Cross Passage Construction Research Articles

Numerical Analyses of the Effect of the Freezing Wall on Ground Movement in the Artificial Ground Freezing Method

The advancement of massive construction in urban subway projects contributes to the increased use of the artificial ground freezing (AGF) method in the construction of cross passages due to its reliability and environmental friendliness. However, the uplift or subsidence of the ground surface induced by the frost heave and thawing settlement of the soil can be a problem for existing buildings, and the current design method places way too much emphasis on the strength requirement of the freezing wall. In this study, FLAC3D was employed to develop a series of state-of-the-art numerical models of the construction of a typical subway cross passage by the AGF method, utilizing freezing walls with different thicknesses. The results of this study can be used to examine the ground deformation arising from the AGF method and the influence of the thickness of the freezing wall on the AGF method.

Safety and environmental impact control of cross passage construction in soft soil strata using tunnel boring machine method

The construction of cross passages using the tunnel boring machine (TBM) method represents an emerging construction technique with numerous advantages. However, owing to the scarcity of application instances, the safety control methodologies and the regulatory patterns concerning environmental impacts remain inconclusive. In this study, a cross passage excavated using the TBM method—the first of its kind in the Tianjin area—was investigated. We identified the key risk control measures for the construction and analysed the TBM operating parameters, monitored ground and building settlements, and monitored mainline tunnel deformations and mechanical responses, revealing the ground and tunnel structure deformation patterns. The following conclusions are drawn. (1) The ground surrounding the cross-passage break-out opening was stabilised by performing secondary grouting and small-range freezing, and the break-in opening was excavated using a completely enclosed steel sleeve. These measures prevented water and sand inflows during the excavation of the break-out and break-in openings in the silt and silty sand strata. (2) The torsional moment of the cutter disc was large during the break-out phase. Break-out mainline tunnel displacement monitoring data indicated that the thrust had a significant effect on the mainline tunnel during the break-out phase. (3) The TBM tunnelling caused ground loss. The ground settlement exhibited a U-shaped distribution along the cross-passage axis, with the maximum settlement being 10 mm. (4) During the break-out phase, the deformation of the break-out mainline tunnel exhibited a duck-egg-shaped distribution. The clearance convergence of the break-out mainline tunnel was within ± 4, and the clearance convergence of the break-in mainline tunnel was controlled within ± 1 mm.

Heat transfer analysis in artificial ground freezing for subway cross passage under seepage flow

Artificial ground freezing is an environmentally friendly and reliable method for ground improvement during subway cross passage construction under variable hydrological conditions. However, natural or induced seepage flow influences significantly the closure of frozen wall, as it supplies a substantial source of heat. In this study, a physical model test was conducted based on the freezing project of a subway cross passage in Beijing Subway Line 19. A series of thermistors were installed in some representative locations to measure the temperature distribution and further calculate power demand. Besides, a hydro-thermal coupling model of freezing process under seepage conditions was derived to consider the variations of physical and thermodynamic parameters of the porous media and the latent heat of ice/water phase transition. The numerical approach was validated by the experimental results. Furthermore, four crucial indicators affecting the closure time during AGF process were quantitatively evaluated. The results showed that the closure time at seepage velocities of 0, 25.6 and 51.2 m/d were respectively 60, 110 and 441 min. Nevertheless, it was impossible to form continuous frozen bodies at 76.8 m/d. Among these indicators, the seepage velocity had the greatest effect on the thickness and shape of frozen body, while seepage temperature had the least impact.

Influence of freeze tube deviation on the development of frozen wall during long cross-passage construction

This paper investigates the influence of the deviation in freeze pipe installation on the development of the frozen wall in long cross passages by numerical simulation with ANSYS software. The study case is from the artificial ground freezing project along the Fuzhou Metro Line 2 between Ziyang Station and Wuliting Station. Two freeze-pipe configurations, i.e., one with perfectly aligned pipes without any deviation from design and another with randomly distributed deviation, are included for comparison. The effect of the random deviation in the freeze pipes on frozen wall interconnection time, the thickness of the frozen wall and the development of the temperature field is explored. For the characteristic section of the numerical model at a depth of 25 m, it is found that the frozen wall interconnection time under the random deviation case and no deviation case is 24 days and 18 days, respectively. The difference in the thickness of the thinnest frozen wall segment between the random deviation and no deviation cases is the largest in the early freezing stage (up to 0.75 m), which decreases with time to 0.31 m in the late freezing stage. The effects of random deviation are more significant in the early freezing stage and diminish as the freezing time increases.

Grouting Effects of Fully Mechanized Tunneling Method for Metro Cross-Passage Construction in Soil Strata

Grouting Effects of Fully Mechanized Tunneling Method for Metro Cross-Passage Construction in Soil Strata

Centrifugal Model Test Study on the Mechanical Characteristics of Shield Tunnels Influenced by Different Types of Openings for Cross Passages

To investigate the mechanical characteristics of shield tunnels when openings are made for the construction of cross passages, a series of centrifugal model tests were conducted. The segmental features of the shield tunnel were simulated in the tests, and the influence of different types of openings, namely, rectangular opening, small circular opening, and big circular opening was compared. External earth pressures, structural deformations, dislocations, and structural stresses were monitored during the tests, while the influence of different buried depths was also investigated. The results show that (1) soil arching effect occurred in the overlying soil due to the deformation of the tunnel, and the earth pressure reduction coefficients can guide the tunnel structural design; (2) vertical deformations of the main tunnel and the dislocations between adjacent rings increased with the opening sizes significantly; (3) significant stress concentration occurred close to the openings, and the compressive stress at the inner surface may even exceed the limit strength of the concrete. In summary, the adverse responses of the tunnel increased with the increase of the buried depth and the opening size. Targeted measures should be taken, such as temporary support, longitudinal connections, and high-strength materials near the openings.

Construction of the Tuen Mun–Chek Lap Kok Link Sub-sea Tunnels in Hong Kong

The entire Tuen Mun–Chek Lap Kok Link (TM-CLKL) was commissioned on 27 December 2020 and comprises a 9 km dual twolane carriageway between Tuen Mun and North Lantau, Hong Kong. The challenges for the construction of the TM-CLKL tunnels included sub-sea tunnelling up to 55 m below sea level in mixed ground geology that required replacement of tunnel boring machine (TBM) cutting tools at hyperbaric pressure up to 5.8 bars; replacement of worn TBM cutting tools in complicated ground conditions; construction of approach tunnels in newly reclaimed land subject to long-term consolidation; and construction of cross passages at 100-metre intervals between the two sub-sea tunnels with a risk of sea water ingress at 5.5 bars. This project has deployed sophisticated techniques to surmount the challenges encountered during construction of the five-kilometre-long sub-sea tunnels. These included the use of the world’s largest slurry-type Mixshield TBM, 17.63 m in diameter, for the construction of the northern approach tunnel, followed by two 14 m diameter slurry-type Mixshield TBMs for the construction of the sub-sea tunnels; use of saturation diving techniques for TBM cutterhead interventions up to 5.8 bars which was the first such works in Hong Kong and one of only a few uses of saturation diving in tunnelling worldwide; use of ground freezing techniques in complicated ground conditions for TBM interventions to change worn cutting tools at the TBM cutterhead; TBM tunnelling in newly reclaimed land at the northern landfall and the southern landfall; and the construction of cross passages by mini-TBM using pipe jacking methods between the two main tunnel tubes which was the first such works ever undertaken anywhere in the world. This paper introduces the successful implementation of these techniques for the satisfactory completion of the TM-CLKL sub-sea tunnels.

A Case Study of Constraint Cross-Passage Construction in Urban Tunneling

Abstract: The paper aimed at a detailed case study of cross-passage, which is forced to design and construct by connecting the station box and main tube tunnel of Marol Naka station in Mumbai Metro Line 3, since the marol Naka is densely populated area and elevated metro line is passing over an underground station, therefore further excavation of tunnel is done through the cross-passage. In these station, the cross- passage is constructed for public utilities for connecting the station box to the platform and also for the emergency exit. During tunnel construction, the cross passage is excavated after the main tunnel has been constructed. At the same time, the safety of the cross passage and the stability of the tunnel must be ensured by instrumentation and monitoring. Design of the cross- passage is achieved according to the principles of “New Austrian Tunnelling Method’ (NATM) and the composite lining structure is adopted. NATM is used to widen the station platform which is initially tunnelled by the TBM. The dimension of 230m long and 15m wide Marol Naka station has 16 cross-passages which are constructed connecting the station box to the platform; the observations and the designing part- Finite Element method is used in order to evaluate stress deformations induced on the cross-passage. Keywords: Cross passage, NATM, TBM, Finite element method, Marol Naka station, Emergency exit.

Refined Calculation of Temperature Field in Cross-passage by Artificial Ground Freezing

In China, the artificial ground freezing (AGF) method is widely used in the construction of cross-passages, however, it is difficult to accurately calculate the numerical solution of the freezing temperature field. In this paper, the boundary conditions in the numerical calculation are refined through in-suit measurements, and finally the freezing process of the connecting channel is effectively simulated. The calculation results show that the thickness and temperature of the frozen wall at 1.0 m near the main tunnel segment are significantly weakened. The frozen wall at the top of the cross-passage is affected by densely arranged holes, which is prone to excessive freezing. And based on the calculation results, an optimization plan for the highest cooling efficiency in the initial stage of active freezing and speeding up freezing is proposed.

Use of artificial ground freezing in construction of cross passages under Suez Canal

AbstractThe Artificial Ground Freezing (AGF) has demonstrated its versatility as an effective approach for both temporary ground stabilization and ground water control in almost all types of saturated soils. This paper describes the use of a closed circuit freezing system in the construction of four cross passages. The passages connect 4.8 km long twin road tunnels that have recently been constructed at depths of up to 60 m under Suez Canal in Ismailia, Egypt. The paper starts by describing the ground conditions at the locations of the cross passages and by presenting the results of laboratory tests conducted on unfrozen, frozen and thawed soil specimens. The main design criteria considered in designing the freezing works are discussed and the freezing and cross passages construction works are described. The frozen body was carefully monitored during the freezing process and construction of passages. Records of the adopted monitoring program are presented and discussed. Significant observations that contribute to effective planning of future freezing works are also presented.

Optimization of deep soil mixing mass for construction of tunnel cross-passage in Bangkok

A cross-passage from a tunnel to an intervention shaft in Bangkok subsoils was modelled using three-dimensional finite element analysis. The optimization was performed for reducing the volume of soil-cement mass while maintaining ground stability. The result showed that the factor of safety increases linearly with the thickness of improved ground. The relationship between the improved groundmass and ground surface settlement curve was made. It was found that the predicted settlement profile can be captured by the formula proposed by Peck and O’Reilly, providing that the empirical coefficient of 0.6 is fit well with the results from the 3D simulation. This value was obtained from the average of empirical coefficient value 0.4 and 0.7, which are the empirical coefficient values of stiff clay and soft clay, respectively based on the overburden thickness.

Research on the Ground Subsidence Mechanism of Cross Passage Caused by Freezing Method Construction

At present, the built or newly built underground structures are mostly concentrated in developed areas along the coast, lakes, and rivers, while deep soft soil is widely distributed in these areas. The cold heat treatment method is one of the advanced foundation treatments and has broad application prospect. However, geothermal exchange and temperature field change are complex Stefan problems with mobile boundaries, internal heat sources, and phase changes. It is important to determine the freezing area and freezing temperature reasonably under the premise of ensuring the safety of the frozen construction. Therefore, this paper summarizes the research methods of freezing method construction of cross passage and introduces the research on the constitutive model of freezing undisturbed soil, the theory of freezing wall calculation, and the evolution mechanism of the temperature field. Then, a brief evaluation is made in view of the lack of research, and the development direction of this field is put forward with the research characteristics. It is to deepen the understanding of the deformation mechanism of cross passage embedded in soft soil caused by the freezing and melting.

Research on Stress Characteristics of Segment Structure during the Construction of the Large-Diameter Shield Tunnel and Cross-Passage

With the intensive development of China’s high-speed railway network and intercity railway network, the construction of the large-diameter shield tunnels and cross-passages is gradually increasing. The construction of large diameter shield tunnels and the excavation of cross-passages puts forward higher requirements for the stability and safety of segment structure. Based on the Wangjing tunnel project, this paper studies the segment displacement and mechanical response of the shield tunnel with a diameter of 10.5 m in the process of shield construction and cross-passage construction. The results show that during the construction of large diameter shield tunnels, the vault and invert produce inward displacement, the invert uplift usually is more severe than the vault settlement, and the arch waist on both sides produces outward displacement. Near the segment K (capping block), the mechanical performance of the segment is close to that of the hinge or chain rod, which can only effectively transmit the axial force but cannot resist the bending moment and shear force. During construction of the cross-passage, the maximum deformation and stress of shield tunnel segment are symmetrically located at the interface of the main tunnel and cross-passage. The upper and lower edges of the segment at the interface tend to change from compression to tension. At the same time, the steel bars on the inside and outside of the segment vault and the arch waist change from compressive stress to tensile stress, which can easily lead to segment damage, so these positions can be reinforced by erecting section steel frames before construction.

Thermal Behavior in Cross-Passage Construction during Artificial Ground Freezing: Case of Harbin Metro Line

The successful construction of cross passages in water-rich sand strata requires the ground reinforcement of soil in passage zones. To address these conditions, artificial ground freezing was introduced, which is an innovative presupport technique that has been extensively applied in tunnel engineering. However, insufficient temperature monitoring data and complex numerical models have hindered accurate predictions of complete freezing curtains in engineering applications. In light of this, this paper proposes a heat–moisture coupling model to predict the dynamic formation of the freezing curtain. This was achieved by combining the heat transfer, Richards’s equation, and the Darcy equation for porous media. As a result, the hydraulic parameters could be obtained through nuclear magnetic resonance. The proposed numerical model was further validated through laboratory testing by applying various seepage flow conditions. Finally, a three-dimensional numerical model was established for the construction of cross passage during artificial freezing. To confirm the feasibility of the model, data from 53 points were continuously collected from the case study for more than 50 days. The proposed model delivers temperature results that are consistent with the field data.

In situ monitoring of temperature and deformation fields of a tunnel cross passage in Changzhou Metro constructed by AGF

Artificial ground freezing (AGF) technology characterized by good waterproof performance, wide adaptability, minimal pollution, and other advantages has been widely used in the construction of tunnel cross passages buried in the soft soil layers. Based on the in situ monitoring, the temperature field of the freezing wall and the deformation field around a cross passage are studied in this paper. The results show that the descent speed of the soil temperature is large at the beginning and becomes small gradually, and finally tends to be stable. The frozen cylinders are enclosing in the phase transformation stage of water. The closer to the freezing pipes the soil is, the faster the soil temperature drops. The temperature of the soil inside the freezing wall is lower than that of the soil outside the freezing wall. The frost heave capacity at the center of the cross passage is the largest, so is the growth rate of the frost heave. The results can offer a reference to the design and construction of the cross passages buried in the soft soil areas.

Pore Size Changes in Marine Soft Soil under Various Freezing Conditions

Artificial freezing methods can help highlight the mechanical properties of marine clay. The construction of cross passages in metro tunnels employs the freezing method. Freeze–thaw circulation, which is part of the process, affects the engineering properties of clay and produces differential settling. This paper describes the percentages of specific diameters of frozen–thawed soil under different freezing temperatures, measured with the help of nuclear magnetic resonance (NMR). In response to the experimental results, a weakening effect of freezing temperature and speed on soft soil is proposed. All sizes of undisturbed soil pores tend to increase under various freezing temperatures. Owing to differences in free water content, the water in medium pores freezes quicker than that in tiny pores. The quicker the freezing, the greater the resulting void ratio. Finally, potential reasons for changes in pore size under different freezing conditions are explained from a microcosmic perspective.

Study on the Mechanism of Grouting Under Different Tunnel Depth of Cross Passage

Based on a cross passage construction project, numerical simulation and analysis were carried out, which revealed the mechanism of grouting in the construction of the subway cross passage. The effects of different grouting properties, different grouting range and tunnel depth on the reinforcement were studied. According to different tunnel depth, the properties and range of grouting were determined. The characteristics of surface settlement, lining force, stress and plastic zone distribution after cross passage construction were compared. The result shows that: (1) In the case of the above geological properties, for a tunnel with a depth of 9 m (1.5 D), the grouting property is fair and the grouting range is 2 m can prevent the occurrence of failure. (2) Due to the higher stress, larger tunnel depth needs to increase grouting range to prevent the occurrence of failure. This research can provide some reference and guidance for similar projects.

Field Test Study of the Artificial Ground‐Freezing Method Subsurface Excavation Construction of Watered Sandy Stratum in Collapsible Loess Area

Saturated sandy stratum often makes tunnel excavation exceedingly difficult owing to its high water content. The artificial ground‐freezing (AGF) method is an effective way to reduce the construction risks in such stratum; however, the AGF mechanism in the saturated sandy stratum of a collapsible loess area still lacks sufficient research. Based on field tests and numerical simulations, this study investigates the regularity of the temperature development, frost heave, and thaw subsidence distribution during the cross passage construction of a saturated sandy stratum in a collapsible loess area, using the AGF method. The results showed that the inward development rate of the frozen soil wall in the saturated sandy stratum was faster than its outward development rate. The gradient of the soil cooling curve was positively related to the longitudinal depth of the cross passage. The thickness of the frozen soil wall calculated by the slowest development rate of the frozen soil was conservative. The application of the pressure relief hole was beneficial to the release of the frost‐heaving force and the control of the frost‐heaving displacement. The pressure gauge pressure increase could be used as an identifier for the closure of a frozen soil wall. After excavation, the inner wall of the cross passage moved toward the inner space of the passage.

High Water Ingress during TBM Tunnelling under Andheri Kurla Road, Marol Naka, Mumbai, India.

For surface space limitations in metro cities, tunnel is the best option worldwide for the development of modern transport system, utilities and other infrastructures. But tunnelling is full of surprises depending on geological and hydrological factors. Underground Mumbai Metro line -03 is also full of surprises. In this paper we are going to discuss the encountered high water pressure during the Up line mining underneath the Andheri – Kurla road & elevated Mumbai Metro line -01 at Marol Naka. Pressure of water was observed to be 4.5 bars to 5 bars, geotechnical instruments showing no settlement but tunnel always filled with muck and progress were affected badly apart from taking precautions during the mining. As per geology, grade III basal and breccia were encountered. Team tried to find out the source/causes of this high water ingress but even after searching various options such as utility damage, recharging with water body, geological & geophysical investigation options, it was unable to conclude the confirm source. It was very astounding that no high water ingress was observed during the down line TBM mining. In this paper, all options have been discussed in details and also suggesting for taking high precautions during construction of cross passage in this area.

High Water Ingress during TBM Tunnelling under Andheri Kurla Road, Marol Naka, Mumbai, India.

For surface space limitations in metro cities, tunnel is the best option worldwide for the development of modern transport system, utilities and other infrastructures. But tunnelling is full of surprises depending on geological and hydrological factors. Underground Mumbai Metro line -03 is also full of surprises. In this paper we are going to discuss the encountered high water pressure during the Up line mining underneath the Andheri – Kurla road & elevated Mumbai Metro line -01 at Marol Naka. Pressure of water was observed to be 4.5 bars to 5 bars, geotechnical instruments showing no settlement but tunnel always filled with muck and progress were affected badly apart from taking precautions during the mining. As per geology, grade III basal and breccia were encountered. Team tried to find out the source/causes of this high water ingress but even after searching various options such as utility damage, recharging with water body, geological & geophysical investigation options, it was unable to conclude the confirm source. It was very astounding that no high water ingress was observed during the down line TBM mining. In this paper, all options have been discussed in details and also suggesting for taking high precautions during construction of cross passage in this area.