Experimental Study on Construction Method of Super-Large Section Tunnel

For the super-large section tunnel due to its super large span and flatness,together with the effect of various processes and excitation of surrounding rock during construction,the mechanical behavior of super-large section tunnel is quite complicated.Making use of the "CTSSSRH",the physical analogue for simulating the construction dynamic process of super-large section tunnel in different construction methods is experimented.The rule of surrounding rock displacement and strain development is studied and the reasonable construction method is put forward.     

Model test of influence of excavating new interchange tunnel on existing tunnel

In order to analyze the influence of construction of new interchange tunnel on existing tunnel, a three-dimension model test of interchange tunnel is carried out with the system of structure and surrounding rockmass of highway tunnel. Existing tunnel’s surrounding rock pressure, internal displacement and supporting internal force are measured. The results show that, firstly, excavating new tunnel has obvious influence on section Ⅰ of existing tunnel, and has little influence on section Ⅱ.All surrounding rock pressure keeps decreasing and arch bottom surrounding rock’s stability reduces. Secondly, crown and hance internal displacement manifest tensile deformation, and the deformation at crown is bigger than that at hance. Thirdly, exiting tunnel’s supporting axial force keeps increasing and supporting moment keeps decreasing. Finally, excavating new interchange tunnel has obvious influence on exiting tunnel’s surrounding rock pressure, internal displacement and supporting internal force when adjacent space is 0.25D, and it indicates that interchange tunnel’s adjacent space should be no less than 0.5D.     

Finite Element Analysis on Interaction of Neighboring Highway Tunnels under Construction

Recently, the construction of neighboring highway tunnels with small interval gets more and more in China. The construction of such tunnels proceeds usually by excavating one after another. The second tunnel is constructed with the surrounding rock disturbed by the first one. And the construction of second tunnel also has effect on the first excavated one. For revealing the interaction laws of such tunnel construction in combination with the engineering practice of Lanfeng tunnel at Jinshan Road in Chongqing, The FE numerical simulation analysis was used to study the characters of surrounding rock deformation, stress field, and plastic zone of the tunnel. From this analysis, it clearly shows that the excavation of second tunnel has significant influence on the first one. This study provides a scientific basis for design and excavation of neighboring highway tunnels.     

Study on Surrounding Rock Classification Refinement of Railway Tunnel and Application

For IV、V、VI levels of weak rock, because of different levels, The calculated load of tunnel surrounding rock according to the relevant specification was too different. Based on surrounding rock sub-classification method of current highway tunnel, the relation between the new surrounding rock classification and the elastic p-wave velocity refining that was used by railway tunnel was built. The phenomenon of elastic p-wave velocity cross overlap was avoided when surrounding rock classification was different in railway tunnel. For Ⅲ、V、V、VI levels of weak rock, the further refining was done by Vp in railway tunnel, in order to calculate primary support design pressure of surrounding rock, so the oversize difference of computation load value Between adjacent classification was avoided. Combining with a subway tunneling of Qingdao, comprehensive fuzzy identifying method is used to judge Surrounding rock classification level of refinement and adjust, which is more safe and economical for design and construction.     

Testing and modeling studies on creep characters of supports for tunnel using nonlinear constitutive model

Creep characters of tunnel supports structure is analyzed according to triaxial creep test of concrete specimen of deep tunnel supports structure adopting MTS815 hydraulic servo system. The creep parameters of nonlinear creep model are presented based oncreep curve. The finite element numerical model has been established considering tunnel construction process, creep characters of surrounding rock and support structure. The displacement characteristics, the effective stress and the maximum shear stress in different position in primary support and second lining are obtained through creep characters analysis of surrounding rock and supports structure. The features of displacement and stress dependent time of tunnel supports has visible difference comparing with discard creep effect and calculation displacement and practical monitoring results is basic concordance. The creep characters of surrounding rock and tunnel supports should be considered for deep tunnel.     

Theoretical calculation and monitoring on rock pressure of shallow-buried bilateral bias neighborhood tunnel

In order to research the tunnel rock pressure and its distribution, the mechanical model of tunnel rock pressure of shallow-buried bilateral bias neighborhood tunnel is set up based on series assumptions. The calculation theory of tunnel rock pressure is deduced, in which the construction processes of twin tunnels can be considered. Furthermore, the contact pressure between tunnel lining and surrounding rock is monitored on site at Zuan Qianmen Tunnel of Xinbao expressway, and the change law of contact pressure corresponding with time and construction processes is obtained. Meanwhile, the comparison analysis has been made between field monitoring value and theoretical value, and the result shows that the tunnel rock pressure’s mechanical model and calculation theory of shallow-buried bilateral bias neighborhood tunnel is rational, which will provides the theory foundation to tunnel design and tunnel rock pressure calculation of shallow-buried bilateral bias neighborhood tunnel.     

Elastic-Perfectly Plastic Solution of Tunnel Surrounding Rocks Using Mogi-Coulomb Strength Criterion

Reasonable choice of rock strength criteria is crucial for stress and displacement prediction and support design in tunnel engineering. Based on Mogi-Coulomb strength criterion and elastic-perfectly plastic model, analytical solutions of stress and displacement for surrounding rocks around a circular tunnel were derived The intermediate principal stress coefficient was used to present the intermediate principal stress effect. The results in this study were compared with the current solutions in the literatures and the influence of intermediate principal stress and shear strength parameters of surrounding rocks was discussed. The results showed extensive applicability and the Mohr-Coulomb strength criterion and Matsuoka-Nakai criterion are two special cases; when the intermediate principal stress coefficient b was equals to 0.5, the results indicated that the intermediate principal stress effect and its range for rock strength; the influence of cohesion and internal friction angle on the plastic radius and tunnel wall displacement was significant; Care should be taken to the effects of intermediate principal stress and shear strength parameter variations of surrounding rocks on tunnel design and construction.     

Safety Assessment of Circular Arches Tunnel Evacuation on Surrounding Geotechnical Environment

Based on the stochastic medium theory, influence on the surrounding rock and soil by tunnel excavation was studied. formula for predicting movement and deformation of rock and soil mass caused by tunnelling were deduced. And especially for the tunnel with circular arch section, half analytic solution for this problem was put forward. Furthermore, a program was developed to compute the movement and deformation of the rock and soil mass resulted from excavation. The deformation failure criterion of stochastic medium for estimating the surroundings safety was provided and was applied in an engineering example, which proved that the results of the research were reasonable and significant for the tunnel safety construction.     

The Monitor Measuring of Highway Tunnel in Natm

It is important that monitor measuring is applied in tunnel in regard to NATM. The monitor measuring of NATM was studied in the Fengmeiya Tunnel in Chongzun Express. Based on the regularity and conditions of the surrounding rock deformation of monitor measuring in site, the optimum time for primary and permanent support are obtained which averting successfully accidents in construction, enhancing the construction qualities and guidance to tunnel construction in Karst areas.     

Analysis About the Stress-strain of Rock when the Small Spacing Tunnel is Broaden or Not

On the background of Yuzhou tunnel at the airport road of Chongqing, it is one small spacing tunnel with serious bias. On` the basis of engineering geology, choose the tunnel section with bias most serious and then build the ANSYS finite element model to simulate the process of broaden. Analyse the surrounding rock displacement, stress strain and plastic zone when the tunnel is broaden or not. Conclusion that in the process of tunnel broading, the displacement of surrounding rock dome downward is big; In addition, as the influence of bias from the surrounding rock above the central rock pillars and right tunnel side wall bears big compressive stress and produces soil plastic deformation. Finally, suggest strengthening the support on the two area above-mentioned in the process of construction.     

Wind tunnel tests and numerical simulation on arches’static wind loads of half through arch bridge

Long span half through arch bridges have the flexible space structure. Wind loads on the arches are usually the key factor to the whole bridge. Taking an example of the Chongqing Caiyuanba Yangzi River Bridge in P. R. China, wind tunnel tests of single arch and double arches section models were conducted. The results of a single arch in the smooth flow show that arch drag variability is small, and the lift and moment variability are significantly large. The results of double arches testing show that the static forces of the windward arch are similar to the single arch. The three force coefficients of leeward arches vary with the space width ratio and the angle between the two arches. Static forces testing was simulated by the CFD software FLUENT. The static forces from the testing and the simulation were compared. The results show that the values match quite well with testing, and the drag forces mainly varied with the space width ratio.     

The Method on Surrounding Rock Classification for Highway Tunnel Construction Period in The Karst Areas of South China

Through the statistical analysis of analyzed the particularity of karst surrounding rock classification, finally obtained the rock classification index system of south karst highway tunnel construction based on rock strength, rock complete coefficient ,groundwater state, structural plane state the structural plane strike to tunnel influence, karst development to tunnel influence. And the model is applied to tianshengqiao tunnel and guanshang 2 tunnel with the example verification, and compared with the classification results and experts judgment to get the accuracy is 93.3%.     

Analysis on Interfacial Stress Between Surrounding Rock and Shotcrete Lining

According to the characteristics of interfacial stress between surrounding rock and shotcrete support, mechanical model of composite curved beame for support system of tunnel surrounding rock and shotcrete lining was established, considering the interfacial deformation coordination and the effects of bearing arch of surrounding rock. Then from static equilibrium of two differential elements, the differential equations for the radial displacement of composite curved beam were obtained. All analytic formulas of both interfacial stress and internal forces between surrounding rock and shotcrete lining by arbitrary distribution load were derived. And thus the mechanical condition of interface zone and the stress concentration position were obtained, which is convenient to assess the stability of surrounding rock and predict the safety. Finally, the analysis of tunnel project excavated by bench method showed that shotcrete lining made the formation of compressive stress zone in surrounding rock by transferring stress from the interface between surrounding rock and shotcrete, which is beneficial to improve the stability of surrounding rock.     

Influence Threshold Analysis on Railway Over-Cross Tunnels

Double-track railway over-cross tunnels were stuied by numerical simulation and regression analysis. A series of research on the influence of the construction of newly built tunnel to the existing one in different surrounding rock grades was carried out. According to the numerical simulation, 48 mechanical models were established, which considered various clearance, rock conditions and different construction sequences（building above or beneath existing one）. Based on regression analysis on the calculation results from the 48 models, the deformation prediction formulas for the existing tunnel's surrounding rocks and ballast bed were deduced. According to the high-speed rail allowed standard of roadbed deformation during operation, the minimum clear distance value by which the existing tunnel's operation would not be affected was recommended. Some analysis on the surrounding rock pressure's variation of the existing tunnel caused by new tunnel construction was done. Taking the variation amplitude as the evaluation criteria, a critical value of influenced clearance for railway over-crossing tunnels project is provided. Meanwhile, the results found that the tunnel cross the building had a smaller impact on itself compared with that of the tunnel which goes through the building.     

Analysis of Solid Fluid Coupling for Tunnel Excavation in Complicated Fractured Rock Masses

When tunnels are through water bearing section of fractured rock mass, a complex interaction process between rock mass deformation and fluid transportation is one of the most important reasons for water gushing, water bursting and mud bursting.To study the rock mass deformation and fluid transportation in tunnel excavation under complex geological conditions, a hydraulic model of complex crack rock mass was established from the relationship between the crack growth degree of surrounding rock in deep buried tunnel and the engineering scale, with which fracture network of different levels in rock mass could be considered simultaneously.Furthermore,a computer Fortran program was put forward to simulate the solid fluid coupling of excavation process of a deep buried tunnel.And it was found that the principal fractures had strong flowing action and network fractures had storage function and lag effect in seepage area.And the yield area of surrounding rock was increased under the coupling of seepage field and stress field.     

Deformation Monitoring and Its Control in a Shallow buried Large span Tunnel Constructed Using the Pile Beam Arch Method

Deformation monitoring and control measures of a shallow buried large span tunnel constructed using the pile beam arch (PBA) method are described, taking the North Gongti Road Station of Beijing Metro line 10 as an example. Based on the monitoring datum, the crown settlement, convergence, ground settlement of the tunnel and the bridge foundation settlement are analyzed. The results show that (1) the PBA tunneling method can restrain the ground settlement and deformation of a shallow buried large span tunnel; (2) the depth, tunnel span and pilot tunnel construction may influence the deformation of a shallow buried large section tunnel significantly; and, (3) advanced conduit grouting, timely preliminary support and permanent lining construction can reduce the deformation effectively.     

Application of Uncertainty Average Clustering Measurement Model to Classification of Tunnel Surrounding Rock

Based on the uncertainty measurement theory, a uncertainty average clustering measurement model for tunnel surrounding rock classification was established. Due to the uncertain factors in judging the engineering quality of rock masses, seven indexes, i.e., the rock grade, rock weathering degree, rock mass structure, elasticity longitudinal wave velocity of rock mass, influence degree of geological structure, development of joint fissure and ground water regime, were used as the discriminating factors. the indexes functions of unascertained measurement of 20 sets of rock samples were established, and the centre of the classification was indicated by using the average of classification of samples. The weight of indexes was calculated by entropy weight theory, and a prediction for the classification of residual tunnel surrounding rock was carried out using the rules of credible recognition. Each of the 20 sets of tunnel surrounding rockmass samples was tested according to the model, and the correctness rate is 100%. The other 10 sets of tunnel surrounding rock samples were predicted by using this model. The results show that the uncertainty measurement model classification agrees well with the actual measured ones. Therefore, it shows that the uncertaity measurement model is effective, available and can be applied to classification of tunnel surrounding rock in underground engineering.      

Rock Deformation, Stability Monitor Active Control About Excavation of Super-span Tunnel

According to the measurement during excavation of Jinzhou tunnel with four lanes in one cave which lies on the rebuilt highway from Shenyang to Dalian, this paper analyzes the rock deformation rule, discusses the reason of instability after a highway tunnel was excavated, emphasizes the necessity of the construction stability monitor and active control. The importance of support is Fresented with bolts and shotcrete to improve and enhance the carrying capability of the rock. It is necessary to insist on the rule of measurement and active control to ensure the safety and quality of tunnel construction.     

Mechanical Behaviors of Large Span Space Structures in the Construction Process

Traditional structural design emphasizes checking whether a loaded structure satisfies design requirements without considering the construction process. There is a great difference in structures between the states in construction processes and design, however. To solve the above problems, a method of nonlinear time varying mechanics was adopted to analyze the construction process of a structure. The structural characteristics in each construction stage were analyzed by time varying mechanics and the variations of internal force and displacements obtained. We conclude that designs will not be safe if the time varying effect in the construction process analysis is not considered. We offer advice on the design and construction of large span structures.     

Simulation Analysis of Spatial Distribution of Roadway′s Surrounding Rock Stress

To get the spatial distribution characteristic of roadway's surrounding rock stress, circular section roadway was taken as a case study. The solution of stress was got by using complex function method, and roadway's surrounding rock stress field was analysed after the solution of mapping space was transformed into the solution of roadway space. As a result, the visual diagram of stress field distribution of roadway's surrounding rock was obtained, which could describe intuitively stress distribution of roadway's surrounding rock at any position. Considering the influence of different radius and side pressure coefficients on surrounding rock stress field, the following conclusions have been obtainded: the peak value and direction of circular roadway's surrounding rock stress has nothing to do with the radius; when side pressure coefficient is less than 1/3,the roof can produce tensile stress; when side pressure coefficient is more than 3, the surrounding rock in two sides can produce tensile stress. And the change rule of hoop stress, radial stress, shear stress and the maximum and minimum of stress have also been generated.