Shield TBM Research Articles

Actual performance analysis of a double shield TBM through sedimentary and low to medium grade metamorphic rocks of Ghomrood water conveyance tunnel project (lots 3 and 4)

In this paper, after a brief description of engineering geological properties of Ghomrood water conveyance tunnel project (lots 3 and 4 with a total length of 18 km), the actual performance of the machine during the excavation of tunnel through sedimentary and low to medium grade metamorphic rocks has been analyzed. Subsequently, using data collected during pre-construction and construction phases of the project, the relationships between rock mass properties and measured machine performance parameters have been investigated and proposed as a prediction model which can be used in future projects in which similar geological conditions are encountered. Results of analyses indicated that there are strong relationships between TBM performance and engineering geological conditions of the tunnel alignment.

Research on Water Inrush Disaster Control Technology in Double Shield TBM Excavation Process

Taking the TBM water inrush accident in An-Xue section of Qingdao Metro Line 1 as the engineering background, the research is carried out from two aspects of TBM water inrush emergency measures and grouting reinforcement treatment technology, which can ensure the strength of stratum reinforcement and water shutoff, and at the same time prevent the slurry from damaging the cutter head. For different areas, the grouting construction technology is proposed. After the reinforcement, the water stopping effect is obvious, the water inrush point has no water flow out, the hole drilling effect is good, the core removal rate is 75%∼85%, and the strength meets TBM excavation requirements.

계측 자료 분석을 통한 EPB쉴드 TBM의 막장압에 관한 연구

본 연구에서는 터널 굴착시 막장의 안정성과 지상부의 안정성 확보를 위하여 막장압에 영향을 주는 요소들에 대하여 막장압 현장 계측 자료를 분석하고 막장압 추정식을 도출하고자 하였다. 지하수위와 막장압간의 상관관계 분석결과 하저구간의 막장압이 매우 크게 나타나는 것을 알 수 있었다. 이는 지형적 특성상 하저구간은 한강 수두면까지의 압력이 막장압으로 작용하였기 때문인 것으로 판단된다. 본 연구에 적용된 현장은 육상부와 한강하저구간으로 구분할 수 있으며, 초기의 굴진 계측자료들을 이용하여 향후 굴착시 발생가능한 막장압을 계측할 수 있었다.

Evaluation and Optimization of the Effective Parameters on the Shield TBM Performance: Torque and Thrust—Using Discrete Element Method (DEM)

Cutterhead torque and thrust are the two main designing parameters of the shield TBM, which have to be evaluated and optimized, based on the interaction between the TBM and excavated material. This study employs the discrete element method (DEM) to simulate the tunneling procedure of the line-7 of Tehran underground urban train tunnel utilizing the micro mechanical parameters calculated from back analysis on direct shear tests. The resultant torque and thrust are then compared against the actual parameters and then with those estimated from the numerical analyses. This result shows that DEM is able to estimate the TBM torque and thrust applying actual boundary conditions and material properties for the model. Furthermore, the impact of ground properties, overburden height, linear and radial velocity on cutterhead torque and thrust and its performance are evaluated and optimized.

双护盾TBM超前支护系统设计

双护盾TBM超前支护系统设计

Development of a TBM Advance Rate Model and Its Field Application Based on Full-Scale Shield TBM Tunneling Tests in 70 MPa of Artificial Rock Mass

Development of a TBM Advance Rate Model and Its Field Application Based on Full-Scale Shield TBM Tunneling Tests in 70 MPa of Artificial Rock Mass

Prediction and analysis of replaceable scraper wear of slurry shield TBM in dense sandy ground: A case study of Sutong GIL Yangtze River Crossing Cable Tunnel

Prediction and analysis of cutting tool wear in dense sandy ground is important for improving the working performance of slurry shield TBM, especially for long-distance cross-river tunnel. Appropriate prognosis model can not only improve the construction efficiency, but also avoid the risk from cutterhead inspection and tool maintenance which are difficult, time-consuming but necessary procedures. Although several prognosis models have been utilized for estimating cutting tool wear, these models have inherent mismatches with actual geological conditions of tunnel projects. In order to promote the predictability of cutterhead inspection and tool maintenance, empirical prognosis model suggested by the Japanese Society of Civil Engineers (JSCE) has been improved by proposing a new method for the calculation of the wear coefficient in heterogeneous ground. Compared with initial model, the improved model takes into account the influence of stratigraphic change along the tunnel alignment on the wear coefficient. Hence, it is more applicable and accurate. A case study on the prediction and analysis of replaceable scraper wear in dense sandy ground at Sutong GIL Yangtze River Crossing Cable Tunnel has been carried out by using the improved model. The predicted value is comparable with the actual value in terms of wear coefficient and wear extent.

A HEADRACE TUNNEL RECONSTRUCTION IN TURKEY

The operation of a hydro power project in North Turkey started in 2015, included the 12km long headrace tunnel. An 8km long lower tunnel section was excavated by double shield TBM technology with 8.7m ID. Due to problems with the mechanised excavation, a 4km long upper tunnel section was excavated conventionally by the Drill and Blast method with single shell lining generated from fibre reinforced sprayed concrete and rock bolts. Significant operational problems were observed in September 2016. The flooded tunnel was investigated by underwater Remotely Operated Vehicle which indicated significant collapses. Operation of the power station had to be stopped and water from a supply dam at the headrace tunnel inlet had to be discharged to enable dewatering and inspection of the tunnel. Consequent investigation revealed three major collapses and a considerable variety of other damages in the D&B section of the tunnel. Repair and strengthening of the tunnel was completed in October 2017.

Numerical analysis of hard rock tunnel excavated by double shield TBM based on CWFS model

In order to study the mechanical response of a hard rock tunnel excavated by double shield tunnel boring machine (DS-TBM), a numerical method was introduced to simulate the TBM excavating process. The failure modes of surrounding rock mass described based on the cohesion weakening and frictional strengthening (CWFS) Mohr-Coulomb strain-softening criterion. The characteristics of stress field and plastic zone on the cross and longitudinal section of the tunnel were analyzed in detail, and the results were compared with those in the intrinsic condition (when TBM model is not activated). The simulation results indicate that the stress paths at the vault are relatively simple, and the stress concentration caused by excavation unloading is obviously reduced by lining and backfill grouting, while the sidewall is less disturbed by the excavation of TBM. The invert experiences three unloading processes, due to excavation, the contact between the rear shield and the bottom of surrounding rock, as well as backfill grouting at gap between the lining and the rock mass. The vault has a larger plastic zone than the invert, attributing to the geometrical difference between the cutter-head and the front shield, as well as the conicity of the front and rear shields. The area of plastic zones gradually increases along the tunnel route, but it becomes stable after the rear shield.

Slurry Clogging Criteria for Slurry Shield Tunnelling in Highly Permeable Ground

When tunnelling using a slurry shield tunnel boring machine (slurry shield TBM), the tunnel face stability is significantly influenced by the filter cake formation during slurry injection to the chamber. In order to study slurry penetration behavior in highly permeable ground, comprehensive slurry injection tests were performed by varying the particle size distribution of the ground, the bentonite content and viscosity, and the slurry injection pressure. According to the results of these tests, the slurry penetration behavior could be classified into three types: Type A, denoting negligible slurry penetration; Type C, denoting excessive penetration; and Type B, denoting in-between penetration. Slurry clogging criteria (SCC) were proposed to classify these three types. The main superiority of the proposed SCC is that it can consider the grain size distribution of the ground, the characteristics of the slurry, and the slurry injection pressure together when assessing the penetration characteristics. The SCC value can either be obtained by performing a simple slurry penetration test; or it can be theoretically estimated by using the regression equation proposed in this paper.

Response of the ground and adjacent end-bearing piles due to side-by-side twin tunnelling in compound rock strata

Considering that the subway tunnelling projects in the Chongqing region are located in strata dominated by sandstone and mudstone, the main empirical construction parameters (excavation thrust = 5 880 ∼ 6 860 kN, average pea gravel content (APC) ≥ 85%, and grouting pressure (GP) = 0.3 MPa) were obtained by engineering surveys; these empirical parameters were similar to those optimized under interval tunnel construction conditions. Additionally, a simulation method was developed based on the construction characteristics of a single shield TBM by using the ADINA software to simulate the construction process of subway tunnels undercrossing the pile foundations (end-bearing piles) of an old surface building in the composite strata of the Chongqing Rail Transit Loop Line. A sensitivity analysis was performed on the calculation parameters first because the changes in the stratigraphic and TBM construction parameters greatly influenced the calculation results. Then, we used the modified calculation parameters to study the effects of tunnel construction on the settlements of the ground surface and pile foundations in the composite strata, and these effects were compared to the field monitoring results. The results showed good agreement between the numerical calculations and the monitoring findings. Thus, the methodology and empirical construction parameters adopted in this paper can provide a reference for the construction of other tunnel sections of this project in similar construction conditions.

Research on TBM type selection risk for long draw water tunnel

The draw water tunnel of west line project is composed by tunnels group, the longest tunnel section is 73km, belonging to the super long tunnel. The tunnel construction method is TBM. The engineering geology and hydrological geology is complex along the tunnel, facing a lot of engineering geological problems in the excavation process, such as water inrush and rock burst. Through the TBM type selection factors analysis in West super long tunnel, drilling and blasting method and TBM methods are compared, the advantages and disadvantages between shield TBM and open type TBM are also be compared, the double shield TBM is selected as the construction machinery. At the end of the analysis, the adaptability to the formation of TBM is analyzed, and the improvement measures of TBM is put forward.

A Study on the Stability of Shield TBM Thrust Jack in the Behavior of Operating Fluid According to Thrust Force

A Study on the Stability of Shield TBM Thrust Jack in the Behavior of Operating Fluid According to Thrust Force

An Improved 3D Finite Difference Model for Simulation of Double Shield TBM Tunnelling in Heavily Jointed Rock Masses: the DXL Tunnel Case

An Improved 3D Finite Difference Model for Simulation of Double Shield TBM Tunnelling in Heavily Jointed Rock Masses: the DXL Tunnel Case

Favorable driving direction of double shield TBM in deep mixed rock strata: numerical investigations to reduce shield entrapment

In deep mixed rock strata, a double shield TBM (DS-TBM) is easy to be entrapped by a large force during tunneling. In order to reduce the probability of the entrapment, we need to investigate a favorable driving direction, either driving with or against dip, which mainly associates with the angle between the tunneling axis and strike, theta, as well as the dip angle of rock strata, a. We, therefore, establish a 3DEC model to show the changes of displacements and contact forces in mixed rock strata through LDP (longitudinal displacement profile) and LFP (longitudinal contact force profile) curves at four characteristic points on the surrounding rock. This is followed by a series of numerical models to investigate the favorable driving direction. The computational results indicate driving with dip is the favorable tunneling direction to reduce the probability of DS-TBM entrapment, irrespective of theta and a, which is not in full agreement with the guidelines proposed in RMR. From the favorable driving direction (i.e., driving with dip), the smallest contact force is found when theta is equal to 90o.The present study is therefore beneficial for route selection and construction design in TBM tunneling.

Numerical Study on Medium-Diameter EPB Shield TBM by Discrete Element Method

Numerical Study on Medium-Diameter EPB Shield TBM by Discrete Element Method

Investigation of the excavation damaged zone around deep TBM tunnel using a Voronoi-element based explicit numerical manifold method

A Voronoi-element based explicit numerical manifold method is adopted to investigate the evolution process and failure characteristics of the excavation damaged zone around a deeply buried TBM tunnel. An explicit time integration scheme of numerical manifold method is adopted as the numerical platform, based on which a Voronoi polygon assemblage is generated to approximate the blocky structure of the surrounding rock mass resulting from discrete fracture networks. A new mathematical mesh generation method is developed to better adapt to the Voronoi polygons and an excavation algorithm including both in-situ stress equilibrium and TBM excavation modelling techniques is proposed to capture the mechanical response of the TBM tunnelling process. With the newly developed VE-ENMM approach, the progressive failure process of the surrounding rock mass in a headrace tunnel of Yindajihuang Project is simulated and the formation mechanism of the excavation damaged zone is explored. Simulation results show that a large extent of excavation damaged zone is easily formed in the highly fractured rock mass due to the high in-situ stress in deep grounds. Besides, relatively large convergence displacements are predicted around the tunnel surface, leading to a high risk of TBM shield jamming as in the practical situation. However, the development of damaged zone is effectively restrained and the convergence displacements are well controlled by an early installation of the tunnel lining segments, thus preventing the occurance of TBM shield jamming. Additional simulations are conducted to study the effects of the lateral in-situ stress ratio on the excavation damaged zone. It is inferred that the increase of lateral stress ratio facilitates the fracturing of the surrounding rock mass, which results in a larger extent of the damaged zone and more severe squeezing deformation compared with those under lower lateral stresses.

Bedding improvement of lining segments using geotextile tubes

AbstractDuring a shield TBM excavation in hard rock, the immediate backfill of the crown immediately behind the shield is technically difficult to realize. With the advance of the cutter head a relocation process of pea gravel within the annular gap is triggered, leading to an insufficient bedding distribution of the first segments behind the shield tail and to an ovalization of the segmental lining at a certain load level. During a test application as part of an ”TBM research initiative“ of the Austrian Federal Railways geotextile tubes were integrated into the exterior surface of the segments. Immediately after leaving the shield tail, the geotextile tube, which is placed all around one ring of segments, is expanded by injection with grout. As a result, an immediate bedding between the rock mass and segmental lining is established, also preventing the rearrangement of pea gravel within the annular gap when the shield is moved forward. The displacement measurements have shown that the ring of segments equipped with geotextile tubes experiences a more rigid body motion like behaviour after leaving the shield tail with a minimal ovalization only. Numerical simulations show the influence of bedding improvement on the ovalization of the ring of segments after leaving the shield tail.

Influence of the slurry-stabilized tunnel face on shield TBM tool wear regarding the soil mechanical changes – Experimental evidence of changes in the tribological system

The wear of slurry shield TBM excavation tools is a challenging topic that has been discussed over many years, Due to the complexity of the tribological system that defines the tool wear, no sufficient approach to determine the wear in a specific tunneling project has been developed up to now. The elementary step to display the application-oriented tribological system is one of the main issues regarding laboratory scale test methods. Therefore, the RUB Tunneling Device has been developed at the Ruhr-University Bochum (Germany). With this apparatus, several influencing factors regarding the tribological system of a TBM-tool can be analyzed. A unique feature of the device is the experimental simulation of a slurry shield excavation, including a realistic tunnel face support. This paper focuses on the experimental simulation of slurry shield excavation and the influence of face support on tool wear. Changes in the soil mechanical properties due to slurry penetration at the tunnel face are regarded and correlated with the tribological system of a slurry shield excavation. It is proven that the tribological system, and thus the tool wear, changes significantly due to slurry injection.

Parametric study of the impacts of various geological and machine parameters on thrust force requirements for operating a single shield TBM in squeezing ground

Excavation of long tunnels by shielded TBMs is a safe, fast, and efficient method of tunneling that mitigates many risks related to ground conditions. However, TBM applications in difficult conditions such as squeezing ground, which often happens in a combination of weaker rock and/or high depth, may lead to problems such as shield jamming. Insufficient thrust force, which cannot overcome the shield skin friction between the machine and the ground, causes shield entrapment. For successful tunneling in such conditions, it is essential to study the pertinent ground and operational factors and their impact on ground behavior, to assess the possibility of shield entrapment and to develop possible safeguards to mitigate the related risks. In this study, the controlling parameters influencing the risks of tunneling by single shield TBMs in squeezing ground are examined. For this purpose, a parametric study was performed by using a full 3D numerical simulation to quantify the influence of various factors on machine entrapment. Sensitivity analysis of most important parameters and their impacts on entrapment risks has been conducted and the results are discussed in this paper. Furthermore, nonlinear regression analysis was performed to develop a relationship between ground and machine parameters, and the required thrust force needed to overcome contact/frictional forces for propelling machine forward. The result of the modeling was compiled in a database to observe the trends and develop relationship between different parameters and risk of machine entrapment. This allows for assessment of the applicability of shield TBM in weak formations along the tunnel. Furthermore, the results of the analysis can be used to evaluate the operational parameters such as the installation of a higher thrust force to overcome contact friction loads and to make a choice between increasing the overcut or using lubricants between shield and ground. The results of this study show the role of ground conditions and in-situ stresses, as well as machine operational parameters on convergence and shield pressures.