Tunnel Boring Research Articles

Dynamic analysis and experimental study of a Tunnel boring Machine testbed under multiple conditions

The main drive system is the core of a Tunnel Boring Machine (TBM). The force transmission law of this system is extremely complicated, which leads to severe vibration, structural failure, and safety hazards. Therefore, the dynamic analysis and the study of the vibration transmission law of a TBM main system under different working conditions are very important. In this study, a novel testbed for a hard rock TBM main system and a multi-DOF coupling dynamics model were built by considering the external excitations of the cutters, the time-varying meshing stiffness of the gear teeth, the meshing error, the clearance, and the stiffness of the main bearing. A wireless vibration monitoring system was built on the testbed. Experiments under typical working conditions were done to verify the dynamic model. Finally, the dynamic response of the system was analyzed. The results showed that the maximum error of the theoretical and actual dynamic response was 18.1%, and the dynamic model could be used to analyze the vibration of an actual TBM. The vibration law of the testbed was close to the actual TBM, so the testbed could be used for the vibration law analysis of the actual TBM under other working conditions. The study of the vibration law under different working conditions and different digging parameters could be used to guide the intelligent tunneling of the TBM.

Predicting Tbm Performance for Pila Spi Formation in Qara Dagh Anticline, NE Iraq

There are a few studies on the engineering properties of the Pila Spi Formations in scattered areas of Northern Iraq, but there is no study on predicting the performance of Tunnel Boring Machines (TBM), which is of great importance in future large engineering projects in Iraq. The study area is located on the Takya about 50 km south the center of Sulaimania City. Field and laboratory studies were conducted on five (5) selected sites situated in the southwestern flank of the Qara Dagh anticline. The axis of the anticline extends from NW-SE of Iraq with a length of roughly 116 km. The engineering and field results of the samples collected from different locations indicate that the compressive strength of the rocks having a fine texture and slightly weathered characteristics ranges between strong to very strong with high dry density and low moisture content. In addition, the average Schmidt hammer rebound and weight losses percentages of Lose Angeles values are 48 and 22%, respectively the sizes of the blocks range from large to very large, the spacing of the discontinuities is medium to wide. The performance of TBM in terms rate of advance is generally determined based on these geological rock materials and masses. To estimate the rate advance of boring machine (TBM) in this study, the method depends on the total hardness. After applying the total hardness method, it was estimated that the predicted rate of advancement of the TBM would be very slow (approximately 1.57 -1.86 m/hr) due to the strong hardness of the rocks of Pila Spi Formation.

Tunnel Boring in Infrastructure Projects will Thrive from the Use of Construction Robots, Advanced Technological Innovations, and Artificial Intelligence.

India will become the fastest-growing tunnel construction market in the next five years, thanks to rapid growth in metro, rail, road, and hydropower projects. Even though tunnel construction started in India in the nineteenth century, little is known about the factors that affect tunnel performance and their effect on project completion. This is demonstrated by the time and cost overruns of major tunnelling programs. These aspects, as well as the use of construction robots and advanced digital technology to increase TBM performance by developing and performing a more efficient tunnelling process, are examined in the study. In the current phase, the factors have been identified by comprehensive literature exploration, and a questionnaire will be sent to tunnelling experts to study the factors and their rated importance. Case studies of a similar nature will be used to validate the model, and conclusions will be drawn. Contractors should forecast the length of time and cost of tunnelling programs based on their efficiency, considering the arbitrary effect of variables. The factors that drive the use of construction robotics and advanced technologies to improve efficiency are also addressed.

Geotechnical Characterization and Applications of Riyadh Metro Tunnel Boring Machine Excavated Material (TBMEM)

The Riyadh city is witnessing one of the most significant infrastructure projects in its history. The 22.5 billion dollars and 180 km in total length Riyadh Metro project will be constructed using different tunnelling methods: 10 m diameter tunnel boring machine (TBM), cut and cover, and new Austrian tunnelling method (NATM). About 35 km will be constructed using 10 m diameter TBMs, which will produce approximately 2.8 million cubic meters of TBM excavated material (TBMEM). Transferring such an amount of material will cause a severe impact on the environment and traffic as it required many trucks to transport the material to a remote site. The comprehensive geotechnical characterization profile of the material was prepared in order to understand the performance of the material and identify the areas in which the material can be utilized. In addition, this paper will explore the potential of using TBMEM after being treated and mix with clean sand to enhance its geotechnical characteristics. Several potential areas to utilize the TBMEM will be presented. Furthermore, the project will investigate the applicability of TBMEM to be used as backfill material and to what extent the treatment should go to achieve a mixture that meets the standard requirements.

Short and Long-term Behaviours of Bored Tunnels in Port-Said Clay

This study investigates the behaviour of bored tunnels in the Port-Said very soft to firm clay deposit in El-Tina Plain, north-eastern Egypt. Recent studies provided full characterization of the physical, mechanical and time-dependent properties of Port-Said Clay. This characterization enabled simulating its constitutive behaviour using the stress-dependent Modified Cam Clay model. The finite difference method is utilized to simulate the interaction between the tunnel and Port-Said Clay. The results are presented in terms of the pore water pressure regime, shear strain level, ground surface settlement and tunnel lining bending moment. The results show significant effect of the face and grouting pressures on the tunnel’s short and long-term behaviours. The term “reference hydrostatic pressure” is introduced to evaluate short-term face stability as a more practical and easy-to-quantify parameter compared to the conventional stability number. New empirical equations are developed to describe the long-term surface settlement trough (maximum settlement and trough width) in terms of the grouting pressure and tunnel diameter for tunnels in similar soft clay deposits.

Performance Analysis of Tunnel Boring Machines for Rock Excavation

The study takes into account different classes of tunnel boring machines (TBM), with the aim of identifying correlation models which are meant to estimate, at a preliminary design phase, the construction time of a tunnel and to evaluate the mechanical and operational parameters of the TBMs, starting from the knowledge of the tunnel length and the excavation diameter. To achieve this goal, first of all a database was created, thanks to the collection of the most meaningful technical parameters from a large number of tunnels; afterwards, it was statistically analyzed through Microsoft Excel. In a first phase, forecasting models were identified for the three types of machines investigated, separately for compact rocks (open TBM) and fractured rocks (single and double shield TBM). Then, the mechanical parameters collected through the database were analyzed, with the aim of obtaining models that take into account, in addition to the type of TBM, the geological aspect and the type of rock characterizing the rock mass. Finally, the validation of the study was proposed in a real case, represented by the Moncenisio base tunnel, a work included in the new Turin–Lyon connection line. The estimated values were compared with the real ones, in order to verify the accuracy of the experimental models identified.

Analysing the Feasibility of a\xa0Full-face Cutting Machine for the Robominers Project

Several methods of excavation have previously been studied to choose the most suitable approach to be applied in the Robominers project. Compared to drilling and blasting and partial-face cutting, the full-face cutting option is regarded as one of the methods which can offer, among others, high advance rates and a safer working environment for the machinery. Current technologies of these methods, however, suffer from several limitations, such as the inability to bore very hard rocks, significant lack of geometrical flexibility in mine working areas, and low mobility due to large and heavy components. In this study, two of the most commonly applied small diameter full-face machines including the pipe jacking and the Boxhole Boring Machine (BBM) are studied with regards to their performance parameters. The pipe jacking machine option with a cutterhead consisting of disc cutters exhibits higher efficiency in excavation with only slightly lower production rates compared to a BBM with strawberry cutters. They are also much lighter machines. Yet, using the jacking concept means a limited driving length and does not apply to the Robominers. Therefore, the introduction of small gripper or shielded Tunnel Boring Machines (TBMs) can significantly improve the mobility. Their application, however, requires considering the risks of jamming in difficult ground conditions and the possible requirements of a support installation. These rock mechanics issues need to be carefully considered in the design of such machines. In addition, further studies are required to employ assisted cutting methods in very hard rocks and to increase the geometrical flexibility of these machines by lowering their turning radius.

Study on Optimum Free-face Condition of Cutting Hard Rock with Tunnel Boring Machine Hob

To explore the rock-breaking characteristics of cutting hard rock under free-face condition by tunnel boring machine (TBM) hob and obtain the optimum free-face condition, the rock-breaking processes such as crack propagation, amount of micro crack and reaction force with penetration depth are first investigated based on discrete element simulation method. Then, the crack length, rock chip area, specific energy consumption etc. with different free-face spacing (S) and free-face height (H) are studied combined with rock-cutting simulation and experiment. The research results show that the formation of the rock chip under free-face condition by TBM hob is driven by tensile failure, and it exists an optimum free-face condition with the S of 80 mm and the H of 200 mm to promote main crack propagation and enhance the rock-cutting efficiency, which can provide a reference for the application of rock-breaking technology under the free-face.

Research Progress on Big Data of Tunnel Boring Machine: How Data Mining Can Help Tunnel Boring

Research Progress on Big Data of Tunnel Boring Machine: How Data Mining Can Help Tunnel Boring

Analysis of Grinding and Chipping Processes beneath Disc Cutters of Hard Rock Tunnel Boring Machines (Case study: Uma-Oya water Conveyance Tunnel, SriLanka)

Analysis of Grinding and Chipping Processes beneath Disc Cutters of Hard Rock Tunnel Boring Machines (Case study: Uma-Oya water Conveyance Tunnel, SriLanka)

Three-Dimensional Modeling and Analysis of Mechanized Excavation for Tunnel Boring Machines

Three-Dimensional Modeling and Analysis of Mechanized Excavation for Tunnel Boring Machines

Interaction of cutting disc with heterogeneous ground

AbstractIn this contribution, the peridynamic theory [1] is utilized to analyze the interaction of cutting disc of a Tunnel Boring Machine (TBM) with mixed (heterogeneous) ground conditions. Peridynamic formulations, in contrast to classical continuum theory, do not contain spatial derivatives [1,2], which makes it a preferable tool for modeling phenomena involving discontinuities, such as complex fracture and fragmentation processes [3]. The model was initially used to simulate a full‐scale Linear Cutting Machine (LCM) test for various penetration levels [4]. The cutting forces obtained were in agreement with the experiment [5]. Excavation process in mixed ground conditions is analyzed using simulations in which a cutting disc moves from a soft ground (soil, weathered rock or soft rock) region into a hard rock region. There is a sudden increase in the force on the cutting disc as it moves from a soft to hard ground, this abnormal peak in force is further investigated with respect to various tool penetrations.

Dispersant for Reducing Mud Cakes of Slurry Shield Tunnel Boring Machine in Sticky Ground

When a slurry shield tunnel boring machine (TBM) encounters sticky ground during tunneling, mud cakes often occur on the cutter head due to the high stickiness of soil. The mud cakes caused several negative issues, such as high torque demand, advancement rate reduction, and additional costs. Existing studies have largely focused on Earth pressure balance TBMs; research on formation and mitigation measures of mud cakes in slurry shield TBMs is limited. Therefore, this study proposes the addition of dispersant to the slurry to prevent mud cakes during the tunneling of slurry shield TBMs by reducing stickiness of excavated clay. The basic properties of slurry were measured experimentally, and the effectiveness of dispersant in reducing the potential for mud cakes was investigated through mixing tests and viscosity experiments. A statistical analysis of the data was performed to determine relationships between slurry properties and material behaviors. The results showed that the slurry with dispersant had a lower viscosity and formed filter cakes more quickly, thereby meeting the performance requirements of a supporting fluid for slurry shield TBMs. Further, dispersant effectively reduced the empirical stickiness ratio and suspension viscosity. Therefore, a slurry with an appropriate dispersant content could effectively reduce the potential for mud cake formation.

Identification of the actual excess excavation ratio (Stakhanovskaya street – Nizhegorodskaya street site)

Introduction. Redundant strain arises in buildings and structures in areas of construction work influence caused by the deep bore tunneling performed by tunnel boring machines. The strain analysis must include an excess excavation ratio that depends on the structural features of the shield, the technology of grouting mixture injection outside the lining, the counterweight pressure applied to the shield face and geotechnical conditions so that excessive settlement could be taken account of. The purpose of the article is to identify actual values of the excess excavation ratio to raise excavation and determine the values of standard averaged excess excavation to be further applied in design.
 Materials and methods. This paper focuses on tunnel driving between “Stakhanovskaya Street” and “Nizhegorodskaya Street” stations. The project excess excavation ratio was applied pursuant to the regulatory documents in order to perform the analysis using PLAXIS 2D and PLAXIS 3D software packages. The method of sequential iteration was applied to identify the value of excess excavation in line with the actual settlement of buildings and structures obtained by means of monitoring.
 Results. The analysis has shown that the actual excess excavation ratio varies between 0.1 and 1.2 % for this construction site which is below the values required by the regulatory documents. As for the 3D setting, the values of actual excess excavation ratios are 2 to 4 times higher than those obtained for the 2D setting, although the value of the actual building settlement remains the same.
 Conclusions. Since the actual building settlement is smaller than the projected one, the cost of deep bored tunneling can be reduced by cutting the cost of protection of nearby buildings and structures within the area of tunneling influence without violating any safety requirements and also by reducing the number of buildings withing the projected area of influence, and respectively, by reducing the cost of geodetic monitoring over their displacements.

Rock Breaking Performance of Two Disc Cutters of Tunnel Boring Machine for Safe Tunneling in Unstable Coal Rock Stratum

In unstable coal rock formations, the rescue channels should be constructed through safe and efficient tunneling. The rock breaking performance of the tunneling equipment directly hinges on the cutter-head layout. Focusing on the conditions of unstable coal rock formation, this paper adopts the extended Drucker-Prager (D-P) plastic model to define the properties of bedrock materials of the coal rock with low mechanical strength and poor homogeneity. Then, a finite-element model was established on ABAQUS for the coal rock cut by two disc cutters, and used to simulate the breaking of the coal rock and the peeling of slags from the bedrock. On this basis, the authors analyzed the influence of cutter spacing (30, 35, 40, and 45mm) over cutting force, rock breaking amount, and specific energy under two cutting methods: simultaneous cutting and sequential cutting. Finally, a cutter deployment strategy was designed for safe and efficient tunneling in unstable coal rock formations. The results show that: Under simultaneous cutting, as the cutter spacing increased from 30 to 35mm, the rock breaking amount increased, while the specific energy declined; as the cutter spacing further rose from 35 to 45mm, the rock breaking amount dropped, while the specific energy increased. Under the coal rock conditions in our research, the optimal cutter deployment strategy is: simultaneous cutting with cutter spacing of 35mm. The research results provide theoretical support for the cutter-head design of rescue equipment for collapsed coalmines.

Land Subsidence due to Leakage of Aquitard-aquifer Pore Water in an Under-construction Tunnel of East-West Metro Railway Project, Kolkata

Palaeo-geographical conditions control the sedimentological and hydrological heterogeneity within the upper aquitard and late Pleistocene aquifers beneath Kolkata. Such complexity at Bowbazar was unmapped prior to the Tunnel Boring Machine (TBM) of East-West metro project which hit the local aquifer at 14 m depth. This led to development of cracks in tens of buildings due to land subsidence; few of which collapsed immediately, and some stood in such a precarious position to be eventually razed. Mass evacuation was undertaken from the area. This paper assesses the local hydrogeological conditions and hydrostatic pressure of the aquitard-aquifer system that caused the disastrous land subsidence.

Behaviour of FRC segments with GFRP cage under TBM thrust in presence of GAPs

Due to their structural performance and durability, Fibre Reinforced Concrete (FRC) precast segments are now commonly used in major tunnelling applications around the world. The paper investigates the effects of irregular loading on the segments due to poor alignment, which can occur on the tunnel lining during construction as a result of the operation of the Tunnel Boring Machine (TBM). During construction, as the TBM progresses, defects on the tunnel lining can arise. Cracks can then be caused by improper load application by the TBM thrust jacks (due to uncorrected inclination or eccentricities). Further defects can be caused by non-uniform ring joints and this needs to be taken into account in the design and construction of the lining. Because the precast segments are not supported uniformly by the previous ring, they are subjected to a transient bending moment that can jeopardise their integrity and performance during both the excavation phase and service life. The proposed hybrid solution of FRC segments with Glass Fibre Reinforced Polymer (GFRP) reinforcement presented in this paper can overcome these situations, which cannot be satisfied with FRC-only segments, by means of an “elastic-return action” provided by the GFRP reinforcement. Two full-scale tests simulating the TBM thrust, for which irregular support conditions were taken into account, were carried out. Based on the obtained results, it is concluded that the proposed hybrid solution shows almost full recovery of the initial geometry with residual crack widths measuring 79% less compared to the FRC-only solution.

A TBM advance rate prediction method considering the effects of operating factors

Due to the widespread use of Tunnel Boring Machines (TBMs) in China, all affected parties involved in related construction of projects have proposed higher requirements for the controllability of TBM construction periods. Consequently, this report proposes a new TBM advance rate prediction method. By mining TBM construction data obtained from a project diverting water from the Songhua River to cities in the middle region of the Jilin Province in China (hereinafter referred to as the “Songhua River Diversion Water Supply Project”) and analysing the varying rules of the tunnelling parameters under different surrounding rock conditions, this report proposes a corresponding relationship relating the surrounding rock conditions, reduction coefficient of the disc cutter thrust (Fn) and cutterhead rotation speed (N), and establishes a TBM penetration rate (PR) prediction model, which is affected by factors associated with the operator’s control. Furthermore, after investigating and summarizing the TBM construction processes of several projects, TBM downtime is classified and evaluated to obtain the TBM utilization factor (U). Based on the PR and U, a TBM advance rate (AR) prediction model is established. The established AR model was applied to a water diversion project in the Xinjiang Uygur Autonomous Region of China. This engineering practice has demonstrated that the operator adjusts the PR according to the surrounding rock conditions, and the prediction of the PR affected by the operating factors has been proven accurate. Furthermore, the prediction method of U obtained by evaluating the downtime is simple and feasible. Overall, the results indicate that the proposed AR model possesses satisfactory predictive performance.

Automatic Approach for Fast Processing and Data Analysis of Seismic Ahead-Prospecting Method: A Case Study in Yunnan, China

The seismic ahead-prospecting method is useful to detect anomalous zones in front of the tunnel face. However, most existing seismic detection method is designed for drilling and blasting tunnel. The detection method should be improved to satisfy the rapid tunneling of Tunnel Boring Machines (TBMs). This study focuses on reducing the time spent on seismic data processing and result analysis. Therefore, to reduce the data processing time, an automatic initial model establishment method based on surrounding rock grade is proposed. To reduce the time spent on result analysis and avoid subjective judgment, a modified k-means++ method is adopted to interpret the detecting results and extracting anomalous zones. The efficacy of the developed method is demonstrated by field tests. The fractured zones such as cavity collapse and fissure are successfully predicted and identified.

A Novel Intelligent Method for Predicting the Penetration Rate of the Tunnel Boring Machine in Rocks

In the construction of rock tunnels, the penetration rate of the tunnel boring machine (TBM) is influenced by many factors (e.g., geomechanical parameters), some of which are highly uncertain. It is difficult to establish a precise model for predicting the penetration rate on the basis of the influencing factors. Thus, this work proposed a useful method, based on the relevance vector machine (RVM) and particle swarm optimization (PSO), for the prediction of the TBM penetration rate. In this method, the RVM played a vital role in establishing a nonlinear mapping relationship between the penetration rate and its influencing factors through training-related samples. Then, the penetration rate could be predicted using some collected data of the influencing factors. As for the PSO, it helped to find the optimum value of a key parameter (called the basis function width) that was needed in the RVM model. Subsequently, the validity of the proposed RVM-PSO method was checked with the data monitored from a rock tunnel. The results showed that the RVM-PSO method could estimate the penetration rate of the TBM, and it proved superior to the back-propagation artificial neural network, the least-squares support vector machine, and the conventional RVM methods, in terms of the prediction performance. Moreover, the proposed RVM-PSO method could be applied to identify the difference in the importance of the various factors affecting the TBM penetration rate prediction for a tunnel.