Vault Settlement Research Articles

Research on Spacial Displacement Regulations in Soft Surrounding Rock Tunnel

Based on the engineering background of Dongkeling tunnel of Guizhou-Guangzhou high-speed rail, construction process in soft surrounding rock is simulated by using finite difference software——FLAC according to large-deformation characteristics in water-rich and weathering altered granite weak surrounding rock. Several aspects, such as vault settlement, invert uplift, clearance convergence, surface settlement, the maximum and minimum principal stress of the initial support and plastic zone of surrounding rock, are analyzed to determine the tunnel stability with different construction methods.

Optimization of Excavation Method in Portal Section of Neighborhood Tunnel Based on the Monitoring Results

Based on the excavation of portal section in Linwu neighborhood tunnel, items of the blasting vibration, vault settlement and level convergence are measured in the field construction. And according to the actual exposed surrounding rock, the finite element analytical model is established. The results of monitoring measurement and numerical analysis indicate that, under the circumstances of advance large pipe-shed roof support and varied surrounding rock, the original excavation method is not reasonable, still existing the optimization space. The construction of changed step method is feasible, which reflects the requirement of dynamic design and construction in New Austrian Tunneling Method.

The 3D Numerical Simulation and Settlement Control Study for City Tunnel Crossing High Fill Geological Area of Gravelly Soils

Three-dimensional finite element model of tunnel-soil-structures interaction was set up to analyze the causes of settlement and structural cracking when tunnel crossing complex gravelly soil area. It simulated the real tunnel excavation process of Chongqing Metro Line 3. Based on analysis and monitoring results, improved technical measures were used to control settlement, such as advance strengthening, excavation speed control and so on. The latest monitoring results indicate that vault and ground settlement are controlled, and convergence value is reduced significantly. The 3D numerical simulation analysis method provides reference for similar projects, and improvement of technical measures is conducive to settlement control.

Development of a new type of foam concrete and its application on stability analysis of large-span soft rock tunnel

The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock. The development of a new type of foam concrete which has the property of high compressibility and low ductility was introduced. And it was made as filling material of reserved deformation layer between the first lining and the second lining used in large-span soft rock tunnel. The effect of the new type of foam concrete was simulated as filling material of reserved deformation layer using numerical simulation. Through the comparison with the common large-span soft rock tunnel, the vault settlement and surrounding convergence are reduced by about 61% and 45%, respectively, after creep of 100 a. And in the second lining, the plastic zone reduces apparently and the maximum equivalent plastic strain decreases relatively. So, it can be found that the application of the new type of foam concrete as the filling material of reserved deformation layer can relieve the excessive force in second lining induced by rock creep, reduce its deformation and improve the stability of tunnel.

Monitoring Measurement of Vehicular Tunnels and Finite Element Numerical Simulation Analysis

The vault settlement, the horizontal convergence of Fangdoushan tunnel are monitored and measured. The changing curves with time are drawn; while the data of convergence measurement is analyzed with linear regression. The whole constructing process is simulated to analyze based on FLAC3D. The results of comparative analysis of the data from field monitoring and the data from numerical simulation shows that the simulation results accord well with the actual monitoring data, which will furthermore optimize both the design and the scientific construction

Deformation and Stability Study of PBA Extension Method Based on Air Defense Tunnel

Jiaohua Square Station of Harbin Metro Line 1 is built by PBA method with the existence of No. 7381 air defense tunnel. In order to control the ground settlement during PBA construction, numerical model is performed to analyse the surrounding rock pressure, plastic zone and structure internal force. The result shows the lower pilot headings have stronger impact on existing tunnel than the upper ones in that the lower ones get the loading effect while the upper ones the unloading effect. The internal force of air defense tunnel and ground displacement can be well controlled by reducing the area of lower pilot headings at the stages of pilot heading excavation, but the final surface settlement is unqualified. The scheme of lower big pilot heading in part with the support of portal frame meets the requirement of surface settlement. The in-situ surface settlement and the vault settlement of defense tunnel are essentially consistent with numerical results.

Finite Element Analysis for the Displacement Characteristics of Loess Tunnel with Weak Surrounding Rock

Backed up by Dayoushan loess tunnel of Xining in Qinghai province, the displacements of vault settlement, peripheral convergence, surface deformation and post-construction settlement caused by tunnel construction are numerically simulated and analyzed. First, 2-D elastic-plastic model is founded to simulate the tunnel excavation process with up and down steps method. Second, considering the rheological characteristics of loess, 2-D visco-elastic-plastic constitutive model is founded to simulate the creep deformation of rock displacement characteristics. Finally, combined with the serious collapsible feature of loess foundation in supported project, the post-construction settlements under different conditions are simulated to obtain the settlement values of tunnel vault and bottom. The results can explain the deformation laws of tunnel displacement characteristics reasonably and show the importance of foundation reinforcement measures for loess tunnel.

Analysis of Force Mechanism and Reinforcement Effect of Leading High Pressure Grouting Ductule Basing on Numerical Simulation

In order to study the force mechanism and reinforcement effect of high-pressure second grouting method in leading support of soft-fracture wall rock, with the example of Heishiling highway tunnel construction at the shallow depth and crushed zone of the tunnel’s exit, which belongs to Zhangshi highway in Hebei province, by Three-Dimensional Numerical Simulation of GTS (Ground and Tunnel Analysis System), monitoring and surveying method, force mechanism and wall rock convergence were simulated and measured experimentally. The results showed that ductule high-pressure second grouting combined with double side-wall heading excavation method achieved good results, the maximal vault subsidence is 18.5mm, the maximal uplift value of inverted arch is 17.8mm, and the maximum displacement value on both sides of the wall is 15.9mm.

Feasibility Study on Step Method Excavation of Tunnels with Large Cross Section and Small Interval

Abstract Based on the analysis of monitoring data in the construction of Linwu Tunnel and the numerical simulation of construction sequences by software Ansys, the paper calculated values of ground settlement and vault settlement in program of step method excavation; and analyzed the influences between excavation program and ground settlement, as well as vault settlement. It is feasible to use the program of step method excavation in areas of V-class surrounding rocks in Linwu Tunnels with large cross section and small interval, which offers great reference value to other similar projects.

Excavation Effect of Tunnel Slope Reinforced with Anti Sliding Pile in Cold Regions Based on 3D-FEM

In order to analyze the effects of tunnel excavation on the stability of tunnel slope reinforced with anti sliding pile and establish 3D elastic-plastic finite element model, the paper focused on the analysis of the deformation of the structural system, the characteristics of the deformation and the rules of the plastic zone of the surrounding rock. The results showed that in the construction process, the maximum vault settlement was about 28mm; the plastic zone occurred mainly in the place surrounding the sliding pile and part of the earth surface, the plastic zone around the vault at the entry of the tunnel was large and tended to connect with the earth surface; the soil arching effect ensured the stability of the slope during the tunnel excavation and construction.

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

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

Study on Optimization of Core Pillar in Large-Span Tunnel Excavated with Double-Side Heading Method

Based on the undergroundHongtudistation of Chongqing Rail Transit Line VI, stress and plastic strain of surrounding rock, internal forces of supporting structure and vault settlement are calculated in different widths of core pillar. Comprehensive analyses indicate that there is an optimal value of core pillar width in the construction of tunnel with the double-side heading method. Width of core pillar, 0.3 times as large as the tunnel span, is suggested in other projects with the same construction method, which is of great significance in practices.

3D Simulation of Tunnel Collapse Consolidation and <i>In Situ</i> Monitoring Analysis

A shallow buried tunnel was collapsed during construction. According to the actual situation of the tunnel, different collapse consolidation schemes were put forward and corresponding three-dimensional finite difference numerical models were established and analyzed using FLAC3D software. Base on the 3D Simulation results, a collapse consolidation scheme was determined and constructed. The in-situ monitoring results of vault subsidence and convergence displacement were consistent approximately with the 3D Simulation results. The in-situ measured results were in line with the specification’s allowance and show that the consolidation effect of reinforced concrete casing arch and ahead grouting method is good. This could be referenced for similar engineering.

The Application of Adaptive BP Neural Network on Numerical Prediction on Tunnel Vault Subsidence Based on the Moving Average

Tunnel vault subsidence is a very complex nonlinear dynamic system whose feature is difficult to describe accurately by traditional methods. In this paper, the moving average model of time series and the adaptive BP neural network are adopted to build the model, which use smoothing method of time series to curb and weaken the error in field surveying data, in an effort to reduce the numerical fluctuations of time series and use the adaptive learning rate and the momentum method to improve weaknesses of easily trapped into local minima, slow convergence and other shortcomings in the BP neural network. The prediction examples show that the model based on the moving average and the adaptive BP neural network can effectively restrain and weaken the measurement error and the method has features of simple, fast convergence and high accuracy prediction. Therefore, this method can be widely used.

Influence of underground water seepage flow on surrounding rock deformation of multi-arch tunnel

Based on a typical multi-arch tunnel in a freeway, the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) was used to calculate the surrounding rock deformation of the tunnel under which the effect of underground water seepage flow was taken into account or not. The distribution of displacement field around the multi-arch tunnel, which is influenced by the seepage field, was gained. The result indicates that the settlement values of the vault derived from coupling analysis are bigger when considering the seepage flow effect than that not considering. Through the contrast of arch subsidence quantities calculated by two kinds of computation situations, and the comparison between the calculated and measured value of tunnel vault settlement, it is found that the calculated value(5.7–6.0 mm) derived from considering the seepage effect is more close to the measured value(5.8–6.8 mm). Therefore, it is quite necessary to consider the seepage flow effect of the underground water in aquiferous stratum for multi-arch tunnel design.