influence of the unsaturated transient infiltration and the resulting transient changes of the 3D tunnel face stability.

An improved 3D point cloud instance segmentation method for overhead catenary height detection

The function of a subway-tunnel catenary is to ensure the safe operation of a subway under high-speed conditions; hence, it plays an irreplaceable role in the subway system. However, owing to bad tunnel environments and repeated vibrations, catenaries can easily become deformed. To solve the above problems, this study proposes a new detection method, which applies the 3D-BoNet instance-segmentation model with a multi-scale grouping (MSG) structure and transfer learning to a 3D point-cloud tunnel dataset. Experiments show that the improved model can effectively segment the left and right tracks and the catenary of a tunnel. A comparative experiment shows that the proposed method improves the average accuracy (mPrec) by 3.8% under the classical index with an intersection-over-union (IoU) threshold of 0.5. Moreover, the computational efficiency is improved by 33.01%. This method has broad application prospects in the research field of 3D point-cloud instance segmentation.

Indium silicate with an imandrite-type structure.

This work reports the synthesis and characterization of novel zeolite-like indium silicate MS-2 (Minho-Sofia, solid number 2). The structure of this material is analogous to that of the mineral imandrite (Na6Ca1.5FeSi6O18), with In instead of Fe in the octahedral position. MS-2 is the first structurally confirmed indium silicate prepared under mild hydrothermal conditions and the only synthetic indium silicate related to the lovozerite mineral group. MS-2 (Na6.23Ca1.62In0.68Si6O18) exhibits significant indium deficiency in the octahedral position thus having the highest Si/In (8.8) ratio among the known indium silicates. The framework consists of occupationally disordered InO6 octahedra interconnected by 6-membered rings of [Si6O18] tetrahedra. The three-dimensional (3D) tunnel system is occupied by Na+ and Ca2+ charge-balancing ions. The low framework density (16.2 FC/1000 Å3) and high thermal stability (up to 900 °C) are comparable to other molecular sieves.

Establishment of a Coupling Model for the Prediction of Heat Dissipation of the Internal Combustion Engine Based on Finite Element

The aerodynamics and heat transfer performance in the rear-mounted automobile cabin have an important influence on the engine's safety and the operational stability of the automobile. The article uses STAR-CCM and GT-COOL software to establish the 3D wind tunnel model and engine cooling system model of the internal combustion engine. At the same time, we established a 3D artificial coupling model through parameter transfer. The research results show that the heat transfer coefficient decreases with the increase of the comprehensive drag coefficient of the nacelle. This shows that the cabin flow field has an important influence on the heat transfer coefficient. The mainstream temperature rise of the engine room increases with the increase of the engine load. It is proved that vehicle speed affects the amount of heat dissipation of the engine room internal combustion engine under certain load conditions. The article provides a more effective and fast calculation method for the research on the heat dissipation of the internal combustion engine and the optimization of the cooling system equipment.

Evaluation of Lidar-based 3D SLAM algorithms in SubT environment

Autonomous navigation of robots in harsh and GPS denied subterranean (SubT) environments with lack of natural or poor illumination is a challenging task that fosters the development of algorithms for pose estimation and mapping. Inspired by the need for real-life deployment of autonomous robots in such environments, this article presents an experimental comparative study of 3D SLAM algorithms. The study focuses on state-of-the-art Lidar SLAM algorithms with open-source implementation that are i) lidar-only like BLAM, LOAM, A-LOAM, ISC-LOAM and hdl graph slam, or ii) lidar-inertial like LeGO-LOAM, Cartographer, LIO-mapping and LIO-SAM. The evaluation of the methods is performed based on a dataset collected from the Boston Dynamics Spot robot equipped with 3D lidar Velodyne Puck Lite and IMU Vectornav VN-100, during a mission in an underground tunnel. In the evaluation process poses and 3D tunnel reconstructions from SLAM algorithms are compared against each other to find methods with most solid performance in terms of pose accuracy and map quality.

Research on Visual Management Technology of Tunnel Construction Process Based on BIM Technology

In order to achieve more efficient management of BIM technology in the field of tunnel construction, this paper took Zhuhai Dahengqinshan No. 1 Tunnel as the project background and studied the visualization management technology of tunnel construction process based on BIM technology. Firstly, we created the 3D geological model and tunnel BIM model by using Revit, 3dsmax, and other software. Secondly, the detailed design was carried out, and there was no gap in the model after the detailed design was checked by ABAQUS software. Then, we checked the problems between disciplines and conducted collision inspection in the model. Finally, we carried out the 4D construction progress simulation to solve the conflict between time and space in the whole life cycle of tunnel construction. The results revealed that the deepening design could optimize the design scheme of tunnel construction engineering. Collision inspection directly exposed problems such as unscientific site layout. 4D construction schedule management could not only realize the visualization of field construction process but also improve the quality of project management compared with traditional means. The research results provide technical experience for the visualization management of tunnel construction.

Stability Analysis of Pressurized 3D Tunnel Face with Tensile Strength Cutoff

The aim of this study is to propose an effective approach to evaluate the stability of a shield tunnel face with tensile strength cutoff by using the upper-bound limit analysis method. Based on the discretization and “point by point” techniques, two improved rotational failure mechanisms, namely the improved collapse failure mechanism and the improved blowout failure mechanism, are developed with the tensile cutoff for the first time. Based on these improved failure mechanisms, the critical collapse and blowout pressures of tunnel faces are then determined by using the upper-bound limit analysis method. The proposed method is then validated by comparisons with previous analytical solutions and numerical results, showing that the proposed method is an effective approach to evaluate the stability of shield tunnel faces. The influences of model parameters on the critical support pressures and the failure feature of the proposed mechanisms are finally presented.

3D reconstruction and automatic leakage defect quantification of metro tunnel based on SfM-Deep learning method

Various structural defects deteriorate tunnel operation status and threaten public safety. Current tunnel inspection methods face problems of low efficiency, high equipment expense, and difficult data management. Combining the deep learning model and the 3D reconstruction method based on structure from motion (SfM), this paper proposes a novel SfM-Deep learning method for tunnel inspection. The high-quality 3D tunnel model is constructed by using images taken every 1 m along the longitudinal direction. The instance segmentation of leakage in longitudinal images is realized using the mask region-based convolutional neural network deep learning model. The SfM-Deep learning method projects the texture of the images after defect recognition to the 3D model and realizes the visualization of leakage defects. By projecting the model to the design cylindrical surface and expanding it, the tunnel leakage area is quantified. Through its practical application in a Shanghai metro shield tunnel, the reliability of the proposed method was verified. The novel SfM-Deep learning method can help engineers efficiently carry out intelligent tunnel detection.

Coupled three-dimensional analysis of the progressive tunnelling-induced damage to masonry buildings: is it always worth it?

The development of urban mobility implies the construction of tunnels, often interacting with valuable masonry structures. It is thus necessary to develop rational and reliable procedures to estimate the potential excavation-induced damage, which imply the analysis of the related soil-structure interaction problem.Classical approaches to soil-structure interaction are often characterised by relatively simple schematisations for either one or both components of the problem, as, for example, springs for the soil or equivalent plates for the structure. Such simplified assumptions prove to be appropriate for conventional soil-foundation cases, while show all their limitations when tackling more complex problems, as those involving the excavation in the vicinity or beneath masonry structures. In such cases, the need for reliable prediction of the potential damage induced by construction activities on surface structures justifies the adoption of more advanced numerical approaches, based on realistic constitutive assumptions for both soil and masonry, together with an accurate modelling schematisation of the excavation process.This is what proposed in this paper, where a 3D Finite Element approach is adopted to realistically model the multidimensional and progressive nature of the excavation process, the strongly non-linear soil behaviour and the non-linear anisotropic response that characterises masonry structures, here included accounting for their 3D geometrical characteristics. All the analyses are carried out with reference to a sample masonry building founded on strip footings, interacting with a shallow tunnel in a typical London soil profile, already examined in the literature. Different configurations of the structure, considering the sole façade or the whole building, are examined. Also, different relative positions of the tunnel and the structure, in terms of skew angle and eccentricity, are considered. In all the analyses, the excavation is simulated either reproducing the whole three-dimensional advancement of the tunnel or through a simplified single-step analysis.A critical review of the deformation regimes and related plastic points patterns resulting from the different analyses point out in which cases it is necessary to accurately model the 3D tunnel advancement to detect the transient effects governing the onset of structural damage.

Measurement of Axial Strain of Geogrid by Optical Sensors.

In recent years, the technology of optical fibers has rapidly gained ground in many areas of science and industry, including the construction industry. In this article, the technology of optical fibers based on a fiber Bragg grating (FBG) was used to determine tensile forces acting in a basal reinforcement of a scaled down physical model, which included piled embankment and basal reinforcement. Installing FBG sensors on the geogrid made monitoring of axial strains possible, thus allowing determination of the behavior of the basal reinforcement of the piled embankment. On the basis of three tests performed on the physical model, numerical model calibration with the physical model was carried out using the software PLAXIS 3D Tunnel 2.4. The results showed accurate predictions, especially for the low and middle part of the measured deformations where the numerical analysis proposed a solution that can be considered as safe. Installing FBG sensors on biaxial geogrids was a bold idea that was not easy to implement. However, other possibilities have been successfully tested, such as high-frequency measurements of the response of reinforced soil structure under dynamic loading.

Shaking table test of acceleration response of surrounding rock of the 3D cross tunnel under earthquake

Taking the 3D cross-engineering of Caomeigou No.1 Tunnel and Pandaoling Tunnel as an example, a shaking table test was carried out to study the effect of tunnel spatial position on seismic wave propagation characteristics and acceleration response of surrounding rock under earthquake seismic excitation. Based on the influence of the spatial position of the tunnel, the characteristic form of the surrounding rock between the cross section and non-cross section is divided, and the accelerometer layout scheme is designed. Based on statistical probability, the ratio of peak ground velocity to peak ground acceleration (PGA) was introduced to quantitatively characterize the characteristics of seismic wave propagation spectrum. Furthermore, the SPECTR calculation was used to obtain the regional difference in the seismic wave propagation potential damage potential displacement parameter (P d ). Under the influence of the spatial location of the 3D cross tunnel, the peak acceleration and motion duration of the seismic wave are mainly reflected in the variation of the section along the elevation direction. Low-frequency (≤20 Hz) seismic waves have a greater impact on the tunnel structure, and peak ground velocity/peak ground acceleration ratio has a positive correlation with the peak input energy of ground motion. The ultra-small net-spacing cross tunnel has a spatially distributed coupling deformation effect. The crown of the upper-span tunnel is highly sensitive to earthquakes and becomes a weak link in seismic design. These results help us provide a theoretical basis for the seismic design of the cross-tunnel.

Effects of Karst Cave Shape on the Stability and Minimum Safety Thickness of Tunnel Surrounding Rock

Karst caves are often encountered during karst tunnel excavation, and the shape of the karst cave has an impact on the stability of the tunnel surrounding rock. This paper focused on the effects of karst cave shape on the stability and minimum safety thickness of tunnel surrounding rock. First, the 3D water-filled karst cave and tunnel models were established, and the tunnel excavation simulation under the different height–span ratios of the karst cave was carried out. Second, the stress and displacement fields of the surrounding rock were analyzed, and the change laws of stress and displacement with tunnel excavation were revealed. Third, on the basis of simulation results, the formulas for the minimum safety thickness of surrounding rock resisting water inrush were derived based on the catastrophe theory and strength theory. Finally, the numerical simulation and theoretical formulas were verified by contrastive analysis of the specific engineering project. The results showed that (1) as the height–span ratio of the top karst cave increases, the principal stress of the surrounding rock increases gradually, as well as the Y-displacement of tunnel vault and bottom; (2) the influence of height–span ratios of the top karst cave on the maximum principal stress and displacement of the tunnel vault is the largest; and (3) the formula for the minimum safety thickness of rock resisting water inrush is obtained based on the catastrophe theory. The research results have certain reference significance and engineering application value for the prevention and control of water inrush disasters in karst tunnels and other similar underground engineering construction.