Applied Sciences

Editorial

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4 pages, 164 KiB

Open AccessEditorial

Deep Rock Mass Engineering: Excavation, Monitoring, and Control

by Pengfei Li, Qing Xu and Qian Fang

Appl. Sci. 2022, 12(22), 11721; https://doi.org/10.3390/app122211721 - 18 Nov 2022

Viewed by 1007

Abstract

With the continuing development of the global economy and society, the exploitation of underground space is undergoing an unprecedented prosperity period [...] Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

Research

Jump to: Editorial

13 pages, 53448 KiB

Open AccessArticle

A Novel Continuous-Discontinuous Multi-Field Numerical Model for Rock Blasting

by Yunpeng Li, Chun Feng, Chenxi Ding and Yiming Zhang

Appl. Sci. 2022, 12(21), 11123; https://doi.org/10.3390/app122111123 - 02 Nov 2022

Cited by 2 | Viewed by 1278

Abstract

During blasting, rock failure is caused by blasting wave and explosive gas pressure, as a multi-field coupled process. Most numerical models focus on the effect of blasting wave where the gas pressure is commonly accounted for by empirical relations, ignoring the penetration and [...] Read more.

During blasting, rock failure is caused by blasting wave and explosive gas pressure, as a multi-field coupled process. Most numerical models focus on the effect of blasting wave where the gas pressure is commonly accounted for by empirical relations, ignoring the penetration and permeation of gas flow in cracks. This can underestimate the failure region. In this work, a novel multi-field model is developed in the framework of a continuous-discontinuous element method (CDEM), which is a coupled finite-discrete method with explicit integration strategy. The deformation and cracking of rock mass and the distribution of gas pressure are captured. The proposed method is verified by comparing the results to other results provided in published literature. Especially, by simulating the cases with blocked and unblocked blasting hole, we found that: (i) The fracture degree of the case with blocked blasting hole was 30% higher than that of the unblocked blasting hole. (ii) The radial main cracks in the fracture area are mainly caused by the explosive gas, and the tiny and dense cracks near the hole are induced by the explosion stress wave. (iii) The explosion crushing zone is mainly formed by the action of explosion stress wave, while the crack zone is formed by the combined action of the explosion stress wave and explosive gas. The proposed method provides a useful tool to properly simulate a rock blasting process. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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16 pages, 4528 KiB

Open AccessArticle

Experimental Investigation of Crystal Blocking in Drainage Pipes for Tunnels in the Karst Region

by Chongbang Xu, Yang Chen, Yunxuan Yang, Pengfei Li, Siqing Wang and Lei Li

Appl. Sci. 2022, 12(21), 10928; https://doi.org/10.3390/app122110928 - 28 Oct 2022

Cited by 2 | Viewed by 1519

Abstract

Crystal blockage of tunnel drainage pipes is one of the main causes of problems such as lining cracking and water leakage. The study of the crystal development rule is of great significance for the design of tunnel drainage systems and the long-term safety [...] Read more.

Crystal blockage of tunnel drainage pipes is one of the main causes of problems such as lining cracking and water leakage. The study of the crystal development rule is of great significance for the design of tunnel drainage systems and the long-term safety of tunnel support structures. In this paper, a series of experimental studies on the crystallization development law of drain pipes are conducted. The effects of the connection method of the drain, the diameter of the pipe, the spacing of the circular drain, and the material of the drain on the crystallization development pattern are investigated. The results show that the groundwater environment has a great influence on the crystallization development of the drain pipe. As the drain diameter and the spacing between two adjacent circular drains increased, the time for complete blockage of the drain is prolonged. The rate of crystallization on the drainage pipe can be effectively reduced by changing the material of the drainage pipe from polyamide (PA) to polypropylene (PP). The present study provides a reference for research work related to crystallization blockage in tunnel drainage pipes. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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17 pages, 5795 KiB

Open AccessArticle

Mechanical Behaviors of Existing Large-Diameter Tunnel Induced by Horseshoe-Shaped Undercrossing Twin Tunnels in Gravel

by Jianye Li, Qian Fang, Xiang Liu, Jianming Du, Gan Wang and Jun Wang

Appl. Sci. 2022, 12(14), 7344; https://doi.org/10.3390/app12147344 - 21 Jul 2022

Cited by 4 | Viewed by 1543

Abstract

This article investigates and presents a case study on the Beijing Subway Line 12 excavation beneath the existing Qinghuayuan Tunnel. The composite pre-reinforcement technique was used in conjunction with the shallow tunneling method to control the distortion of the existing large-diameter tunnel. When [...] Read more.

This article investigates and presents a case study on the Beijing Subway Line 12 excavation beneath the existing Qinghuayuan Tunnel. The composite pre-reinforcement technique was used in conjunction with the shallow tunneling method to control the distortion of the existing large-diameter tunnel. When building twin tunnels underneath, this strategy considerably decreased the impact on the existing large-diameter tunnel. To systematically study the mechanical response of the existing large-diameter tunnel, a variety of sensors was embedded in the prefabricated segments just above the new twin tunnels. During the undercrossing twin tunnels procedure, the earth pressure, tunnel crown settlement, opening width of the segment joint, and the circumferential strain of the large-diameter existing tunnel were all measured. The settlement development of the existing large-diameter tunnel was categorized under six stages: (1) sedimentation, (2) heave, (3) second sedimentation, (4) second heave, (5) third sedimentation, and (6) steady state. The joint opening of the existing large-diameter tunnel changed sharply during the new undercrossing twin tunnels. The earth pressure and concrete stress of the linings rapidly increased during the new undercrossing twin tunnels. The majority of the reinforcement and concrete stresses were compressive and far lower than the yield strength, indicating that the tunnel was in a safe working condition. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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16 pages, 5799 KiB

Open AccessArticle

Research on the Stress Characteristics of Initial Tunnel Supports Based on Active Load Adjustment

by Ke Ma, Li-Ping Chen and Qian Fang

Appl. Sci. 2022, 12(14), 7214; https://doi.org/10.3390/app12147214 - 18 Jul 2022

Cited by 4 | Viewed by 1111

Abstract

Initial tunnel support takes on a critical significance in the stability control of surrounding rocks and the core content of tunnel support design. Its stability and safety are essential to the tunnel. The support load was optimized using the active surrounding rock load [...] Read more.

Initial tunnel support takes on a critical significance in the stability control of surrounding rocks and the core content of tunnel support design. Its stability and safety are essential to the tunnel. The support load was optimized using the active surrounding rock load intervention scheme in accordance with the section form and bearing characteristics of the support structure. The optimization scheme of active surrounding rock load was obtained by applying active intervention load to the initial support of the tunnel to minimize the peak moment of the support structure. An active adjustment system for tunnel-surrounding rock loads was developed using the function of hydraulic load transfer and transmission combined with load proportion control. Based on the actual project, the implementation effect of the surrounding rock load active intervention scheme was verified by analyzing the measurement results of the supporting structure in the test section and the comparison section. The results suggest that the application of active intervention load can effectively improve the stress state of the tunnel initial support structure, significantly reduce the tunnel surrounding rock bias pressure and the structural peak bending moment, and increase the stability of the support structure. To control the peak moment of the supporting structure, an active intervention method and its implementation scheme for the stress of the tunnel supporting structure were proposed, which reduces the deficiency in which the conventional supporting structure can only passively bear the deformation pressure of the surrounding rock, effectively improves the stress state of the supporting structure, and can provide a reference for the development of novel tunnel supporting forms. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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17 pages, 10303 KiB

Open AccessArticle

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

by Zhijie Sun, Xuanyu Yang, Shuai Lu, Yang Chen and Pengfei Li

Appl. Sci. 2022, 12(13), 6750; https://doi.org/10.3390/app12136750 - 03 Jul 2022

Cited by 7 | Viewed by 1379

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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22 pages, 14939 KiB

Open AccessArticle

Analysis of Shield Tunnel Ground Deformation Characteristics and Affecting Factors in Water-Rich Soft Stratum: A Case Study on the Section Tunnel of Tianjin Metro Line 6

by Xinyu Li, Dingli Zhang and Yanjuan Hou

Appl. Sci. 2022, 12(12), 6208; https://doi.org/10.3390/app12126208 - 18 Jun 2022

Cited by 8 | Viewed by 1611

Abstract

With the increasing intensity of underground development, the planned metro lines will inevitably pass through water-rich soft stratum. The existing research results show that shield tunneling in water-rich stratum is prone to ground settlement and segment cracking due to the large moisture content [...] Read more.

With the increasing intensity of underground development, the planned metro lines will inevitably pass through water-rich soft stratum. The existing research results show that shield tunneling in water-rich stratum is prone to ground settlement and segment cracking due to the large moisture content and the low soil strength, which will pose risks to the safety of construction. The prediction of ground deformation characteristics and influencing ranges caused by shield tunneling in water-rich soft stratum has been a topical issue among the tunnel research community. Based on the shield tunnel project of Tianjin Metro Line 6, supported by the monitoring data, this paper analyses the ground deformation characteristics caused by shield tunneling in water-rich soft stratum. The results suggest that the surface settlement ranges from −14.20 mm to −28.00 mm in Tianjin’s water-rich soft stratum, which is at an acceptable level of engineering. A refined 3D model addressing fluid–structure interactions is developed to consider the construction process in water-rich soft stratum. Based on this technique, this article focuses on the effect of the support pressure at the excavation surface, the friction between the shield skin and the soil, and synchronous grouting quantity on the ground settlement and structural deformation. The results show that the friction between the shield skin and the soil is the most detrimental to deformation control, whereas the synchronous grouting quantity is the most advantageous to ground and segment deformation control. In practice, timely injection of bentonite slurry reduces friction between the shield skin and the soil, and effective synchronous grouting reduces shield tunneling disruption. This technique can provide calculation support in the optimization of shield tunneling schemes in water-rich soft stratum. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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14 pages, 4533 KiB

Open AccessArticle

Modification of Segment Structure Calculation Theory and Development and Application of Integrated Software for a Shield Tunnel

by Qingfei Huang, Shaopeng Liu, Yonggang Lv, Daxue Ji and Pengfei Li

Appl. Sci. 2022, 12(12), 6043; https://doi.org/10.3390/app12126043 - 14 Jun 2022

Cited by 1 | Viewed by 1260

Abstract

From the aspect of calculation theory, the beam–spring model method and modified routine method of shield tunnel segment structure calculation were improved, and an efficient integrated software system for segment structure calculation of shield tunnel was developed. The beam–spring method is generally calculated [...] Read more.

From the aspect of calculation theory, the beam–spring model method and modified routine method of shield tunnel segment structure calculation were improved, and an efficient integrated software system for segment structure calculation of shield tunnel was developed. The beam–spring method is generally calculated according to the assumption of continuous displacement between beams and joints, and the existing modified routine method assumes that the lateral pressure gradient is constant generally, which does not consider the variation in lateral pressure gradient caused by the difference in the lateral pressure coefficient of soil layers or the water level height, which has a certain deviation from the actual situation. The existing beam–spring method and modified routine method theory were improved, the discontinuous displacement between beams and joints in the beam–spring method was taken into account, and the problem of lateral pressure gradient change in the modified routine method was solved. The calculation software system developed by C# and python programming language was proposed to improve the accuracy and efficiency of segment structure calculation. Based on the actual monitoring data of the internal force of the shield tunnel segment and the adjacent shield tunnel segments under construction in Changsha, China, the segments of the shield tunnel with different cross-section sizes and different hydrogeological conditions are calculated to verify the reliability of the calculation software system. At the same time, combined with the calculation results of the software system and field test data, the stiffness reduction coefficient and equivalent foundation resistance coefficient in the modified routine method were derived to further improve the accuracy of the calculation results, which provided a new idea for the calculation of segment structure of shield tunnel with different diameters under different hydrogeological conditions. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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23 pages, 5872 KiB

Open AccessArticle

Numerical Simulation of Non-Stationary Parameter Creep Large Deformation Mechanism of Deep Soft Rock Tunnel

by Jiancong Xu, Haiyang Wen, Chen Sun, Chengbin Yang and Guorong Rui

Appl. Sci. 2022, 12(11), 5311; https://doi.org/10.3390/app12115311 - 24 May 2022

Cited by 5 | Viewed by 1580

Abstract

The accelerated creep plays an important role in the disasters of soft-rock tunnels under high stress. However, most of previous studies only involved attenuation creep and uniform creep. Large deformation disasters of soft rock occurred during the tunneling process in the Qianzhou–Sanyangchuan Tunnel, [...] Read more.

The accelerated creep plays an important role in the disasters of soft-rock tunnels under high stress. However, most of previous studies only involved attenuation creep and uniform creep. Large deformation disasters of soft rock occurred during the tunneling process in the Qianzhou–Sanyangchuan Tunnel, Gusu Province, China. In the paper, we developed the nonlinear generalized Nishihara rheological model with non-stationary parameter creep (NGNRM) to simulate the accelerated creep behaviors of soft rocks under high stress, and implemented it in ABAQUS, to reveal the mechanism of large deformation of soft rock. We proposed the multi-objective back analysis method of surrounding rock mechanical parameters based on the eXtreme Gradient Boosting and the non-dominated sorting genetic algorithm-II. In addition, the orthogonal test design method was used to determine the main parameters affecting the displacement of the tunnel. Using the proposed method, we can evaluate the large deformation mechanism of deep soft rock tunnels, and scientifically determine when to reinforce to prevent a large deformation disaster of the tunnel. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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20 pages, 9723 KiB

Open AccessArticle

Monitoring and Analysis of Deformation Refinement Characteristics of a Loess Tunnel Based on 3D Laser Scanning Technology

by Yimin Wu, Zhuangzhuang Zhou, Shuai Shao, Zhizhong Zhao, Kaixun Hu and Sijie Wang

Appl. Sci. 2022, 12(10), 5136; https://doi.org/10.3390/app12105136 - 19 May 2022

Cited by 5 | Viewed by 1279

Abstract

Loess tunnels often undergo large-scale deformation with complex spatial and temporal distribution. Mastering the characteristics of spatial and temporal deformation is conducive to precise policy implementation and the control of large deformation of the tunnel. In this study, relying on the Yulinzi Tunnel [...] Read more.

Loess tunnels often undergo large-scale deformation with complex spatial and temporal distribution. Mastering the characteristics of spatial and temporal deformation is conducive to precise policy implementation and the control of large deformation of the tunnel. In this study, relying on the Yulinzi Tunnel in Gansu Province, China, based on 3D laser scanning technology, the tunnel was monitored for a short period of 24 h and a long period of 36 days. The refined characteristics of the temporal and spatial deformation of the representative points of the interrupted surface, the tunnel face, and the excavation mileage during the excavation process of the three-bench and seven-step method of the tunnel were analyzed. The results show that the tunnel’s arch has large deformation, and there is twisting deformation. The distribution of the overall deformation of the tunnel is related to the excavation sequence, showing a stepped deformation law. With the construction of the following excavation process, the deformation rate of the tunnel always indicates the characteristics of significant in the early stage and small in the later stage, and the overall deformation changes with time in accordance with the distribution law of the exponential function. The research results provide a reference for predicting the deformation development trend of loess tunnels and providing reasonable deformation control methods. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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21 pages, 3775 KiB

Open AccessArticle

Analytical Prediction of Strip Foundation Building Response to Shallow Tunneling Considering the Tunneling Process

by Lin Yu, Dingli Zhang, Qian Fang, Yujie Li, Gang Wang and Liqiang Cao

Appl. Sci. 2022, 12(9), 4656; https://doi.org/10.3390/app12094656 - 06 May 2022

Cited by 2 | Viewed by 1267

Abstract

This paper presents an analytical method to predict the response of a strip foundation building to shallow tunneling based on the two-stage method. The existing building is simplified as a Euler–Bernoulli beam resting on the Pasternak model. The tunneling process and different relative [...] Read more.

This paper presents an analytical method to predict the response of a strip foundation building to shallow tunneling based on the two-stage method. The existing building is simplified as a Euler–Bernoulli beam resting on the Pasternak model. The tunneling process and different relative positions between the tunnel and the existing building can be considered in the proposed method. The accuracy of the proposed method is verified through comparisons with results from the finite element and finite difference methods. The results indicate that the differential settlement of the building reaches a maximum and the rotation angles are symmetric with respect to the building centerline when the tunnel face arrives at the middle of the building. The maximum bending moments occur at the middle of the building, while the maximum shear forces occur at about one-fifth and four-fifths of the building length when the tunnel face is located at the two ends of the building. According to the parametric analysis, the alignment angle, elastic modulus and Poisson’s ratio of the soil, bending stiffness, and gap parameter greatly affect the building response. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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18 pages, 7097 KiB

Open AccessArticle

A Semi-Analytical Model and Parameter Analysis of a Collaborative Drainage Scheme for a Deeply Buried Tunnel and Parallel Adit in Water-Rich Ground

by Xiongwen Luo, Yanyong Xiang and Chenyun Yu

Appl. Sci. 2022, 12(8), 3759; https://doi.org/10.3390/app12083759 - 08 Apr 2022

Cited by 3 | Viewed by 1430

Abstract

For a railway or highway tunnel under high water pressure during operation, various factors such as the design of the drainage system, material aging, and pipeline blockage must be considered for the tunnels to work with the parallel adit to drain and control [...] Read more.

For a railway or highway tunnel under high water pressure during operation, various factors such as the design of the drainage system, material aging, and pipeline blockage must be considered for the tunnels to work with the parallel adit to drain and control the external water pressure on the tunnel lining. A simplified steady-state seepage model in a semi-infinite multi-connected domain for the tunnel and parallel adit was established and was solved iteratively using the complex variable method and the Schwartz alternating method. After verifying the numerical simulation, parametric analysis, orthogonal tests, and multivariate nonlinear regression were also carried out. Results show that the simplified theoretical model and its semi-analytical algorithm have a fast convergence speed, and the obtained regression formula is simple, which is suitable for calculation and parameter analysis. A scheme that primarily relies on the parallel adit for drainage would make the external water pressure of the lining facing the parallel adit side less than that of the opposite side. Therefore, to reduce pressure uniformly and meet the requirements of surrounding rock stability, the horizontal net distance between the parallel adit and the tunnel should be no less than the tunnel diameter. Drainage volume of the parallel adit is linearly negatively correlated with tunnel water pressure on the lining and has the most significant effect on pressure reduction. The influence of the vertical distance between the parallel adit and the tunnel on water pressure is small. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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17 pages, 5096 KiB

Open AccessArticle

Effects of New Tunnelling on a Buried Pipeline with Joints and Its Detachment

by Ye Dong, Xiang Liu, Rui Zhang and Chengyong Yang

Appl. Sci. 2022, 12(7), 3342; https://doi.org/10.3390/app12073342 - 25 Mar 2022

Cited by 3 | Viewed by 1445

Abstract

The interactions between the buried pipeline and tunnelling-induced ground movement are studied in this paper, in which the jointed pipeline, Pasternak foundation, and the detachment are considered. A mathematical model using the pulse function is provided to simplify the jointed pipeline to a [...] Read more.

The interactions between the buried pipeline and tunnelling-induced ground movement are studied in this paper, in which the jointed pipeline, Pasternak foundation, and the detachment are considered. A mathematical model using the pulse function is provided to simplify the jointed pipeline to a continuous pipeline with additional local rotations. The determination of detachment is used by the usual iteration method. The finite difference method is utilized to obtain the numerical results. The results calculated by our proposed method agree with the experimental data of centrifuge tests and are close to those obtained by the other methods. The deflection and bending moment of the jointed pipeline can be predicted reasonably, as well as its detachment location. Parametric analyses about the main influencing factors are carried out. The stiffness reduction factor is significant to the discontinuous behavior of the jointed pipeline. During the parametric analyses, the detachment beneath the jointed pipeline sometimes happens and sometimes does not. The responses of the jointed pipeline and its detachment require priority attention. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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19 pages, 4412 KiB

Open AccessArticle

Structural Stress Characteristics and Joint Deformation of Shield Tunnels Crossing Active Faults

by Hanyuan Li, Xinggao Li, Yi Yang, Yang Liu and Mingzhe Ma

Appl. Sci. 2022, 12(7), 3229; https://doi.org/10.3390/app12073229 - 22 Mar 2022

Cited by 11 | Viewed by 1937

Abstract

Fault dislocation severely threatens the safety of a tunnel structure. Formerly, researchers mainly engaged in the mechanical response of mountain tunnels crossing the fault fracture zone. In contrast, few studies have focused on the structural stress characteristics and joint deformation of the cross-fault [...] Read more.

Fault dislocation severely threatens the safety of a tunnel structure. Formerly, researchers mainly engaged in the mechanical response of mountain tunnels crossing the fault fracture zone. In contrast, few studies have focused on the structural stress characteristics and joint deformation of the cross-fault shield tunnels. There is an apparent difference between segmental tunnels and mountain tunnels with respect to mechanical properties. In the current study, a three-dimensional numerical model of cross-fault segmental tunnels is established based on the theory of concrete plastic damage constitutive relations using the finite element program ABAQUS. The numerical calculation results are compared with the model test results for validation. Subsequently, the relevant factors affecting the mechanical response of the shield tunnel crossing the active fault are analyzed. The results illustrate that when normal fault dislocation occurs, the shield tunnel structure is initially damaged appearing in the circumferential joints, which is prone to large tension deformation. Otherwise, when reverse faulting occurs by the same displacement, the shield tunnel structure is initially damaged at the arch haunch of the segments, and the deformation of the longitudinal joints is relatively slight. Under the same fault displacement, the bearing capacity of the segmental lining subjected to the reverse fault dislocation is more significant than that of the normal fault dislocation. Both the soil elastic modulus and the vertical distance between the top of the fault and the tunnel exert a considerable impact on the structural damage of the segmental tunnels, bolt stress, and joint deformation. The fault dip angle does not affect the mechanical characteristics of the shield tunnel structure when subjected to normal fault displacement. In reverse faulting cases, with the increase of the fault dip angle, the tunnel structural failure mode transforms from the transverse compression failure of the segments to the shear failure of the circumferential joints. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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19 pages, 3607 KiB

Open AccessArticle

A New Numerical Finite Strain Procedure for a Circular Tunnel Excavated in Strain-Softening Rock Masses and Its Engineering Application

by Wenbo Chen, Dingli Zhang, Qian Fang, Xuanhao Chen and Tong Xu

Appl. Sci. 2022, 12(5), 2706; https://doi.org/10.3390/app12052706 - 05 Mar 2022

Cited by 5 | Viewed by 1768

Abstract

The small strain theory underestimates the self-bearing capacity of rock masses, especially for a soft rock tunnel under high geostress. To perform an efficient and accurate calculation and provide a reference for the stiffness design of a tunnel, the finite strain solution for [...] Read more.

The small strain theory underestimates the self-bearing capacity of rock masses, especially for a soft rock tunnel under high geostress. To perform an efficient and accurate calculation and provide a reference for the stiffness design of a tunnel, the finite strain solution for a circular tunnel in Mohr–Coulomb strain-softening rock masses with a non-associated flow rule was derived as three sets of differential equations under the Lagrangian coordinate, which are in the residue region, the softening region, and the elastic region, respectively. Based on the bisection method, an iteration procedure for solving the finite strain solution was proposed to approximate the boundary condition at infinity, the values of two adjacent boundaries, and the initial values on the excavation boundary. This numerical procedure was verified by comparing with self-similar solutions, recursive solutions, and FLAC simulation results. In the calculation example, the relative error on boundaries can be decreased to less than 10⁻⁸ after only 10 times iteration and the time for each calculation is less than 15 s. Applying this procedure on the sensibility analysis and stiffness reliability design for the Zhongyi tunnel, a support stiffness of 4.3 MPa/m is recommended to guarantee a tunnel displacement lower than 0.5 m. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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16 pages, 2182 KiB

Open AccessArticle

Algorithm for an Effective Ratio of the Transverse Bending Rigidity Based on the Segment Joint Bending Stiffness

by Dawei Huang, Hao Jiang, Wenjun Luo, Hao Xiong, Baizan Tang and Jinhui Xu

Appl. Sci. 2022, 12(4), 1901; https://doi.org/10.3390/app12041901 - 11 Feb 2022

Cited by 7 | Viewed by 1409

Abstract

An algorithm for calculating the effective ratio of the transverse bending rigidity is established based on the segment longitudinal joint bending stiffness. With the knowledge of this effective ratio, the bending rigidity of a modified uniform rigidity ring is fully defined. To verify [...] Read more.

An algorithm for calculating the effective ratio of the transverse bending rigidity is established based on the segment longitudinal joint bending stiffness. With the knowledge of this effective ratio, the bending rigidity of a modified uniform rigidity ring is fully defined. To verify this developed algorithm, the effective ratios and convergence deformations of the modified uniform rigidity rings obtained with different methods are compared. Moreover, the responses of the modified uniform rigidity ring model under loading obtained from this algorithm are compared to those obtained with the existing generally accepted beam-spring model. The results show that although the bending moments obtained from these two models are different, the axial forces, horizontal convergent deformations, and vertical convergent deformations are quite consistent with each other. The modified uniform rigidity ring model built on the developed effective ratio algorithm is applicable for the analysis of the tunnel convergence deformation and the interaction between the tunnel structure and the ground during operation. This modified uniform rigidity ring model is simpler and easier to use than the beam-spring model; thus, the significance of the developed algorithm for the effective ratio of the transverse bending rigidity is demonstrated. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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15 pages, 4361 KiB

Open AccessFeature PaperArticle

Estimating Volume Loss for Shield-Driven Tunnels Based on the Principle of Minimum Total Potential Energy

by Gan Wang, Qian Fang, Jianming Du, Xiaoxu Yang and Jun Wang

Appl. Sci. 2022, 12(4), 1794; https://doi.org/10.3390/app12041794 - 09 Feb 2022

Cited by 4 | Viewed by 2592

Abstract

Volume loss is an important method to estimate ground movement during tunnelling. However, volume loss is usually estimated by empirical methods, especially for volume loss at the tunnel face, which is a three-dimensional problem. Based on the principle of minimum total potential energy, [...] Read more.

Volume loss is an important method to estimate ground movement during tunnelling. However, volume loss is usually estimated by empirical methods, especially for volume loss at the tunnel face, which is a three-dimensional problem. Based on the principle of minimum total potential energy, we proposed a semi-analytical method to predict the volume loss at the tunnel face and ground surface. The proposed method provides a more direct way of estimating volume loss at the tunnel face from an energy point of view. Moreover, a new deformation mechanism was designed to describe the ground movement before the tunnel face. Based on the proposed method, we investigated the influence of the support pressure, tunnel diameter, and tunnel depth on the volume loss at the tunnel face, and other parameters related to surface subsidence. The volume loss at the tunnel face decreased with the increase in the support pressure ratio and the slurry weight. The volume loss at ground surface was generally smaller than the volume loss at the tunnel face due to the soil compression during ground movement. The bigger the tunnel diameter, the bigger the volume loss at the tunnel face. However, the volume loss at ground surface may not increase with the increase in tunnel depth, because of the soil arching effect. Moreover, the deeper the tunnel, the more obvious the influence of the support pressure ratio on volume loss. Similarly, the bigger the tunnel diameter, the more obvious the influence of the slurry weight on the volume loss. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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15 pages, 8187 KiB

Open AccessArticle

Effect of Excavation Blasting in the Arch Cover Method on Adjacent Existing Pipelines in a Subway Station

by Xiang Liu, Annan Jiang, Xinping Guo and Lu Hai

Appl. Sci. 2022, 12(3), 1529; https://doi.org/10.3390/app12031529 - 31 Jan 2022

Cited by 6 | Viewed by 1856

Abstract

The dynamic responses of existing pipelines are of great significance to be studied in blasting excavation in the arch cover method. In this paper, the Shi Kui Subway Station Line 5 in Dalian, China, is selected as a case study. A 3D numerical [...] Read more.

The dynamic responses of existing pipelines are of great significance to be studied in blasting excavation in the arch cover method. In this paper, the Shi Kui Subway Station Line 5 in Dalian, China, is selected as a case study. A 3D numerical simulation model is established to analyze the dynamics characteristics of the existing pipelines subjected to blasting vibration, with a triangular pattern describing the blast hole pressure. The numerical simulation is verified by comparing the existing pipelines’ PPVs of the numerical model and field monitored points. Then, the dynamic responses of the pilot tunnels, existing pipelines, and secondary lining are discussed. The effects of the later pilot tunnel on the earlier pilot tunnel are remarkable when the relative distance between them is small. Extensive blasting areas and many charges will result in large peak velocities of the existing pipelines in a short time, as well as a decreased distance from the pilot tunnels. However, the hollow effect can change these dynamic characteristics. The implementation of a secondary lining can reduce the existing pipelines’ dynamic responses when the lower rock is blasted. The most adverse position of the secondary lining is the arch foot rather than the arch crown and arch waist; thus, blasting should be carried out at a suitable age for the concrete to ensure the safety of the structures and pipelines. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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11 pages, 2446 KiB

Open AccessArticle

Analysis of Characteristics of Roof Fall Collapse of Coal Mine in Qinghai Province, China

by Ya-Jie Wang, Lin-Shuang Zhao and Ye-Shuang Xu

Appl. Sci. 2022, 12(3), 1184; https://doi.org/10.3390/app12031184 - 24 Jan 2022

Cited by 7 | Viewed by 2575

Abstract

This paper presents the roof fall collapse of a coal mine that occurred, causing 20 deaths and 1 injury, in Qinghai Province, China, on 14 August 2021. After the primary investigation of this incident and a brief description of the rescue action undertaken, [...] Read more.

This paper presents the roof fall collapse of a coal mine that occurred, causing 20 deaths and 1 injury, in Qinghai Province, China, on 14 August 2021. After the primary investigation of this incident and a brief description of the rescue action undertaken, this report discussed the possible reasons behind this disaster. The fissure water and damaged rock mass are the dominant triggering factors of this incident. Little concern for risk assessment and monitoring systems is one of the main man-made mistakes. Consequently, the reflections and suggestions are put forward to reduce or prevent the occurrence of roof fall incidents in coal mines. The noteworthy actions that are necessary in coal mine projects are conducting risk assessments based on geological condition and building proper support systems for coal mines considering he situation in situ. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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13 pages, 2053 KiB

Open AccessArticle

Analysis of Crack Formation and Growth in Tunnel Linings Using Double-K Fracture Criterion

by Chengjun Huang, Xinrui Li and Ming Wen

Appl. Sci. 2022, 12(3), 1064; https://doi.org/10.3390/app12031064 - 20 Jan 2022

Cited by 3 | Viewed by 2102

Abstract

Empirical criteria and fracture/damage mechanics are used to evaluate the safety of lining cracks in the conventional methods. However, the former lacks a scientific basis, and the latter requires complicated mechanical calculations. To overcome the above shortcomings, this paper proposes a new method [...] Read more.

Empirical criteria and fracture/damage mechanics are used to evaluate the safety of lining cracks in the conventional methods. However, the former lacks a scientific basis, and the latter requires complicated mechanical calculations. To overcome the above shortcomings, this paper proposes a new method to perform crack analysis of plain concrete linings, based on the double-K fracture criterion. The proposed method uses two crack width indices, i.e., initiation and unstable fracture widths, to divide the fracture process of lining into three stages: initiation stage, stable propagation stage, and instability propagation stage. These two crack width indices are calculated by the equivalent transformation of fracture toughness. Using the proposed criterion, the safety state of the concrete lining can be determined by comparing the field measurement width and crack width indices. A specific code based on the extended finite element method (XFEM) is developed to simulate the fracture process of concrete lining. Several numerical experiments are carried out to evaluate the proposed fracture criterion. The results show that the two fracture indices of the proposed criterion can accurately identify two demarcation points of the three stages of the lining fracture process, including the nonlinear starting point and the unstable fracture point of the load–displacement curve. Compared with conventional methods, the proposed method uses the geometric parameter to estimate the mechanical state of cracks, so the complicated mechanical calculation can be avoided. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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13 pages, 12660 KiB

Open AccessArticle

Criteria for Cutting Head Clogging Occurrence during Slurry Shield Tunneling

by Xinggao Li, Yi Yang, Xingchun Li and Hongzhi Liu

Appl. Sci. 2022, 12(3), 1001; https://doi.org/10.3390/app12031001 - 19 Jan 2022

Cited by 11 | Viewed by 1689

Abstract

Cutting head clogging is more frequently encountered as more tunnels are being excavated by slurry shield machines. So establishing criteria for cutting head clogging occurrence based on the machine driving parameters is of great engineering significance. Three construction cases of the Beijing south-to-north [...] Read more.

Cutting head clogging is more frequently encountered as more tunnels are being excavated by slurry shield machines. So establishing criteria for cutting head clogging occurrence based on the machine driving parameters is of great engineering significance. Three construction cases of the Beijing south-to-north water diversion auxiliary project, the Jinan Huanghe River Crossing tunnel construction, and the Wuhan Metro Line 8 Yangtze River Crossing tunnel construction, are introduced. Development of the main driving parameters in the construction cases, including the total thrust, the cutting head torque, the advance rate, and the cutting head rotation speed of the tunneling machines before, during, and after the cutting head clogging, are presented and analyzed. The fact is that the total thrust and the cutting head torque of tunneling machines will increase, or will not, once the cutting head clogging occurs. It is recommended to take two combined parameters of total thrust/penetration depth and cutting head torque/penetration depth into account to judge whether the cutting head clogging will occur or not. The maximum increases of the composite parameters by 2–6 times are found in the construction cases. But for the minimum increase, a 30–50% increase of the composite parameter should be noted. The findings can be of great help for similar projects. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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20 pages, 8755 KiB

Open AccessArticle

Spatiotemporal Deformation of Existing Pipeline Due to New Shield Tunnelling Parallel Beneath Considering Construction Process

by Xiang Liu, Annan Jiang, Qian Fang, Yousheng Wan, Jianye Li and Xinping Guo

Appl. Sci. 2022, 12(1), 500; https://doi.org/10.3390/app12010500 - 05 Jan 2022

Cited by 8 | Viewed by 1557

Abstract

In this paper, we study the effects of the shield tunnel construction on the deformation of an existing pipeline parallel to and above the new shield tunnel. We propose an analytical solution to predict the spatiotemporal deformation of the existing pipeline and consider [...] Read more.

In this paper, we study the effects of the shield tunnel construction on the deformation of an existing pipeline parallel to and above the new shield tunnel. We propose an analytical solution to predict the spatiotemporal deformation of the existing pipeline and consider different force patterns of the shield tunnelling, i.e., ground volume loss, support pressure, frictional force, and torsional force. The proposed method is validated by the monitoring data of Subway Line 3 of Nanchang and provides a reasonable estimation of the pipeline’s deformation. The parametric analyses are performed to study the influences on the pipeline’s deformation. The main advantage of our paper is that the spatiotemporal characteristics of the existing pipeline’s deformation are analysed, providing longitudinal deformation curve (LDC), deformation development curve (DDC), and grouting reinforcement curve (GRC). Compared with the perpendicular undercrossing project, both LDC and DDC have the same profiles and maximum values and move forward as a whole with the shield tunnel advance. Thus, the spatiotemporal deformation of the overall pipeline can be extrapolated from the deformation of two known points on the pipeline. The spatiotemporal characteristic curves combined with LDC, DDC, and GRC can suggest feasible, effective, and economical construction and grouting schemes to control the pipeline’s deformation after the deformation control standards have been determined. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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20 pages, 10300 KiB

Open AccessArticle

Influences of High-Speed Train Speed on Tunnel Aerodynamic Pressures

by Jianming Du, Qian Fang, Jun Wang and Gan Wang

Appl. Sci. 2022, 12(1), 303; https://doi.org/10.3390/app12010303 - 29 Dec 2021

Cited by 11 | Viewed by 2453

Abstract

To comprehensively investigate the characteristics of aerodynamic pressures on a tunnel caused by the whole tunnel passage of a high-speed train at different speeds, we conduct a series of three-dimensional numerical simulations. Based on the field test results obtained by other researchers, the [...] Read more.

To comprehensively investigate the characteristics of aerodynamic pressures on a tunnel caused by the whole tunnel passage of a high-speed train at different speeds, we conduct a series of three-dimensional numerical simulations. Based on the field test results obtained by other researchers, the input parameters of our numerical simulation are determined. The process of a high-speed train travelling through a railway tunnel is divided into three stages according to the spatial relationship between the train and tunnel. Stage I: before train nose enters the entrance; Stage II: while the train body runs inside the tunnel; Stage III: after the train tail leaves the exit. The influences of high-speed train speed on the tunnel aerodynamic pressures of these three stages are systematically investigated. The results show that the maximum peak pressure value decreases with increasing distance from the entrance and increases with increasing train speed in Stage I. There is an approximately linear relationship between the three types of maximum peak pressure (positive peak, negative peak, and peak-to-peak pressures) and the power of the train speed in Stage II. These three types of maximum peak pressure values of the points near tunnel portals increase with increasing train speed in Stage III. Moreover, these three types of maximum peak pressure in the tunnel’s middle section at different train speeds are more complex than those near the tunnel portals, and there is one or more turning points due to the superimposed effects of different pressure waves. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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24 pages, 8283 KiB

Open AccessArticle

Investigation of Deep Shaft-Surrounding Rock Support Technology Based on a Post-Peak Strain-Softening Model of Rock Mass

by Jianjun Zhang, Yang Wang, Baicong Yao, Dongxu Chen, Chuang Sun and Baoxin Jia

Appl. Sci. 2022, 12(1), 253; https://doi.org/10.3390/app12010253 - 28 Dec 2021

Cited by 2 | Viewed by 1797

Abstract

To control the large deformation that occurs in deep shaft-surrounding rock, the post-peak strain-softening characteristics of deep jointed rock mass are discussed in detail. An equivalent post-peak strain-softening model of jointed rock mass is established based on continuum theory and the geological strength [...] Read more.

To control the large deformation that occurs in deep shaft-surrounding rock, the post-peak strain-softening characteristics of deep jointed rock mass are discussed in detail. An equivalent post-peak strain-softening model of jointed rock mass is established based on continuum theory and the geological strength index surrounding rock grading system, and numerical simulations are performed using FLAC^3D software. The convergence-constraint method is used to analyze the rock support structure interaction mechanism. A composiste support technique is proposed in combination with actual field breakage conditions. During the initial support stage, high-strength anchors are used to release the rock stress, and high-stiffness secondary support is provided by well rings and poured concrete. This support technology is applied in the accessory well of a coal mine in Niaoshan, Heilongjiang, China. The stability of the surrounding rock support structure is calculated and analyzed by comparing the ideal elastic-plastic model and equivalent jointed rock mass strain-softening model. The results show that a support structure designed based on the ideal elastic-plastic model cannot meet the stability requirements of the surrounding rock and that radial deformation of the surrounding rock reaches 300 mm. The support structure designed based on the equivalent joint strain-softening model has a convergence rate of surrounding rock deformation of less than 1 mm/d after 35 days of application. The surrounding rock deformation is finally controlled at 140 mm, indicating successful application of the support technology. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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23 pages, 9359 KiB

Open AccessArticle

Effect Mechanism of Connection Joints in Fabricated Station Structures

by Huafei He and Zhaoping Li

Appl. Sci. 2021, 11(24), 11927; https://doi.org/10.3390/app112411927 - 15 Dec 2021

Cited by 6 | Viewed by 1356

Abstract

The seismic response of a fabricated subway station is a complex structural connection problem that depends on the mechanical properties of the joints. In order to obtain the optimal joint distribution of a fabricated station structure under earthquake action, three finite element models [...] Read more.

The seismic response of a fabricated subway station is a complex structural connection problem that depends on the mechanical properties of the joints. In order to obtain the optimal joint distribution of a fabricated station structure under earthquake action, three finite element models of a single ring structure of fabricated subway stations assembled with seven, five, and four prefabricated components were proposed. Seismic wave characteristics, peak acceleration, and coupled horizontal and vertical seismic components were considered to study the seismic response of the fabricated subway station structure with different forms of the joint distribution. The dynamic time history method was used to analyze the seismic response in three aspects: structure plastic strain, interlayer relative deformation, and internal force. The damage indexes and residual strength indexes of the joints were offered based on the concrete damage index to evaluate the joints’ damage degree. The results showed that the joints of the vault or bottom plate had little influence on the seismic response of the fabricated station structure. The sidewall joints had the obvious seismic response and the most severe damage under horizontal ground motion or coupled ground motion, which were the weak joints of the fabricated station structure. The existence of vertical ground motion aggravated the damage degree of sidewall joints, making the damage occurrence time of sidewall joints earlier and the damage end time extended. On the premise of meeting the mechanical load and site requirements, an assembly scheme with fewer prefabricated components can be selected. Full article

(This article belongs to the Special Issue Deep Rock Mass Engineering: Excavation, Monitoring, and Control)

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