Middle Partition Research Articles

Numerical Simulation Study of the Vibrational Response of Continuous Arch Tunnels under the Action of Overlying Train Loads

With the rapid development of transportation infrastructure in China, continuous arch tunnels passing under existing operational railways are increasingly encountered. This paper primarily investigates the mechanical response patterns of the lining of continuous arch tunnels under the vibrational loads generated by trains traveling on railways. To this end, a three-dimensional finite element model of the dynamic response of continuous arch tunnels under train vibrational loads was constructed using Midas GTS/NX software. This model explores the patterns of acceleration, dynamic displacement, and dynamic strain responses of continuous arch tunnels under the action of moving train loads. The study reveals that under train vibrational loads, the vertical acceleration, vertical displacement, and strain time history curves at various monitoring points in the continuous arch tunnel exhibit vibrational characteristics. The acceleration, vertical displacement, and dynamic strain increase as the train enters, fluctuate within a certain range, and then decrease to zero as the train exits. Under high-speed train loads, the acceleration peak values at the arch feet and outer sidewalls of the left and right tunnels are larger, with a greater peak value difference. The vertical displacement peak values at the arch shoulders and crown are larger, whereas those at the middle partition wall and base slab are smaller. During the process from the train's entry to its exit, the dynamic strain exhibits a trend of initially increasing, then stabilizing, and finally decreasing to zero, all while displaying vibrational characteristics. The strain response on the tunnel side where the train enters is greater than that on the side where it exits.

Regular and chaotic dynamics in a 2D discontinuous financial market model with heterogeneous traders

We develop a financial market model where three types of traders operate simultaneously: fundamentalists and chartists of two types, namely, trend followers and contrarians. The dynamics of this model is described by a two-dimensional discontinuous map defined by two linear functions, where one acts in the partition between two (parallel) discontinuity lines and the other one acts outside this partition. Our analysis shows that despite the linearity of the map components, its dynamics can be quite complex, with various, possibly coexisting attracting cycles and chaotic attractors. As a first step towards the understanding how the overall bifurcation structure observed in the parameter space of the map is organized, we obtain analytically the boundaries of periodicity regions related to the simplest attracting period-n cycles, n≥3, with one point in the middle partition and n−1 points outside it. These boundaries can be related to border-collision bifurcations (when a point of the cycle collides with a discontinuity line) as well as to degenerate bifurcations (associated with eigenvalues on the unit circle). We show also some elements of period-adding and period-incrementing bifurcation structures for which the cycles mentioned above are basic. From an economic point of view, our study confirms that a fairly simple financial market model with heterogeneous agents is able to produce complicated boom-bust dynamics typical of real financial markets.

Cracking Characteristics and Mechanism of Internal Components of Large-Span Shield Tunnel

With the ever-increasing number of large-span shield tunneling projects and the extended operational time, their distinctive internal component issues are becoming more pronounced and exhibiting unique characteristics. In order to reveal the cracking mechanism of concrete on the top of the middle partition wall, based on a large-span shield tunnel section of Nanjing Metro, the crack mode, distribution characteristics, and cracking process of concrete inside tunnel structure were studied by combined field investigation and extended finite element analysis. The results showed that: (1) there were 96 cracks of concrete on the top of the middle partition wall in the interval. Based on the propagation path, number, and shape of cracks, they could be divided into type I, II, III, Y, and Z, with type-Y and type-Z being subtypes of type-I. (2) The crack started at the opposite side of horizontal differential displacement of the flue plate. The development curves of the length and end width of type-I and type-II cracks showed the significant characteristics of three stages. The relationship between crack end width and length was nonlinear, showing that 250 and 225 mm, respectively, were the critical crack lengths growing with the rapid growth of the end width of type-I and type-II cracks. (3) In type-II cracks, the propagation curves of two cracks under the same working condition were consistent, and the spacing of plate joints greatly influenced the length and slope of each stage of the curve. For type-III cracks, the first crack propagation process was basically consistent with type-I and type-II cracks, and the propagation of the other two cracks had obvious brittle characteristics.

Influence of the door opening on the pressure transient caused by the high-speed subway train passing through the double-track tunnel with the mid-partition wall

Double track tunnel with mid-partition wall is a widely used subway tunnel. In such tunnels, in order to avoid the fire door on the middle partition wall from invading the gauge, the fire door is often removed to form door openings. The existence of door opening connects two parallel tunnels, which affects the aerodynamic effect caused by high-speed subway train passing through the tunnel. In this study, a double track tunnel with mid-partition wall was taken as an example to analyze the aerodynamic effect of high-speed subway train under the door opening conditions, moreover, the surface pressure of two adjacent tunnels and train surface pressure was also analyzed. In addition, the propagation mechanism of pressure wave in open door tunnel was analyzed in detail, and the superposition law of branch pressure wave caused by open door was pointed out. The results indicated that the presence of door openings is beneficial for controlling the peak pressure on the tunnel surface and train surface. For a door opening with a cross-sectional area of 5 m2 (cross-sectional area ratio of 0.116), when the door opening is located 300 m and 700 m away from the tunnel entrance, the peak positive pressure can be reduced by up to 21.9 % and the peak negative pressure can be reduced by 21.1 %. The cross-sectional area and number of door openings have a limited effect on reducing the peak pressure of the tunnel. Compared to the number of door openings, the position of the door opening has a more significant impact on the peak pressure inside the tunnel and on the surface of the train.

Investigation of cracking mechanism of the first tunnel lining during double-arch tunnel construction

To solve the engineering problem of the first tunnel lining cracking caused by the second tunnel construction of double-arch highway tunnels, a research method combining distributed optical-fibre monitoring, inversion analysis and numerical simulation that can reflect lining cracking was presented. Optical fibres were laid on opposite sides of the steel arches inside the first tunnel lining. Embedded optical-fibre monitoring was conducted continuously during the second tunnel driving. Based on the fibre-optic strain profile, the lining cracking was deduced and warned in time. The mechanical behaviour of the steel arch was investigated by the inversion analysis, which took into consideration the integrated impact of axial force and flexural moment. A two-dimensional (2D) load-structure method–based numerical model was established, considering the influence of different load distributions in each construction condition. The total strain rotating crack constitutive model was applied to reflect the cracking behaviour of concrete lining in the simulation, and the model was calibrated and verified in the laboratory. Comparative analysis between the simulated strain distribution and the distributed optical-fibre monitoring results was carried out. The deformation mode and crack distribution of the lining were analysed. The cracking mechanism was explained. Specifically, the second tunnel construction led to the loading at the top of the middle partition wall and the release of rock pressure in the first tunnel. Under these load changes, the secondary lining of the first tunnel cracked on the inner side of the top of the middle partition wall owing to tension, and compression-bending failure occurred near the right arch foot. Finally, the influence of the parameters on the lining force was analysed, and a construction optimisation scheme was proposed.

Research on Construction Sequences and Construction Methods of the Small Clear-Distance, Double-Arch Tunnel under an Asymmetrical Load

A small clear-distance, double-arch tunnel under an asymmetrical load combines the characteristics of small clear-distance, tunnels and double-arch tunnels, and the influence of an asymmetrical terrain must be considered. Its construction stability is a problem worth studying. This paper used the Wengcun tunnel as the engineering background. Midas/GTS finite element analysis software was used to study the effects of eight excavation sequences and two excavation methods on tunnel stability. The results showed that the deformation and force of the tunnel were asymmetric under the asymmetrical terrain. Both middle partition walls were deformed towards the shallowly buried side, and the shallowly buried side was deformed to a greater extent. Excavating shallow side tunnels first can effectively mitigate the impact of asymmetric terrain. The arch settlement of the Center Diaphragm Excavation Method is 1.33 cm, which is smaller than the three-step excavation method of 1.48 cm; however, this difference is not significant. The Three-bench Excavation Method was more efficient. Based on the conclusion of a numerical simulation, the construction site adopted the construction sequence of excavating the shallowly buried side tunnel first and adjusted the excavation method to the Three-bench Excavation Method.

The Change in Dynamic Response Distribution of Double-Track Tunnel Structure Caused by Adding Middle Partition Wall

Adding a middle partition wall is an effective method to prevent the interaction between the upper and lower subway lines in a double-track tunnel, and the subsequent change in the dynamic response of the tunnel structure caused by adding a middle partition wall has drawn attention. We analyzed the displacement and acceleration responses of the upper part (zone A), the lower part (zone B), the tunnel bed and the surrounding connecting part (zone C) of the double-track tunnel by establishing a two-dimensional finite element model of the double-track tunnel and soil with and without a middle partition wall. The numerical results demonstrate that the addition of the middle partition wall improves the displacement and acceleration response distribution of the double-track tunnel structure. Compared with single-train traffic, the addition of the middle partition wall brings more obvious changes to the dynamic response of the double-track tunnel during double-train traffic. The maximum displacement response decreases from 5.881 mm to 5.335 mm, and the maximum acceleration response decreases from 18.51 m/s2 to 16.62 m/s2. The displacement response value in the upper part increases from 1.0 mm to 1.5 mm, the acceleration response value increases from 3.0 m/s2 to 4.6 m/s2, the displacement response value in the tunnel bed and the surrounding connecting part decreases from 5.0 mm to 3.0 mm, and the acceleration response value in the tunnel bed and the surrounding connecting part decreases from 18.0 m/s2 to 10.0 m/s2. There is no obvious change in the lower part. During double-train traffic, after adding the middle partition wall, the horizontal displacement and horizontal acceleration response values of the double-track tunnel structure decrease by about 30% to 45%; the vertical displacement response value of the connection between the middle partition wall and the lining increases from 1.337 mm to 1.774 mm, an increase of 32.7%, and the vertical acceleration of the lower half of the tunnel lining is partially transferred to the upper half. The response values of horizontal displacement and acceleration in the middle part of the middle partition wall are the largest, at 1.6 mm and 6.0 m/s2, while the response values of vertical displacement and acceleration in the bottom of the partition wall are the largest, at 3.3 mm and 9.0 m/s2. The research results provide a reference for the structural design of middle partition walls to ensure the safety and stability of trains running in double-track tunnels.

Numerical Simulation of Ultra-Shallow Buried Large-Span Double-Arch Tunnel Excavated under an Expressway

The temporal and spatial effects of a complicated excavation process are vital for an ultra-shallow buried large-span double-arch tunnel excavated under an expressway in service. Numerical simulations are urgent and necessary to understand the effect of the total construction process. Taking Xiamen Haicang tunnel as a research object, the total excavation process of three pilot tunnels and the three-bench reserved core soil method of an ultra-shallow buried large-span double-arch tunnel with a fault fracture zone under an expressway was simulated using software FLAC3D. The deformation of the surface, surrounding rock, underground pipelines, tunnel support structure and partition wall of the three pilot tunnels and the main tunnel was analyzed, and the dangerous areas and time nodes were obtained. When the tunnel was excavated to the fault fracture zone, the deformation of the surface and surrounding rock increased significantly. The rock and soil within 20 m behind the excavation surface of the pilot tunnel were greatly disturbed by the excavation. During the excavation of the main tunnel, the horizontal displacement of the middle partition wall moved slightly towards the main tunnel excavated first. The research results can provide a reference for the construction design of double-arch tunnels.

Evaluation on the solketal production processes: Rigorous design, optimization, environmental analysis, and control

This works aims at evaluating different process configurations for producing solketal from reacting glycerol with acetone. The research carries out the regression of thermodynamic and kinetic parameters, rigorous design of four process configurations, optimization, carbon emission analysis, and control. The results from steady-state analysis reveal that the solvent-free coupled reaction/distillation (SFCRD) process is the most promising. It reduces 40.09% of total annual cost and 45.09% of CO2 emission from the base case, the separated reactor-distillation process. Besides, the CO2 emission rate of the SFCRD process is found 35.29% and 65.91% less than the recently reported upper and the middle partition reactive dividing-wall column process, respectively, indicating the unfavorability of intensifying this reacting system through reactive distillation. Finally, a control structure for the SFCRD process is established for effectively handling the disturbances from the flowrate, composition and catalyst deactivation. Through the dynamic simulation, the closed-loop control results were revealed satisfactory.

Analysis of mechanical behavior of primary lining in double-arch tunnel based on distributed fibre optic monitoring

Cracking and crushing were observed in the first tunnel lining of the Kaidagu double-arch tunnel (China), excavated in weathered surrounding rock. This concrete damage occurred during excavation of the second tunnel. It was necessary to monitor the continuous strain distribution along the entire cross section of the lining. Optical fibres were attached to the inner and outer surfaces of the steel arch (primary lining) of the first lining, and monitoring was carried out during the second tunnel excavation. The overall strain distribution was obtained by the fibre optic monitoring, and the internal force and external load distribution of the primary lining were calculated using the proposed inversion analysis method. The calculation results indicated that the axial compression between the right arch shoulder and the right arch foot decreased, which could cause the internal forces of the middle partition wall to increase. The damage mechanism of the lining was inferred. For the first time, optical fibres were installed inside the lining instead of on the inner surface, and the inverse analysis method, which considered the combined effect of axial force and bending moment, was applied to the mechanical analysis of the primary lining. The calculations and analyses provided valuable information for the design and construction of similar projects.

Application of Glass Fiber Concrete under Thin-Walled Middle Partition Wall Construction in Tunnel

Aiming at the feasibility of applying glass fiber concrete as a new material to tunnel engineering, with the help of a combination of theoretical analysis, laboratory tests and engineering applications, the effect of glass fiber on the mechanical properties of concrete under different dosages and different lengths is studied. By monitoring the cracks in the middle partition wall, and applying the glass fiber to the middle partition wall in Laoshan Tunnel, to achieve the verification of the optimal length and the optimal mixing amount. The main conclusions are: (1) When the length of glass fiber is 12 mm, the tensile and compressive strength reach the maximum value; (2) Determine the optimal volume rate is 1% in order to prevent the concrete cracking effectively; (3) The crack resistance of the mid-board with glass fiber concrete is better than the ordinary concrete, which proves the feasibility of practical application of glass fiber concrete.

Research on Construction Control Technology of Large-Span and Small Clear Distance Underpass High-Voltage Line Tunnel

Hanping tunnel is a control project of national highway 310 Dahejia to Qingshui highway project. It needs to cross a 330kV high-voltage transmission line under the condition of small clear distance, which requires high construction requirements. In view of the difficulties such as shallow buried depth of tunnel and small clear distance between tunnel and tower of high-voltage line, multiple excavation blasting method is adopted, and smooth blasting, charge quantity control and damping hole setting are comprehensively used to reduce the impact on the tower and structure of high-voltage line. In order to ensure the smooth progress of the project, the large-scale finite element analysis software is used to simulate the whole excavation project. The influence of the full-section method and the middle partition wall method (CD method) on the surrounding rock and the high-voltage electric tower is compared. It is found that the CD method can effectively control the displacement of the surrounding rock and the tower on it and the uneven settlement.

Optimization of Construction Parameters and Deformation Characteristics of Large-Section Loess Tunnel: A Case Study from Xi’an Metro

Loess geological tunnels are characterized by weak geological structure and poor self-stability of surrounding rock, so effectively controlling the excavation face distances of different caverns is of great significance for guiding the safe construction of large-section tunnels. Based on the excavation of large-section loess tunnel from Xi’an Metro Line 4, the optimal excavation face distance is determined based on Midas numerical model. Then, the surface settlement and horizontal deformation are analyzed based on monitoring data, and, finally, the rationality of excavation face distance is verified. The results show that the influence of excavation face distance on surface settlement, vault settlement, and horizontal deformation is consistent. The surface settlement mainly occurs in the range of −20∼20 m from the tunnel centerline and the settlement trough formed has asymmetric characteristics. The vault settlement and horizontal deformation undergo first a rapid settlement and then a slow settlement. The connection between initial support and middle partition is mainly tensile stress and the middle and bottom parts of the supporting structure are mainly compressive stress. Numerical results suggest that the optimal excavation faces distance of L1, L2, and L3 which can be 4, 9, and 9 m, respectively. Construction monitoring data show that the double-sides heading method has a significant effect on surface settlement, vault settlement, and horizontal deformation. The surface settlement occurs within the range of −17∼6 m from the tunnel centerline. The maximum vault settlement and horizontal deformation are 73.00% and 65.50% of the maximum allowable. It can be seen that the actual excavation parameters optimized by Midas numerical model have high reliability.

Shoulder scaption is dependent on the behavior of the different partitions of the infraspinatus muscle

PurposeThe purpose of this study was to investigate if the three partitions (superior, middle, and inferior partitions) of the infraspinatus muscle previously described in anatomical studies will present different behavior during scapular plane abduction (scaption) as described using shear-wave elastography, especially during initial range of motion.MethodsEight volunteers held their arm against gravity 15° intervals from 30° to 150° in scaption. Shear-wave elastography was implemented at each position to measure shear modulus at rest and during muscle contraction, as a surrogate for muscle stiffness, of each partition. Muscle activity was defined as the difference in stiffness values between the resting positions and those during muscle contraction (ΔE = stiffness at contraction—stiffness at rest).ResultsThe activity value for the middle partition was 25.1 ± 10.8 kPa at 30° and increased up to 105° (52.2 ± 10.8 kPa), with a subsequent decrease at larger angle positions (p < .001). The superior partition showed a flatter and constant behavior with smaller activity values except at higher angles (p < .001). Peak activity values for the superior partition were observed at 135° (23.0 ± 12.0 kPa). Increase activity for inferior partition began at 60° and showed a peak at 135° (p < .001; 32.9 ± 13.8 kPa).ConclusionStiffness measured using shear-wave elastography in each partition of the infraspinatus muscle demonstrated different behavior between these partitions during scaption. The middle partition generated force throughout scaption, while the superior and inferior partitions exerted force at end range.

Transport-related stress in five-day-old foals and their dams

Horses are frequently transported by road but little is known about the stress response of transported newborn foals. In this study, we have analyzed the stress response of postpartum Haflinger mares (n = 6 over two years) and their 5-day-old foals (n = 12) to a 20 km road transport in a trailer with the middle partition either removed or separating the mare and her foal. Noninvasive techniques were used to analyze the physiological stress variables such as salivary cortisol, heart rate, and heart rate variability (HRV). Mares and their foals responded to transport with an increase in cortisol concentration (P < 0.001). The increase was more pronounced and prolonged in foals compared to their mothers (P = 0.001). Heart rate increased in mares and foals during transport (P < 0.001) but this increase was less pronounced in foals compared to mares (P = 0.001). The HRV increased during transport (P < 0.05) in mares but remained constant in transported foals. The presence or absence of the partition was largely without effect on the physiological stress variables determined. In conclusion, 5-day-old foals respond to road transport with a clear adrenocortical activation which was more pronounced than in their dams. There were no changes of HRV in transported foals.

Effective Control of Vapor Recompression-Assisted Dividing Wall Column with a Middle Partition

Vapor recompression-assisted dividing wall columns (VRC-DWCs) with a middle partition have been shown to have a higher energy efficiency compared to conventional DWCs. However, the controllability ...

Analysis on Deformation Control Technology for Large-Span Subway Tunnels from High-Narrow Channel

The construction process of the transverse channel to the large-span tunnel is complicated, the mechanics change frequently, and the construction safety risk is high. Relying on the Huangshan Street Station project of Wulumuqi subway tunnel, combined with the key technology in the construction of the transverse channel to the large-span tunnel, this paper aims to analysis the deformation during the construction of subway tunnel from transverse channel by numerical simulation method. The results demonstrate that the the bearing system of “frame beam plus middle diaphragm” is adopted in the construction of the main tunnel with large cross-section, and the deformation can be effectively controlled by “double-layer support structure” in the sand gravel layer. Therefore, the surface settlement has passed through three stages of “rapid growth—slow growth—stable”, and the maximum value of 13.32mm, which ensures the construction safety in the breaking process of transverse channel. Moreover, when the temporary middle partition wall is removed, the displacement of the measuring point will be greatly deformed during the construction of the positive hole. So the length of the support removed should be shortened, no more than 6m and on-site monitoring should be strengthened in this process.

Large‐Scale Shaking Table Test of Seismic Response Laws for a Shallow Double‐Arch Tunnel under Unsymmetrical Pressure with a Damping Layer

Based on the similarity theory, a large‐scale shaking table test of a shallow double‐arch tunnel under unsymmetrical pressure with a similarity ratio of 1 : 20 was designed and completed, and a foam concrete damping layer was set in the double‐arch tunnel. The acceleration response, strain response, and crack distribution of double‐arch tunnels under different intensities and different directions of the Wenchuan wave excitation were studied (WC‐X, WC‐Z, and WC‐XZ). The results showed that (1) the bias side (right hole) is greatly affected by the unevenness of the cover soil, and the horizontal acceleration response difference between the two tunnels is large and there is no symmetry. The incident direction of seismic waves has a great influence on the acceleration response of double‐arch tunnels. The amplification factor of WC‐Z is greater than that of WC‐X. (2) On the same horizontal plane, with the vertical centerline of the middle wall as the axis of symmetry, the vertical acceleration amplification factor also has a large difference between the arch foot and the shoulder, but the difference is relatively small at other points. (3) The dynamic strain increases with the increase of seismic intensity, and the tendency is similar under the three different seismic wave excitation directions. The lining is under tensile strain and compressive strain, the strain of the left hole is greater than the strain of the right hole, and severe stress concentration occurs at the top left of the mid partition. (4) The middle partition, shoulder, and vault of the left hole and the shoulder, vault, and foot of the right hole are weak parts of earthquake resistance. Therefore, special attention should be paid to the seismic design.

Optimization of construction parameters of Highway Tunnel CRD Method

For shallow buried tunnels with poor surrounding rock stability, reasonable construction parameters are of great significance for ensuring tunnel construction safety and controlling construction quality. Taking Huiqing a tunnel as an example, comprehensive analysis of the partition wall R=11.6 ∠ 520, R=5.76 ∠1060, R=5.46 ∠1040, R=+∞∠1800 three different radii of curvature, using FLAC software for four calculations Numerical simulation of working conditions, analysis of plastic zone changes and surrounding rock deformation under different calculation conditions, and the radius of curvature of this project is proposed. The research results show that the middle partition wall adopts R=5.76 and the central angle=1060 can ensure the stability of surrounding rock and the minimum deformation of surrounding rock, which can provide a certain reference for the construction of such highway tunnels.

Force and Deformation Characteristics during the Reconstruction and Expansion of Shallow Single-Tube Tunnels into Large-Span Multiarch Tunnels

At present, there are an ever-increasing number of tunnel expansion projects in China. Studying the mechanical properties of the expanded tunnels is of great significance for guiding their safe construction. Through model testing and numerical simulation, the mechanical properties of a double-arch tunnel constructed through the expansion of the middle pilot heading from an existing single-tube tunnel were studied. The variation characteristics of the surface subsidence, surrounding rock stress, and stress and strain of the middle partition wall and lining during the tunnel reconstruction and expansion were investigated. The mechanism for transferring stress and strain between the left and right tunnel tubes was studied by a numerical simulation method. The results showed that the surface subsidence caused by the excavation of the left (i.e., the subsequent) tunnel tube was larger, and the maximum surface subsidence occurred at the right (i.e., the first) tunnel tube. The surrounding rock on the middle wall was the sensitive part of the tunnel excavation, the stress of the surrounding rock at the left spandrel of the right tunnel tube fluctuated and exhibited the most complex variation, and the stress of the surrounding rock at the right spandrel of the left tunnel tube exhibited the largest variation. The excavation of the left tunnel tube had a great influence on the forces of the middle partition wall and the lining structure of the right tunnel tube, the middle partition wall was subjected to eccentric compression towards the left tunnel tube, and the stress at the left spandrel under the initial support of the right tunnel tube exhibited complex variations. The excavation of the left and right tunnel tubes had a great influence on the stability of the surrounding rock, as well as on the force-induced deformation of the middle partition wall and the support structure, within the width of the single tunnel tube span behind the tunnel working face. Due to the different construction sequences, the stress and strain at the symmetric measurement points of the middle partition wall, as well as the left and right tunnel support structures, were very different.