Pilot Tunnel Research Articles

Optimization of Construction Method for Shijiazhuang Xinbai Subway Station

To choose an appropriate construction scheme for subway, it,s feasible to use fuzzy optimization theory and comprehensively consider the security of four construction methods as well as such factors as environmental influence, construction period, construction difficulty and construction cost, etc. to set up a mathematical model for the construction method of subway station. An analysis is made on the impact of group-effect in the excavation construction of pilot tunnel presented in PBA construction method on arch crown settlement and ground surface settlement, and a study is made on the arch crown settlement and ground surface settlement caused by the four construction methods in construction process. In addition, a contrastive analysis is made to draw a conclusion that PBA construction method is the most suitable construction method for Xinbai Square Subway Station in Shijiazhuang.

Numerical Optimization Analysis of the Construction Sequence of PBA Group Hole

Based on the PBA construction method of Changchun Liberation Road station metro line No.2, in order to get the optimization of construction sequence of six pilot tunnels, we use numerical simulation method and finite element software MIDAS GTS to establish the construction model of the station pilot tunnel. After comparing four excavation methods of the surface subsidence, we come to a conclusion that first up then down and first side then middle is the optimal excavation scheme. At the same time, we make models to analysis the necessity of making advance support before pilot tunnel construction. Pipe shed and small duct grouting pre support is very significant to the control of the subsidence of ground surface and vault.

Optimization Analysis of Different Excavation Offsets in Railway Pilot Tunnel by CRD Method

This paper focuses on the construction of 10 railway pilot tunnels by CRD method in Jiefang Road subway station in Changchun. To achieve the optimal construction offsets during the pilot tunnel excavation, reduce the impacts of group cavern effect, and maximize the production efficiency, the construction model of railway pilot tunnel in subway station was created by the finite difference software Flac3D. The author used the numerical simulation method to analyze the ground surface settlements and the stress variations with three different construction offsets. Then the optimal construction offset was obtained. It could provide a theoretical guidance to the construction of a similar project.

Excavation of the Aica-Mules pilot tunnel for the Brenner base tunnel: information gained on water inflows in tunnels in granitic massifs

The construction of the Aica-Mules tunnel, completed in 2010, provides a relevant case history for improving the knowledge of hydrogeological issues related to the excavation of deep tunnels in granitic massifs. The Aica-Mules tunnel is a 10 km-long structure, forming part of the high-speed railway connection between Austria and Italy across the Alpine chain, located at an average depth of 500–1,000 m below the surface. Prior to and during the construction, intense hydrogeological monitoring was set up, allowing the collection of abundant data concerning: (1) the evolution of water inflows into the tunnel; (2) the chemistry and temperature of drained groundwater; and (3) the influence of tunnel drainage on springs. Based on detailed analysis of geological/hydrogeological data, this article provides an insight into the permeability distribution in granitic rocks affected by relevant brittle tectonic deformation, and the consequences of water inflow during excavation. The available time series from the principal water discharges in the tunnel have been used in order to test the reliability of some of the most commonly applied analytical methods for the forecast of water inflows into tunnels.

The Comparison and Selection of the Solutions for Liuyang River Tunnel’s Inclined Shaft Entering to the Main Hole and the Key Points of Construction

The construction geological condition is complex in the transition section from the inclined shaft to the main hole. There are two kinds of construction schemes. After the comparison of the advantages and disadvantages of the two different construction schemes, it has selected the construction scheme of the rectangular pilot tunnel vertical to the main hole. This paper solve the construction problem of the transition section from the inclined shaft to the main hole of large cross section tunnel of passenger dedicated line under complicated geological conditions. According to the previous research results, the method can be used to large-cross section tunnel. The scaffold design and auxiliary construction measures is detailed. Compared with the expected duration, it completed the transition construction ahead of time with the speed superior to the ones of other similar works, and forming a safe and efficient construction situation.

Stability Analysis on Rectangular Transition Section Tunneling in Beiwan Horsehead Region of No. 7 Subway

The settlement of ground and vault by tunneling has important effect on construction safety and normal operation of urban transport system. The soils around reserved shaft of Beiwan region in No.1 section of Beijing Metro Line No.7 are backfilled and complex. In order to tunnel safely and keep surrounding structures safe, the stability of rectangular transition section by tunneling of Beiwan horsehead region is analyzed. Based on the data of surface survey, drilling, prediction detection of the strata and engineering design, the software of 3D FLAC is used to study the vault and ground settlements during the excavation of six pilot tunnels of rectangular transition section, and the results are also compared with the results of in-situ monitoring. The research shows that the results of numerical simulation and in-situ monitoring are matched very well, the ultimate ground settlement will be 17 mm when the transition tunnel is excavated by non-shrinkage (WSS) pre-grouting method and CRD method, and meets with the requirements of standard specification. Therefore, the six-pilot-tunneling method is good for keeping the transition tunnel stable.

Stability Analysis on Rectangular Transition Section Tunneling in Beiwan Horsehead Region of No. 7 Subway

The settlement of ground and vault by tunneling has important effect on construction safety and normal operation of urban transport system. The soils around reserved shaft of Beiwan region in No.1 section of Beijing Metro Line No.7 are backfilled and complex. In order to tunnel safely and keep surrounding structures safe, the stability of rectangular transition section by tunneling of Beiwan horsehead region is analyzed. Based on the data of surface survey, drilling, prediction detection of the strata and engineering design, the software of 3D FLAC is used to study the vault and ground settlements during the excavation of six pilot tunnels of rectangular transition section, and the results are also compared with the results of in-situ monitoring. The research shows that the results of numerical simulation and in-situ monitoring are matched very well, the ultimate ground settlement will be 17 mm when the transition tunnel is excavated by non-shrinkage (WSS) pre-grouting method and CRD method, and meets with the requirements of standard specification. Therefore, the six-pilot-tunneling method is good for keeping the transition tunnel stable.

A Top Pilot Tunnel Preconditioning Method for the Prevention of Extremely Intense Rockbursts in Deep Tunnels Excavated by TBMs

The headrace tunnels at the Jinping II Hydropower Station cross the Jinping Mountain with a maximum overburden depth of 2,525 m, where 80% of the strata along the tunnels consist of marble. A number of extremely intense rockbursts occurred during the excavation of the auxiliary tunnels and the drainage tunnel. In particular, a tunnel boring machine (TBM) was destroyed by an extremely intense rockburst in a 7.2-m-diameter drainage tunnel. Two of the four subsequent 12.4-m-diameter headrace tunnels will be excavated with larger size TBMs, where a high risk of extremely intense rockbursts exists. Herein, a top pilot tunnel preconditioning method is proposed to minimize this risk, in which a drilling and blasting method is first recommended for the top pilot tunnel excavation and support, and then the TBM excavation of the main tunnel is conducted. In order to evaluate the mechanical effectiveness of this method, numerical simulation analyses using the failure approaching index, energy release rate, and excess shear stress indices are carried out. Its construction feasibility is discussed as well. Moreover, a microseismic monitoring technique is used in the experimental tunnel section for the real-time monitoring of the microseismic activities of the rock mass in TBM excavation and for assessing the effect of the top pilot tunnel excavation in reducing the risk of rockbursts. This method is applied to two tunnel sections prone to extremely intense rockbursts and leads to a reduction in the risk of rockbursts in TBM excavation.

Analysis and Design Approach for Large Storage Caverns

AbstractThis paper presents a case study of an underground crude oil storage project. This storage site is researched with detailed field and laboratory investigations. The layout, cross section, and elevation of the caverns are analyzed and designed based on geological and geotechnical information obtained during these investigations. In this study, two-dimensional (2D) elastoplastic analysis is performed using the finite-element code Phase 2D to study the rock mass behavior caused by staged excavation of the cavern (20 m wide×30 m high). The excavation of the cavern is simulated with different stages, i.e., excavation of a pilot tunnel and subsequent side slashing followed by excavation for a pilot bench and subsequent side slashing with a total of three benches. Displacement values obtained analytically are compared with the observed displacement as the excavation progresses. Because the 2D FEM code is based on the plain strain concept, it could not take into account the effect of excavation in other d...

Research on Shallow Buried and Large-Span Tunnelling Undercrossing a Highway

WenXiang tunnel ,one of the tunnels constructed for the ZhengXi Special passenger Railway in china. In this project we have carried out a series of research on optimizing the construction method for shallow and large-span tunnels in loess condition. According to the field monitoring of ground settlement, vault settlement and primary support stress of the tunnel section before tunnelling underneath the LianHuo Highway, the result indicates that soil settlement and primary support stress can not be controlled very well, and current construction program needs to be reformed since it can not meet construction safety requirement. Our synthetical analysis comprises the optimized methods have been used in construction, such as reducing excavation area, increasing excavation steps of pilot tunnel, reserving core soil, closing invert punctually, reinforcing primary support, etc. The security and reliability also has been verified by numerial analysis sofeware FLAC3D. From feedback of field implement and monitoring result, the effect of optimized method is significant; and all of these methods ensured this tough project implemented successfully. These results derived from our research are subject to a ceritain value that could be referred for future analogous project , in terms of controlling soil settlement and protecting surrouding building facilities.

Study of rock evaluation with tunnel side wall image in TBM pilot tunnel

Study of rock evaluation with tunnel side wall image in TBM pilot tunnel

Numerical Analysis of Tunnel Excavation Method at Greatly Cross Undermine Huangzhuang Station of Beijing Subway

Combined with the geological conditions and the project features, the selection problem of pilot tunnel construction method of Huangzhuang station is solved. Directing at the commonly used method including CD method, CRD method and double side wall pilot tunnel method, FLAC3D numerical calculation method is adapted to analysis and predict the ground surface deformation and supporting structure hand features. Through analyzing the size and law of surface settlement in this section, the feasibility and differences of these methods is concluded and analyzed. And finally an example is given.

Study on Simulation and Stability Analysis of Subway Station Excavation from the Vertical Construction Well

Beijing subway Huangzhuang stations is cross-transfer station. It has a complex tunneling structure. The characteristics of the reverse construction vertical well was been thinking in the course of excavation design. The vertical well excavation and support method, horizontal wells channel excavation and support methods, the main station pilot tunnel excavation and support methods were researched to determine in detail. In order to analysis and evaluation the feasibility of excavation and getting into hole, FLAC3D numerical simulation analysis method was applied to do simulation of the vertical well, horizontal channel and the main cavern excavation. All detail construction course of these three-part were been studied. Excavation and supporting method and progress were all included. The ground surface subsidence, deformation of support structure and strengthen structure were been got. On the condition of the vertical well support structure destruction caused by the horizontal guide hole excavation and the group cave effect caused by guiding cave excavation in main station underground building, the support structure and ground soil stability were studied. The research result gave the base technical support for the project optimization design and construction security.

Thermal Behavior of EHV Gas-Insulated Lines in Brenner Pass Pilot Tunnel

The paper deals with the thermal behavior of a double-circuit gas-insulated line inside the pilot tunnel of the future high-speed railway galleries between Italy and Austria (Brenner Basis Tunnel (BBT)). Since the active power losses generated by the power transmission line may likely be about 7 MW, the thermal behavior of the BBT pilot tunnel and its ventilation requirements have been evaluated by resorting to a suitable computer model. This model is based on a “control volume” approach: a discretization of the space and time domains leads to a network of thermal capacities and resistances to be solved time after time by means of a linear algebraic system.

Rockburst characteristics and numerical simulation based on a new energy index: a case study of a tunnel at 2,500 m depth

Rockburst is one of the most difficult problems encountered in the pilot tunnels of the Jinping II hydropower station, where the rock cover is up to 2,500 m. Some typical characteristics of the rockburst events are summarized. These events indicate the intrinsic reason of rockburst is energy release. In order to understand the outburst mechanism, a new energy index, the Local Energy Release Rate (LERR), is put forward to simulate the conditions causing rockburst. By tracking the peak and trough values of elastic strain energy intensity before and after brittle failure, the LERR was developed to help understand rockburst from the viewpoint of energy release. To test its reliability, the brittle breakage of Mine-by tunnel rock in Canada and two rock bursts in the Jinping pilot tunnels were simulated. The results showed that LERR can satisfactorily predict the intensity of a rockburst and the depth of the outburst pit. Although it is not yet possible to determine thresholds at which rockbursts will occur, the study indicates the potential of LERR for evaluating rockbursts in deep underground excavations.

Tunnelling and geotechnics: new horizons

New developments in both the theory and the practice of tunnelling are covered in the lecture. The important relationship between tunnelling and geotechnics is highlighted, and recent advances in research and practice are described, drawing on model studies, theoretical developments and field measurements from case histories from around the world. Simplified plasticity models are presented that can be used by designers to assess ground movements and tunnel lining loads in complex ground conditions. The important role of pilot tunnels and in situ measurements to validate such models, drawing on a case history from Bolu, Turkey, and on other tunnelling projects, is described. Recent technical advances in earth pressure balance tunnelling are considered, illustrated by measurements from the Channel Tunnel Rail Link project, with emphasis on key factors influencing volume loss, such as face pressure, soil conditioning and effective screw conveyor operation. A recent case history in Bologna is described, in which the innovative use of directional drilling to install curved grout tubes was employed for a compensation grouting project in granular soils. Time-dependent ground movements and tunnel lining distortions occurring after tunnelling are discussed, their magnitude depending on the relative permeability of the tunnel lining and soil, the degree of anisotropy of the soil permeability, and the initial pore pressure prior to tunnelling. The effects of tunnelling-induced settlements on pipelines are considered, drawing on centrifuge tests and analytical solutions, and a new design approach is presented, taking into account the reduction of soil stiffness with increasing shear strain as a result of tunnel volume loss. The lecture concludes with a description of a distributed strain sensing technique using fibre optic technology, based on Brillouin optical time domain reflectometry (BOTDR), and its innovative application to field monitoring of a masonry tunnel subjected to new tunnel construction beneath it.

Advanced Ground Freezing at the Hallandsås Project, Sweden

AbstractAn extensive fault zone within the Hallandsås Project Sweden, a railway tunnel project in southwest of Sweden, is subject of an advanced ground freezing operation in order to facilitate TBM excavation through this section. The rock mass within the fault zone consists of a completely decomposed gneiss and amphibolite in combination with 10 to 12 bar ground water pressure. Ground freezing was carried out in 16 horizontally drilled freeze holes with a length of 100 m. Within the 10.6 m diameter final tunnel section a small 5 m diameter pilot tunnel was excavated through the frozen area. The design and execution of the freezing and excavation operations have followed the observational method. This included prediction, monitoring and follow up of all parameters associated with design of frozen ground, such as strength and creep properties, as well as design aspects on the final segmental lining installed by the TBM. By thorough project management and active design it is possible to control the involved processes and achieve a transparent methodology in predicting and executing tunnelling using the freezing method.

Considerations for Development of the Typical Cross Section for the Koralm Tunnel

AbstractThe Koralm Tunnel, located in Austria and with nearly 33 km one of the longest traffic tunnels in the world, is part of the Trans‐European railway network. The paper presents a short project overview and describes the efforts to develop an optimal cross section by questioning general standards valid for shorter tunnels and to justify innovations. Major issues which have to be considered are tunnel lining, tunnel systems, drainage systems, traction system, track superstructure and aerodynamics. A project specific issue is the implication of the existing pilot tunnels.

Effects of rock pillar width on the excavation behavior of parallel tunnels

Most of the road tunnels were designed as a twin tunnel dual-carriage system with one traffic direction in each tunnel. However, for some long road tunnels, three-parallel-tube tunnel was required to meet the needs of construction and operation. The main aim of this paper is to numerically investigate the effects of rock pillar width on the behavior of three-parallel-tube and four-parallel-tube tunnels during excavation. The results showed that the interaction effects were related not only to the geological condition and tunnel cross-section, but also the rock pillar widths. As the pillar width reduces, the interaction effects becomes more evident. When the rock pillar width was less than two and a half times the radii of the main and pilot tunnels in adverse geology section, grouting for rock mass was required to improve the stability of the tunnel. For twin-tube tunnel, if the rock pillar width near the portal section were too narrow then the central-pillar-gallery tunnel may be constructed to reduce this effect.

A study on using fish oil as an alternative fuel for conventional combustors

Combustion tests for fish oil and its blends with fuel oils were performed in a pilot tunnel furnace and two residential boilers to evaluate fish oil as an alternative fuel for conventional boilers and furnaces. Droplet evaporation tests were also conducted as a complementary study of the combustion properties. Fish oil and the blends burned readily in the facilities. The emissions were generally lower than burning the pure fuel oil except that of NO, which was higher for blends with No. 6 residual fuel oil. With better quality No. 2 fuel oil the NO emission of the blends was at the same level as that of the pure oil. Overall fish oil showed good combustion properties and significant economic and environmental benefits are expected.