Shield TBM Research Articles

Development of Grouting Quality Evaluation System for a Shield TBM Tunnel Using the Impact-Echo Method

Development of Grouting Quality Evaluation System for a Shield TBM Tunnel Using the Impact-Echo Method

Experimental study on the influences of cutter geometry and material on scraper wear during shield TBM tunnelling in abrasive sandy ground

When shield TBM tunnelling in abrasive sandy ground, the rational design of cutter parameters is critical to reduce tool wear and improve tunnelling efficiency. However, the influence mechanism of cutter parameters on scraper wear remains unclear due to the lack of a reliable test method. Geometry and material optimisation are often based on subjective experience, which is unfavourable for improving scraper geological adaptability. In the present study, the newly developed WHU-SAT soil abrasion test was used to evaluate the variation in scraper wear with cutter geometry, material and hardness. The influence mechanism of cutter parameters on scraper wear has been revealed according to the scratch characteristics of the scraper surface. Cutter geometry and material parameters have been optimised to reduce scraper wear. The results indicate that the variation in scraper wear with cutter geometry is related to the cutting resistance, frictional resistance and stress distribution. An appropriate increase in the front angle (or back angle) reduces the cutting resistance (or frictional resistance), while an excessive increase in the front angle (or back angle) reduces the edge angle and causes stress concentration. The optimal front angle, back angle and edge angle for quartz sand samples are α = 25°, β = 10° and γ = 55°, respectively. The wear resistance of the modelled scrapers made of different metal materials is related to the chemical elements and microstructure. The wear resistances of the modelled scrapers made of 45#, 06Cr19Ni10, 42CrMo4 and 40CrNiMoA are 0.569, 0.661, 0.691 and 0.728 times those made of WC-Co, respectively. When the alloy hardness is less than 47 HRC (or greater than 58 HRC), scraper wear decreases slowly with increasing alloy hardness as the scratch depth of the particle asperity on the metal surface stabilizes at a high (or low) level. However, when the alloy hardness is between 47 HRC and 58 HRC, scraper wear decreases rapidly with increasing alloy hardness as the scratch depth transitions from high to low levels. The sensitive hardness interval and recommended hardness interval for quartz sand are [47, 58] and [58, 62], respectively. The present study provides a reference for optimising scraper parameters and improving cutterhead adaptability in abrasive sandy ground tunnelling.

Influence of Pea-Gravel Layer on Segment Ring Support Performance in Shield TBM Tunnels: A Discrete-Continuous Coupling Simulation and Model Test

Influence of Pea-Gravel Layer on Segment Ring Support Performance in Shield TBM Tunnels: A Discrete-Continuous Coupling Simulation and Model Test

Construction practice of water conveyance tunnel among complex geotechnical conditions: a case study

The construction practice of water conveyance tunnels often encounters various complex geotechnical engineering conditions, which bring huge challenges to the design and construction of water conveyance tunnels. Based on the theory of rock elastic–plastic mechanics and finite element analysis technology, this article carried out investigations of engineering geological features, geological formations and hydrological conditions establishes a calculation model for the 3# water conveyance tunnel of the Fenhe River Diversion Project, and analyzes the variation law of surrounding rock stress and displacement during TBM excavation of the tunnel. The results indicate that the dominant direction of the rock mass principal stress measured by the hydraulic fracturing method is NE84°, and the maximum horizontal principal stress, minimum horizontal principal stress, and vertical stress decrease sequentially, analyzing the characteristics of shield TBM construction technology, it is applied to the construction of water transfer tunnels. The numerical simulation of TBM construction using FLAC3D software shows that as the excavation surface advances, the subsidence value of the tunnel roof first slowly increases, then rapidly increases, and then tends to stabilize. The horizontal displacement of the surrounding rock is increasing. The maximum principal stress of the surrounding rock gradually increases. The final surrounding rock stress is 35 MPa. The TBM shield machine with mud water balance driven by indirectly controlled frequency conversion motor is selected for TBM construction of the tunnel. The study offers statistical information to support tunneling technology for water conveyance in the geotechnical engineering practice.

Tunnelling with Full-Face Shielded Machines: A 3D Numerical Analysis of an Earth Pressure Balance (EPB) Excavation Sequence Using the Finite Element Method (FEM)

Urban tunnelling can be highly challenging, especially in areas where limited ground settlements and environmental disturbance is required. Mechanised tunnelling is usually preferred in such ground environments, specifically Slurry or EPBM (Earth Pressure Balance Machine), depending on the ground properties. Being able to predict the anticipated tunnel behaviour at the preliminary stages of the project can be very beneficial in optimising not only the design, but also control the construction activities and completion times. In practice, the short-term excavation response and support performance focus primarily on design, since most site characterisation inputs are focused on material properties gained from short-term testing. Although the analysis of tunnelling is a three-dimensional (3D) problem, conventional approaches and design methods employed during the design and construction of underground openings are often based on the ground’s static response in two dimensions (2D). In this paper, an initial 2D model is generated in PLAXIS2D and RS2 (Rocscience) to test advanced constitutive models and compare transverse settlement profiles; subsequently, a complete 3D FEM numerical model in RS3 (Rocscience) was used to simulate an Earth Pressure Balance (EPB) excavation sequence. The 3D numerical model simulates the relevant EPB components such as face pressure, TBM shield, backfilling of the tail void (time-dependent hardening of the grout) and gradual segmental lining erections in the longitudinal direction. The presented numerical approach can be used by tunnel designers and engineers to predict the soil response in EPBM tunnelling.

Study on Tunnelling Performance of Dual-Mode Shield TBM by Cutterhead Working Performance and Tunnelling Difference Comparison: A Case in Shenzhen Metro Line 12

Study on Tunnelling Performance of Dual-Mode Shield TBM by Cutterhead Working Performance and Tunnelling Difference Comparison: A Case in Shenzhen Metro Line 12

A new evaluation method to quantify the wear failure of irregular cutting tool during shield TBM tunneling in abrasive sandy ground

When shield TBM tunneling in abrasive sandy ground, excessive cutting tool wear resulting from untimely and inaccurate failure evaluation is prone to damage cutterhead structure and delay tunneling progress. Hence it is critical important for fast and accurate evaluation of tool wear failure. At present, caliper measurement method is used to qualify cutting tool wear in abrasive ground tunneling. The height reduction of cutter edge is considered as a common parameter to evaluate whether cutting tool is invalid. When it comes to irregular cutting tool, they will be unsuitable due to the complex surface topography. Especially when abrasive sand remains between the cutterhead and excavation face, severe secondary wear will occur on cutter body instead of cutter edge. There is still a lack of comprehensive methods and parameters for evaluating the wear failure of cutting tools. In the present study, the handheld 3D laser scanner has been applied to obtain the point cloud data of irregular cutting tool. The point cloud data has been imported into the Geomagic Control software for model reconstruction. Then, surface overlapped methodology has been utilized for the comparison of cutting tool models before and after wear to obtain the 3D wear nephogram. Cutter volume wear ratio (CVWR) and cutter height wear ratio (CHWR) have been proposed to quantity the wear failure of cutter edge and cutter body. A case study of ripper tooth and replaceable scraper at Sutong GIL Yangtze River Crossing Cable Tunnel has been conducted to set the threshold value of wear failure. The results indicate that the CVWR and CHWR are functional to identify the wear failure of irregular cutting tools. Compared with traditional caliper measurement method, 3D quantitative method allows a more rational and accurate evaluation of heterogeneous cutter edge wear and eccentric cutter body wear.

New soil abrasion testing method for evaluating the influence of geological parameters of abrasive sandy ground on scraper wear in TBM tunneling

When shield TBM tunneling in abrasive sandy ground, scrapers are loaded with heavy forces resulting from the extrusion and friction processes of sand particles. Scraper wear reflected as displacement or desquamation is related to soil parameters. Due to the lack of reliable test methods, experimental studies on the influence of soil parameters on scraper wear are limited. In the present study, existing soil abrasion testers have been reviewed to discuss the advantages and deficiencies. An improved WHU-SAT soil abrasion tester has been developed to study the influence mechanism of soil parameters on scraper wear. Experimental studies have been conducted to evaluate the variation of scraper wear with quartz content, particle size, particle shape and water content. Two soil abrasion tests have been performed for each case. Scraper wear has been considered to be the average value. The results indicate that scraper wear increases with the increase of quartz content and the growth rate increases. It is related to the particle crushing and adhesion effect of limestone sand. As the average particle size increases, the extrusion and friction between the modeled scraper and the sand particles increases first and then decreases. Thus, scraper wear increases first and then decreases with the increase of average particle size. The trend is generally comparable to the corresponding changes in scraper wear with water content. As quartz balls collide with sand particles and destroy the microscopic friction system composed of scrapers and asperities, scraper wear decreases as the increase of roundness and the falling rate decreases. Optimized solutions such as soil abrasivity evaluation, tunnel alignment optimization and soil discharge improvement have been proposed to alleviate the influence of soil parameters on scraper wear. The present study promotes the rational estimation of sand abrasivity and scraper consumption during the feasibility study of abrasive sandy gournd tunneling using shield TBM.

An Operating Model for an EPB Shield TBM Simulator by the Correlation Analysis of Operational Actions and Mechanical Responses

This study reports on the development of an operating model for an EPB Shield TBM simulator by the correlation between operating parameters. First, four main operating parameters required for excavation are analyzed, then multiple regression analysis estimates their requirements depending on the ground conditions and the TBM’s specifications. Further multiple regression analysis then determines the interactions between six operational actions and ten mechanical responses. Operating procedures are established, and interlock and warning alarm systems are designed for use in the operating model. Lastly, several simulations were tested for the operating model of the TBM simulator under various conditions.

Pre-grouting for CHI of EPB shield TBM in difficult grounds: a case study of Daegok-Sosa railway tunnel

Pre-grouting for CHI of EPB shield TBM in difficult grounds: a case study of Daegok-Sosa railway tunnel

The influence of face and shield annulus pressure on tunnel liner load development

Three dimensional (3D) finite-difference analysis simulations together with rare field data from strain gauges installed in segmental lining rings at the Seattle Sound Transit Northgate Link tunnel project are examined to provide a better understanding of segmental liner loading developed during earth pressure balance shield tunneling. A simplified 3D numerical model is presented for pressure balanced mechanized tunneling, where the annulus between the shield and excavated ground is full of pressurized material, simplifying the shield shape, and the modeling of the annular gap. This simplified model is based on the assumption that the shield annulus pressure controls the tunnel convergence prior to lining installation. While the presented model simplifies the modeling of the TBM shield, it captures the important components in shield tunneling, including the jointed segmental lining, grout injection pressure, time-dependent grout hardening, and the non-liner soil behavior using the hardening soil constitutive model. The results of this study show that the final lining loads are controlled by the chamber pressure for pressure balance TBMs with pressurized material in the shield annulus. In the case study presented here, pressure drops of the chamber pressure (common in EPB tunneling due to excavation standstill), result in a significant influence on tunnel lining loads.

Looking inside TBM parameters: feedback from the Tunnel 4 case study, Angat Water Transmission Improvement Project (Philippines)

The use of TBMs in the tunnel industry has undergone a continuous growth over the last years, with application in ever expanding ranges of geotechnical conditions. Nevertheless, the feedback from completed projects with respect to the use of machine data for assessing geotechnical conditions are not common: there are only a few attempts to correlate machine data with geotechnical conditions during excavation and in most cases the use of machine data is related to assessment of TBM performance for prediction of advance rate. The analysis of TBM parameters may represent an interesting tool for monitoring of geotechnical conditions at the tunnel face and early detection of adverse face conditions. This work presents the feedback from the Tunnel 4, a 6.4 km long water transfer tunnel excavated by double shield TBM in the Philippines. The machine data have been analysed for identification of most sensitive parameters to geomechanical properties of the rock mass. In this respect, the use of specific-excavation parameters provides best results for assessing geotechnical conditions during excavation. Specific energy and Field Penetration Index displayed a good correlation with RMR values. The combined use of Net Advance Rate and Drillability Index allows to highlight how unstable face conditions and / or tough rock can influence the TBM advance.

A Combined Discrete Element-Finite Difference Model for Simulation of Double Shield TBM excavation in Jointed Rocks

A Combined Discrete Element-Finite Difference Model for Simulation of Double Shield TBM excavation in Jointed Rocks

A study on the soil conditioning behaviour according to mixing method in EPB shield TBM chamber

A study on the soil conditioning behaviour according to mixing method in EPB shield TBM chamber

Systematic Performance Evaluation of Shield TBM Cutters for Excavating Multiple Soft Rock

Cutter performance evaluation is important for shield TBM during the design and refurbishment stage. To face the challenges of choosing the proper cutters for tunneling in complex condition, according to the concept of parameter profile analysis, a systematic evaluation method was proposed. In this novel method, by comparing with their expected best value and the corresponding unacceptable limit, all of the selected performance parameters can be synthesized to assess the proximity of the overall merit of each cutter with respect to all the performances considered under all possible geological conditions. Performance indexes including cutting efficiency, structural strength, wear life, and dynamic response were individually analyzed based on linear cutting tests, finite element analyses, and theoretical calculations. Finally, a case study was carried out to demonstrate how the method is applied to find the optimal cutter among a small-scale disc cutter and two scrapers used for cutting multiple soft rock. In this case, three types of concrete specimens with distinct mechanical properties were carefully prepared to substitute for soft rock. The evaluation results show that the method has an intrinsic applicability in helping to make a reasonable trade-off between cost and cutting performance during the cutter selection process.

Control and prevention of gas explosion in soft ground tunneling using slurry shield TBM

For biogenic gas-rich ground tunneling, control and prevention of gas explosion is an arduous task. Until now, there is still a lack of reliable technologies to eliminate security emergencies such as explosion and combustion. In the present study, geotechnical investigations associated with the biogenic gas-rich ground at Sutong GIL Yangtze River Crossing Cable Tunnel have been summarized. The potential pathways for biogenetic gas to penetrate into the shield TBM and the excavated tunnel have been analyzed. Then, the adverse effects of biogenic gas on slurry shield TBM and tunnel construction progress have been evaluated. Finally, solution schemes including bentonite slurry penetration, clay shock method, gas detector system, explosion proof design, gas extraction system and wireless communication system have been proposed to mitigate the risk of biogenetic gas leakage and explosion. The application of these technologies has enabled the safety construction of long distance cross-river tunnel in organic-rich marine sedimentary ground.

A preliminary study for numerical and analytical evaluation of surface settlement due to EPB shield TBM excavation

A preliminary study for numerical and analytical evaluation of surface settlement due to EPB shield TBM excavation

Analysis on the excavation management system of slurry shield TBM in permeable sandy ground

Slurry shield TBMs with full-face mechanized excavation and active face support using slurry suspension are increasingly being employed for the construction of underwater tunnels. When tunneling in permeable sandy ground, the choice of suitable excavation management system and volume calculation method is extremely important to prevent security emergencies such as face collapse, water inflow and ground deformation. However, this subject has not attracted adequate attention in previous studies. Until now, there is still a lack of reliable methods to calculate geomaterials excavated from the tunnel face in permeable sandy ground. In the present study, shortcomings of traditional calculation method have been analyzed. Improved calculation method considering the effect of slurry filtration loss and ground water displacement has been proposed to evaluate the performance of excavation management system in permeable sandy ground. A case study of Sutong GIL Yangtze River Crossing Cable Tunnel has been carried out. The results indicate that the calculation error based on the improved method is smaller than that based on the traditional method. The improved method is much more suitable for permeable sandy ground.

Development and Application of Cutterhead Working Status Monitoring System for Shield TBM Tunnelling

During the shield TBM tunnelling, the working status of the cutterhead is difficult to be determined because the pressured chamber is located behind the cutterhead. In this paper, a cutterhead working status monitoring system for shield TBM tunnelling was developed to monitor the working status of the cutterhead in real time. The system consists of data acquisition subsystem, control and data transmission subsystem, as well as data processing and display subsystem. The cutter wear, cutter rotation speed and cutterhead temperature can be monitored and transmitted to the system software through the central port by cable and wireless. The system software can simultaneously display the TBM operating parameters and cutterhead working status parameters, predict the cutter life and present early warning of abnormal working status. The system has been successfully applied in a shield tunnelling project. Based on the analysis of the monitoring data, it was found that the normal cutter wear mainly depended on the rock abrasiveness and cutter rotation distance. The difference in cutter wear rate in the different ground was more than 3 times. The relative sliding between the cutter and the tunnel face was widespread. The sliding distance in low-abrasive formations exceeded 1/3 of the cutter track length. Under the normal tunneling conditions, the cutterhead temperature was lower than 50°. The successful application shows that this system can work stably in long term under harsh work environment and provide guidance for shield TBM tunnelling.

Research on Guidance Method of Double Shield TBM Based on Monocular Vision

Research on Guidance Method of Double Shield TBM Based on Monocular Vision