Tunnel Management, Emerging Technologies, and Innovation

Stratum environmental damage induced by urban tunnel construction is almost inevitable, which makes structures, roads and underground pipelines work improperly. This paper described the formula and details of development of a computer system. A prediction and control system for environmental damage induced by tunnel construction, named STEAD-RISK, was developed and introduced in this paper. This system had been developed in Delphi programming environment, by classical predict formulations, numerical analysis and three-dimensional imagery technology, prediction results and engineering field data was saved in database of this system, and then transfer was changed to visual three-dimensional maps. The main emphasis in this study was placed in developing calculation method and conversion between database from the system and points on the map. A newly computing package was developed in this program, which could predict settlement in construction site. By three-dimensional simulation, this code could transform predicted and monitored data into visual three-dimensional maps, in which the influence caused by construction to the stratum environment could be simulated veritably, so it's helpful for damage predictions and safe precautions. Finally, the paper presents a case application of the new system (Chinese version) in Beijing subway project.

Minzhi station foundation pit in Shenzhen subway is adjacent to Pingnan railway. There is obvious unsymmetrical loading above the pit, and the pit is affected by the dynamic load from train. Therefore, the impact of pit excavation on the railway and the safety of the pit itself must be paid close attention to. The main technical measures adopted in the design and construction of deep foundation pit adjacent to railway is introduced. The measures include using steel pipe piles and prestressed anchor cables to reinforce the railway embankment, using diaphragm wall in the building envelope, setting strand prestressed cables in the middle of the diaphragm wall, using sleeve valve pipe grouting to reinforce the soil, and so on. The settlement of the railway embankment and track, as well as the horizontal displacement of the diaphragm wall, is monitored. Monitoring results show that these technical measures can ensure the normal operation of the railway and the safety of the pit itself.

Different computing models are compared through analyzing post-earthquake serviceability of a water conveyance tunnel of a practical hydraulic engineering and appropriate model is recommended. In the analysis of performance after seismic loading of tunnel, contact surfaces are employed to simulate the interface of lining and surrounding rock, different ground models and boundary conditions are adopted, unequal grade of wall rocks are considered and various methods are used to take the water-tunnel interaction into account. The distribution of cracks and whether the crack is open or closed are obtained, and the post-earthquake performance of tunnel is evaluated. Computed results from different models, methods and conditions are compared and analyzed, influences of various factors on computation are concluded, and finally a simplified method with enough precision is suggested. The analysis and rules in the paper can provide a reference for evaluation of post-earthquake serviceability of tunnels, and suggested analytical method can be applied in similar engineering.

Tunnels are often located in complex geological environments and are subject to both during and after construction defects. Cracking of the tunnel lining is one of the most common and serious defects occurring in tunnels. It reduces the durability of the concrete lining and ultimately, the durability and structural performance of the whole tunnel. In this study, both the quality and cracking of the concrete lining of a railway tunnel in Hunan Province (China) was investigated using non-destructive test methods; namely the ground penetrating radar (GPR) and ultrasonic waves. Test results of these measurements including the concrete lining thickness and crack depths/width are presented in this paper. Additionally, uniaxial compressive strength testing of the concrete lining was also conducted in the laboratory and is also discussed in this paper. Based on the study findings, remedial measures were implemented to minimize further deterioration of the tunnel lining. To date, the tunnel remains structurally safe for train operations.

An operator's skill to steer micro tunneling machine is important to maintain driving within line and grade tolerances. It is also important to minimize rapid or erratic changes when steering a microtunnelling machine. This paper presents a way to evaluate the machine steering quality of operator by recording the shield machine's positions, strokes of steering hydraulic jacks, and pitch and roll values from pipe to pipe. Since the steering ability of shield machine and soil type are also important factors to influence the microtunnelling alignment. The field data are collected from various projects in which three brands of shield machines are used to drive in various ground, such as gravel formation, clay deposit, sand deposit and hard bedrock. The average deviation is evaluated from the integration of each pipe's deviation along the shield machine's traces divided by the total pipe length. The average adjustment of shield machine is evaluated from the integration of all the adjustments along the line divided by the total pipe length. It can be concluded that the average vertical or horizontal deviation is proportional to the average vertical or horizontal adjustment of steering jacks when the operator is steering shield machine in a normal and smooth conditions.

The visible space for the drivers in the long tunnel is apparently narrower compared with that along the regular roadway sections. Accordingly, the traffic control for the concerns of driving safety for the long tunnel is quite different from the traditional traffic management system. The required traffic monitoring equipments used with the long tunnel are widely specified, such as: closed circuit television (CCTV), vehicle detectors (VD), lane control sign (LCS), smoke detector (SD) and et al. The key point for the long tunnel regarding to the safety maintenance is then how to connect all the equipments working well together. Another issue for the safety of drivers within the long tunnel is how to let them know the traffic situation in advance and how to follow the guidance of the system in case of accidents occurring. This research uses the Ba-Ghua mountain tunnel, 4932m long and the longest one in central Taiwan, as an example study the strategy on the operating performance assessment for the automatic incident detection system of the highway tunnel.

As the most advanced soil improvement technique, foam modifying soil measures always be taken when the EPB shield tunneling in the water-rich sand and complex strata. Experimental research on foam-modified fine sand and coarse sand was carried out using self-developed foam agent, conclusions were drawn that foam can not only reduce the permeability coefficient and shear strength significantly, but also it can enhance the fluidity of the sand greatly; If appropriate quantity of bentonite or clay is injected in the sands, the water-holding capacity and liquidity will be further enhanced while the permeability coefficient of modified sands will be further reduced. Combining the experimental results of permeability, direct shear strength and fluidity of foam-modified sand, the corresponding quantitative indicators were proposed and it will provide reference for the parameters selection of sand modification in the shield tunneling construction. And some field experimental results of metro construction are introduced to show the performance of foam.

Different from normal tunnels, the mechanical behaviors of super large section tunnel with two bores and eight lanes are more complex and the construction methods are also diversified. Based on the maximum rock tunnel with extra-large cross section and low flat-ratio in China, the convergence and anchor bolts stress of core rock are monitored in detail. The deformation and stress characteristic of core rock under different construction stages are analyzed. Some conclusions have been drawn. Compared with the upper part, the bolt's axial stress of the middle part in the core rock is greatly affected by the construction process. The excavation of the upper-stage and down-stage has a great effect on the anchor bolt stress of core rock and those procedures are the main point to control the stability of core rock. The longitudinal incidence of the excavation of the extra-large cross section and low flat-ratio tunnel is about half time of the tunnel span, which is about 10 to 11 m. The result presented in the paper can be refereed in the design, construction and research of similar tunnel.

Xi'an City of China is one of the areas which suffered from the ground fissure disaster. Tunneling through ground fissures was seldom encountered, especially underneath an existing bridge of footing foundation. It is important to assure the safety and performance of the bridge during and after tunnel construction, especially in loess soil stratum where the ground fissures exist. The analysis and measurement of Chang'an Overpass of footing foundation in Xi'an were conducted during tunneling of Xi'an Metro Line 2. The features of ground fissures in Xi'an areas are analyzed, and the ground fissure No.6, which just go across Chang'an Overpass and differential settlement occurred along the ground fissures. An comprehensive field observations of bridge settlements, ground settlements, ground horizontal displacement, and also the tunnel convergences were conducted during tunneling. The safety of both the bridge and tunneling construction were evaluated. Based on the field observation, the interaction of tunneling, bridge and ground fissures was investigated. It is shown that a successful tunneling case history was made in the complicated conditions of overpass and ground fissures.

According to the analysis of the displacement of wall rocks and shoring in the underground laneway No. 411 of Fucun coal mine, Zaozhuang city, Shandong Province, combining with the FEM model of this underground laneway, and based on corresponding presumptions on loads of wall rock and shoring, the paper educes the loads of the laneway's wall rock which are influenced by exploitation pressure by back-analysis method. And so, the corresponding displacement of the wall rocks which can be used to estimate the stability of the wall rock along with the displacements in-situ can be worked out. For this rectangle underground laneway, the stress centralizes in the corners on the top, so do the external loads and displacements in this place. Additional conservation measures should be carried out in those corners to ensure its stability.

When a shield machine pushes forward it causes the internal structure of the ground to change. Such changes take place on the vertical, lateral, and longitudinal dimensions, and is in essence a three dimensional problem. This study used the Taipei Metro system's double shield tunnels as an example and simulated the excavation conditions of single and double shield tunnels. A three-dimensional analysis model was created using a finite element program, PLAXIS 3D Tunnel. The relationship between tunnel contraction percentage in three dimensional analysis, ground loss used by empirical methods, and ground surface settlements caused by shield tunnel construction were investigated. The relationship between ground loss and tunnel contraction percentage could be represented by a linear equation. Moreover, dual-tunnel combinations were attempted as well as a ground surface settlement curve approximation and comparison on a double shield tunnel. Other than discussing the difference between 2D and 3D tunnel behaviors, suggestions were made for the normalization relationships of 2D and 3D single tunnel contraction percentages and maximum ground surface settlements, which can provide a reference for the analysis and design of similar projects in the future.

Employing the explicit finite difference code based on strength reduction method, this paper optimizes the rockbolt length and circumferential distance of shallow double-arch tunnels subjected to unsymmetrical loads. For the geological properties of shallow and large cross section tunnels, seepage influences are considered in the stability analysis. The distribution laws of rockbolt on circumferential and longitudinal orientation respectively are presented with numerical simulation method. The results show that the longitudinal space distances of rockbolt has great influence on the horizontal displacement of hance of double-arched tunnel, and the horizontal displacement of hance increases with the increasing of longitudinal space distance. However, the circumferential space distance has effect on the ground settlement, and the ground settlement increases with the increasing of circumferential space distance. According to the stress distribution of middle wall, it is found that the safety of tunnel dose not increase with the increasing of the number of rockbolt. The reasonable rockbolt supporting parameters are given for benefiting tunnel design.

Considering the facts that the parameters of tunnel lining structures are random, that the distributions are various, and that the limit state functions are highly nonlinear, this paper estimates and presents the practical parameters of tunnel lining structures. The calculations are formulated in the framework of the information entropy and maximal entropy principle, so that the actual parameters are obtained. The failure probability and the reliability index are calculated using the parameters based on the Monte-Carlo direct sampling method. Then the stability of tunnel lining structure is evaluated by using the reliability index. According to the practical engineering, an example is given. The results, which are calculated by the Monte-Carlo direct sampling method and maximal entropy principle for tunnel lining structure, are more scientific and reliable. The present method, with a high precision and a fast velocity, is suitable for similar parameter estimation and reliability calculation.

To investigate smoke temperature properties lower tunnel ceiling by longitudinal ventilation velocities and different tunnel slopes when fire occurred in a tunnel, a series of fire tests were conducted in a reduced scaled model tunnel. The model tunnel was 52.5m length, and it had a circular cross-section with an inner diameter of 1.1m. A methanol pool was employed as a fire source. Seven tunnel slopes and four longitudinal ventilation velocities were used to simulate different fire scenarios. The smoke temperatures lower the tunnel ceiling were measured and analyzed. The variation laws of smoke temperature lower the tunnel ceiling were gained, such as the temperature at different distance from the fire source varying with time and with longitudinal distance, the maximum smoke temperature above the fire source. The results show that negative slope has bigger effect on smoke temperature under the same ventilation velocity, and the effect is more as the negative gradient increases. In the same slope tunnel, smoke temperature gradually diminishes as ventilation velocity increases. When the longitudinal ventilation velocity is 1.34 m/s, the smoke temperature of the upstream section of fire source is tendency to normal temperature.

According to the position of burned train and the location of fire, the numerical simulation of smoke flow controlling was carried out in railway shield tunnel when a train caught fire to stop in the slope section being -3%. Tunnel fans fixed at the rear ingress are immediately to supply fresh air along tunnel, and the fans at the front exit to exhaust smoke. So there exists a great volume of wind along to take smoke outside the tunnel. Large eddy simulation was employed to simulate the smoke temperature, visibility and carbon monoxide concentration distribution in tunnel, at ventilation velocity of 1m/s, 2m/s, 3m/s and 4m/s, respectively. The results show that emergency ventilation policy, 3m/s, can effectively ensure passengers safe evacuation facing with fresh air, and the high temperature smoke under the ceiling do not damage tunnel lining structure. So the emergency ventilation policy is right and the evacuation plan is correct.

The bearing capacity of foundation above tunnel depends on the soil physical mechanics and its seepage properties, the bearing capacity and the seepage properties of the lining of tunnel and the consolidation degree of the soil layer resulted in the pore pressure dissipation. Using finite difference software FLAC3D, the process of the shield tunneling and supporting and the bearing capacity of foundation are simulated. The pore pressure of the soil layer and the surface settlement in different loading are obtained. By comparing these mechanical characteristics, the capacity of the foundation above tunnel in the range of the fine silty sand layer is proposed.

The finite element method provides a powerful tool for nonlinear numerical analysis of engineering structures. Although significant progress in the constitutive modeling of concrete and shotcrete behaviour has been made, very few of these models deal with the effect of high temperature on concrete or shotcrete. This research work developed a relatively comprehensive and sophisticated model, the Willam-Wranke five-parameter model, to describe concrete as well as shotcrete deformational and strength behavior under normal and high temperatures. A highly sophisticated Isoparametric Sandwich Shell Element (ISSQ) model that can have many layers is very useful for simulating the behavior of the shell structures, because it has the ability to separately specify a different material as well as different properties for each layer. The model also has the ability to specify a different temperature for each layer as well as constant or linear temperature distribution through the element thickness, which will be helpful for fires in tunnel structures. The model was applied to a tunnel for the case of fire loading. This helps answer many questions about the safety of tunnels in case of fire. The results show that taking fire loading into consideration is of great importance when designing concrete tunnel lining, because very high temperatures can cause total failure in some parts of the tunnel lining.

Firstly, the rationale of block theory and stochastic statistical method of rock joint structural planes were introduced, and the reformatory measure of the Genetic Algorithm was brought forward. Secondly, the change of the position, size and stability in differ trend of the tunnel in twp groups of typical joint structure planes were simulated and analyzed based on the key block theory and stereographic projection method, and they were contrasted and analyzed in contrast with practical instance. At last, the best trend of the tunnel in the characteristic interval of joint structure planes was programmed and reckoned by using reformatory measure of the genetic algorithm. The results obtained show that it is economic and feasible to optimize tunnel's axis by using key block theory and the modified genetic algorithm, and it is very stated referenced worthiness in traffic programming, design and construction of the tunnel.

The effect of tunneling on existing buried pipes is a problem which engineers designing and practicing in urban geotechnical environments encounter more frequently than in the past. However, previous methods are usually based on the assumption that the ground is homogeneous. This paper presents displacement controlled method to analyze the tunnel-soil-pipe interaction based on the layered half space soil model, which can solve the problem subjected to multi-layered non-homogeneous soils. The accuracy of the proposed method is verified by the results from displacement controlled finite element method. The results discussed in this paper indicate that the proposed method is a valid approach with higher precision to analyze response of existing pipe induced by tunneling in the layered soils and the effects of soil stratification should be considered.

The soft rock tunnel arch effect, which is the theoretical basis for the structural system of the anchor support, plays a direct impact on its stability. How to identify the arch-effect has been a problem. Assuming isotropic rock mass, the method (Strain Criterion of Arch-effect) is put forward that the arching distribution can be determined by the relative strain distribution of the rock on the top of tunnel vault. This paper points out rock Poisson's ratio is another important factor for arch-effect. Considering the different physical and mechanical parameters of rock and sprayed concrete, the changing regularity of the tunnel arching-effect is analyzed with the 3D-FEM model. Suggestions are to make full use of the arch effect in the design of bolting and shotcrete lining structural system in tunnel excavation.

Behavior of circular pressure tunnel lining is analyzed by Reinforced Concrete Finite Element Method (RCFEM) and following characteristics are found: the maximum width dose not occur at the highest head; cracking hydraulic head increases while surrounding rock have larger deformation modulus, but the maximum crack width do not vary apparently; crack width in lining can be controlled effectively while inner reinforcement is more than outer reinforcement and there are steel bars in the middle of lining; lining bears less forces actually after cracking than linear calculation because of the loss of stiffness; the reinforcement of lining is determined by the crack width control requirement, but existing formula of crack width are not appropriate for lining of tunnel. On the basis of above characteristics, RCFEM is suggested for lining design. The key of the method is that crack width is calculated by FEM directly and amount and distribution of steel bars are determined by allowed maximum crack width. Finally, by an example, the process of lining reinforcement designation by RCFEM is illustrated and the reasonableness of the stress limitations of steel bar is verified.

Because of geological conditions and complicated construction technology, it is important to ascertain the release rate of displacement of surrounding rock during the tunnel excavation, and one of the basic data must be determined firstly during the numerical simulation of excavation. Based on the rock mechanics and excavation process, combined with on-site monitoring of the displacement data, using the FLAC^3D software to make numerical simulation and establish study examples, adopting the artificial neural network method to have the inverse analysis of the tunnel excavation and construction process, it is obtained that the release rate of displacement of surrounding rock under a reasonable construction time. It can provide the reference data for the tunnel design, construction and the numerical simulation analysis during construction under the similar conditions.

Geological defects, such as conductive faults, karst conduits, fracture zones and so on, often lead to serious water inrush disaster, because they frequently become potential water inrush passage especially when large water bearing structure exists. This will cause high construction risks of water inrush. Water inrush process is the catastrophe evolution process of flow state for conductive fault. The initial stage of the catastrophe evolution process is the water seepage in confined aquifer, which then develops into rapid flow in the fault. The last stage manifests as conduit flow in the tunnel. Brinkman equation has been adopted for the seepage characteristic description of karst water in fault. Based on the conservation of mass and pressure balance, Darcy equation and Naier-Stokes's equation are respectively used to characterize the flow in confined aquifer and tunnel. The variation characteristics of velocity, pressure and discharge on different position of the fault have been analyzed. In addition, the permeability effect of water inrush on different faults has been modeled. It has been found that risk of water inrush becomes higher for obvious pressure relief resulting from increasing permeability.

According to the characteristics of old in-use tunnels managed by Shenyang Railway Bureau, a investigation on defects like water leaking has been carried out by video recording, unfolded drawing and Ground Penetrating Radar (GPR) scanning. The features of defects such as tunnel lining cracking, surface corrosion, freeze-thaw, water infiltration, etc. are studied carefully. Based on the above, this paper summarizes the detecting methods for water leaking, voids, debonding, delaminations and moisture, and then analyses the defects features, which lays a theoretical foundation for tunnel defects testing and treatment. The conclusion also provides guidance for engineering practice and integrated maintenance of tunnels.

In the construction of large-span and multi-arch tunnel, the advanced middle drift usually be used as the free-face of the tunnel excavating blasting, which has an adverse effect on the Middle Wall unavoidably. Most of research focus on the vibration of Middle Wall and the transmit law of the blasting vibration wave along the Middle Wall, but little take into account the concrete age of the Middle Wall. Also in the tunnel construction of III classification rock, the lining construction will lag behind the digging face to stabilize the surrounding rock and avoid the construction interference. Based on the Chenjiaqiao Tunnel of the North Expressway around Whenzhou City, the blasting effect on the Middle Wall is stimulated by using the software of ANSYS, which analysis the different vibration effects of the Middle Wall under the different concrete age conditions.

When a tunnel comes through a deep beried tunnel in rocks abounding with groundwater, the most important problem is to compute the flowrate of groundwater. The key to compute the flowrate is to choose the right calculation method according to the regional hydro-geological characteristics. Based on the hydro-geological characteristics of the Dashuijing Tunnel, this paper chose three different geological dynamic methods to calculate the groundwater flowrate. The calculation result show that when the permeability reduces, the groundwater flowrate by Railway code formula and Fuluominlang method reduces in the form of index, the groundwater flowrate also reduces with an near-linear decrease by the non-uniform section two-dimensional flow formula. By considering about the non-uniform of the rock stratum in study area, we divided the area into several pieces. According to the three different methods, we forecast the groundwater flowrate in the Dashuijing tunnel by considering about the Railway code formula and the non-uniform section two-dimensional flow formula.