Support design method for deep soft-rock tunnels in non-hydrostatic high in-situ stress field

Due to the long-term plate tectonic movements in southwestern China,the in-situ stress field in deep formations is complex.When passing through deep soft-rock mass under non-hydrostatic high in-situ stress field,tunnels will suffer serious asymmetric deformation.There is no available support design method for tunnels under such a situation in existing studies to clarify the support time and support stiffness.This study first analyzed the mechanical behavior of tunnels in non-hydrostatic in-situ stress field and derived the theoretical equations of the ground squeezing curve(GSC)and ground loosening curve(GLC).Then,based on the convergence confinement theory,the support design method of deep soft-rock tunnels under non-hydrostatic high in-situ stress field was established considering both squeezing and loosening pressures.In addition,this method can provide the clear support time and support stiffness of the second layer of initial support.The proposed design method was applied to the Wanhe tunnel of the China-Laos railway in China.Monitoring data indicated that the optimal support scheme had a good effect on controlling the tunnel deformation in non-hydrostatic high in-situ stress field.Field applications showed that the secondary lining could be constructed properly.

Research on the stability analysis and design of soil tunnel surrounding rock

The paper first analyzes the failure mechanism and mode of tunnel according to model experiments and mechanical calculation and then discusses the deficiency of taking the limit value of displacement around the tunnel and the size of the plastic zone of surrounding rock as the criterion of stability. So the writers put forward the idea that the safety factor of surrounding rock calculated through strength reduction FEM(finit element method) should be regarded as the criterion of stability,which has strict mechanical basis and unified standard and would not be influenced by other factors. The paper also studies the safety factors of tunnel surrounding rock (safety factors of shear and tension failure) and lining and some methods of designing and calculating tunnels. At last,the writers take the loess tunnel for instance and show the design and calculation results of two-lane railway tunnel.

Design and Wind Tunnel Study of a Top-mounted Diverterless Inlet

Combined with a UAV of the shape like Global Hawk, a new inlet is advanced to obtain high performance in both Radar Cross Section(RCS) and aerodynamic drag. Efforts are made to achieve this goal such as adopting a top-mounted inlet configuration, utilizing the diverterless technique and putting forward a new shape of entrance. A design method is brought forward and verified by wind tunnel tests. Results indicate: (1) Despite the negative effect of the front fuselage and the absence of the conventional boundary diverter, the performance of the top-mounted diverterless inlet advanced here(Ma:0.50-0.70, α:-4°-6°,σ>0.975) is equivalent to that of conventional S shaped inlet with diverter; (2) The integration of the inlet with the fuselage is realized by the utilization of a special inlet section and the diverterless technique, which disposes the whole inlet in the shield of the head of UAV, improving the drag characteristics and the stealthy performance of the aircraft; (3) The bump which is equal to the local boundary layer thickness in height can divert the boundary layer effectively. As a result, no obvious low total pressure zone is found at the outlet of the inlet; (4) According to the experimental results, negative angle of attack is favorable to the total pressure recovery and positive angle of attack is favorable to the total pressure distortion, while yaw brings bad effects on both; (5) The design of cowl lip is of great importance to the inlet performance at yaw, therefore, further improvement of the inlet performance will rely on the lip shapes of the cowl chosen.

Study on anti-faulting design process of Urumqi subway line 2 tunnel crossing reverse fault

For the tunnel crossing active fault,the damage induced by fault movement is always serious.To solve such a problem,a detailed anti-faulting tunnel design process for Urumqi subway line 2 was introduced,and seven three-dimensional elastic-plastic finite element models were established.The anti-faulting design process included three steps.First,the damage of tunnel lining from different locations of fault rupture surfaces was analyzed.Then,the analysis of the effect on tunnel buried depth was given.Finally,the effect of the disaster mitigation method on the flexible joint was verified and the location of the flexible joint was discussed.The results show that when the properties of surrounding rock at the tunnel bottom grows soft,the tunnel deformation curve is smoother and tunnel damage induced by fault movement is less serious.The vertical displacement change ratio of secondary linings along the tunnel axis may be the main factor to cause shear damage to the tunnel.The interface between the hanging wall and fracture zone is defined as the most adverse fault rupture surface.The tunnel damage was reduced with the decrease in the tunnel buried depth as more energy was dissipated by overburden soil and the differential uplift zone of soil became more diffuse.The method of the flexible joint can reduce the tunnel damage significantly and the disaster mitigation effect of different locations on the flexible joint is different.The tunnel damage is reduced by the greatest degree when the flexible joint is located on the fault rupture surface.

Overall Design of Low-carbon Campus Landscapes

In view of the global warming and the significant role of campus environment in a city, the traditional "high-carbon" urban development pattern has to be improved through exploring a low-carbon urban planning and sustainable development mode. This study focused on the overall design of low-carbon campus by elaborating the concept of overall campus design, campus planning, functional layout, landscape and architectural design, traffic organization, energy conservation and expansion of carbon sink.

The Overall Design of Land-Use Information System Based on GIS

The land-use information system (LUIS) is a special geographical information system developed under the support of the geographical information system (GIS). It effectively combines the quantitative analysis with space analysis, mixes the feature of the land-use data and figure de scription, achieves the mutual transfer of the data and figure, and provides some effective methods for the quantitative research and space analysis. The targets, methods and procedures of the overall design of LUIS and its structure function and characteristic are presented in this paper. It pro vides the guide and references for developing the special GIS suitable for the demand of land-use management.

Geotechnical investigations and remediation design for failure of tunnel portal section： a case study in northern Turkey

Mass movements are very common problems in the eastern Black Sea region of Turkey due to its climate conditions, geological, and geomorphological characteristics. High slope angle, weathering, dense rainfalls, and anthropogenic impacts are generally reported as the most important triggering factors in the region. Following the portal slope excavations in the entrance section of Cankurtaran tunnel, located in the region, where the highly weathered andesitic tuff crops out, a circular toe failure occurred. The main target of the present study is to investigate the causes and occurrence mechanism of this failure and to determine the feasible remedial measures against it using finite element method(FEM) in four stages. These stages are slope stability analyses for pre-and postexcavation cases, and remediation design assessments for slope and tunnel. The results of the FEM-SSR analyses indicated that the insufficient initial support design and weathering of the andesitic tuffs are the main factors that caused the portal failure. After installing a rock retaining wall with jet grout columns and reinforced slope benching applications, the factor of safety increased from 0.83 to 2.80. In addition toslope stability evaluation, the Rock Mass Rating(RMR), Rock Mass Quality(Q) and New Austrian Tunneling Method(NATM) systems were also utilized as empirical methods to characterize the tunnel ground and to determine the tunnel support design. The performance of the suggested empirical support design, induced stress distributions and deformations were analyzed by means of numerical modelling. Finally, it was concluded that the recommended stabilization technique was essential for the dynamic long-term stability and prevents the effects of failure. Additionally, the FEM method gives useful and reasonably reliable results in evaluating the stability of cut slopes and tunnels excavated both in continuous and discontinuous rock masses.

Analysis of the interaction between bolt-reinforced rock and surface support in tunnels based on convergence-confinement method

To investigate the interaction of the bolt-reinforced rock and the surface support,an analytical model of the convergence-confinement type is proposed,considering the sequential installation of the fully grouted rockbolts and the surface support.The rock mass is assumed to be elastic-brittle-plastic material,obeying the linear Mohr-Coulomb criterion or the non-linear Hoek-Brown criterion.According to the strain states of the tunnel wall at bolt and surface support installation and the relative magnitude between the bolt length and the plastic depth during the whole process,six cases are categorized upon solving the problem.Each case is divided into three stages due to the different effects of the active rockbolts and the passive surface support.The fictitious pressure is introduced to quantify the threedimensional(3D)effect of the tunnel face,and thus,the actual physical location along the tunnel axis of the analytical section can be considered.By using the bolt-rock strain compatibility and the rocksurface support displacement compatibility conditions,the solutions of longitudinal tunnel displacement and the reaction pressure of surface support along the tunnel axis are obtained.The proposed analytical solutions are validated by a series of 3D numerical simulations.Extensive parametric studies are conducted to examine the effect of the typical parameters of rockbolts and surface support on the tunnel displacement and the reaction pressure of the surface support under different rock conditions.The results show that the rockbolts are more effective in controlling the tunnel displacement than the surface support,which should be installed as soon as possible with a suitable length.For tunnels excavated in weak rocks or with restricted displacement control requirements,the surface support should also be installed or closed timely with a certain stiffness.The proposed method provides a convenient alternative approach for the optimization of rockbolts and surface support at the preliminary stage of tunnel design.

Determination of horizontal and vertical design spectra based on ground motion records at Lali tunnel, Iran

Most acceleration diagrams show high levels of unpredictability, as a result, it is the best to avoid using diagrams of earthquake acceleration spect~＇a, even if the diagrams recorded at the site in question. In order to design earthquake resistant structures, we, instead, suggest constructing a design spectrum using a set of spectra that have common characteristics to the recorded acceleration diagrams at a particular site and smoothing the associated data. In this study, we conducted a time history analysis and determined a design spectrum for the region near the Lali tunnel in Southwestern Iran. We selected 13 specific ground motion records from the rock site to construct the design spectrum. To process the data, we first applied a base-line correction and then calculated the signal-to-noise ratio （]~SN） for each record. Next, we calculated the Fourier amplitude spectra of the acceleration pertaining to the signal window （1）, and the Fourier amplitude spectra of the associated noise （2）. After dividing each spectra by the square root of the selected window interval, they were divided by each other （1 divided by 2）, in order to obtain the ~SN ratio （filtering was also applied）. In addition, all data were normalized to the peak ground acceleration （PGA）. Next, the normalized vertical and horizontal responses and mean response spectrum （50%） and the mean plus-one standard deviation （84%） were calculated for all the selected ground motion records at 5% damping. Finally, the mean design spectrum and the mean plus-one standard deviation were plotted for the spectrums. The equation of the mean and the above-mean design spectrum at the Lali tunnel site are also provided, along with our observed conclusions.

Optimization Design of Open Spaces Based on Wind Tunnel and CFD Simulation： Case Study of a Street Canyon in Northern China

Airflow in open spaces can significantly affect spatial quality. Therefore, according to the type of building structures, the airflow also has different forms. Studies have been conducted on the relation between airflow and pedestrian comfort; however, only few of them have focused on comprehensive urban planning that considers different weather conditions and people＇s ability to adapt. This research focuses on the differences in wind conditions caused by different spatial forms in different seasons. On the basis of a field survey in both summer and winter in a public open space, evaluation standards developed from environmental meteorological data and public feedback were used to evaluate simulation results. Next, several assumptions about canyon orientation and building types were proposed. Wind tunnel and CFD （computational fluid dynamics） simulations were conducted to evaluate the assumptions. The results showed that the canyon orientation significantly affected overall wind conditions and different building structures affected airflow. This research also provides a method to evaluate urban areas that have complicated wind environments.

Research on the optimal design of spillway tunnel

In order to meet the needs of various tasks of water conservancy project, tunnel excavation under the ground, called hydraulic tunnel. Hydraulic tunnel according to the functions of flood discharge, water diversion, irrigation, water supply, and the construction diversion tunnel of desilting emptying. Nowadays, water conservancy project on flood discharge runnel design requirements more and more high, so the factors taken into account the amount of spillway tunnel engineering, engineering cost, structure design and other factors to evaluate nature of the spillway tunnel is very important. Therefore, in actual construction, of spillway tunnel of optimization design, whether from the economic point of view, or from the point of view of safety and applicability are necessary. This article mainly from the overall layout of flood discharge tunnel, structure design and so on, and then discuss the optimization scheme.

Causal Analysis on the Lining Exfoliation and Treatment Design of an Operational Tunnel

According to the actual situation of the secondary lining of a expressway tunnel in Chongqing,this paper analyzed the specific reasons for lining exfoliation with corresponding test reports.According to this,a quick treatment scheme for lining exfoliation is proposed,which can make the treatment timely and effective,and suggestions for treating similar diseases in tunnels are put forward,which can provide reference for similar projects.

Trend analysis and comparison of basic parameters for tunnel blast design models

One of the most important factors influencing on a tunnel blast efficiency is the proper design of blasting pattern. Among blasting parameters, blasthole diameter and tunnel face area are more significant so that any change in these parameters could finally affect on specific charge and specific drilling. There are mainly two groups of methods for tunnel blast design categorized based on the parallel cuts and angular cuts. In this research, a software for tunnel blast design was developed to analyze the effect and sensitiveness of blasthole diameter and the tunnel face area on blasting results in different blast design models. Using the software, it is quickly possible to determine specific charge, specific drilling and number of blastholes for each blast design model. The relations between both of blasthole diameters and the tunnel face area with the above parameters in different blast design models were then investigated to yield a set of equations with the highest correlations to compare the methods. The results showed that angular method requires more blasthole numbers than parallel method in similar condition(blasthole diameter and tunnel face area). Moreover, the specific charge values yielded by the two methods are approximately the same and very close together.

An efficient probabilistic design approach for tunnel face stability by inverse reliability analysis

In order to maintain the safety of underground constructions that significantly involve geo-material uncertainties,this paper delivers a new computation framework for conducting reliability-based design(RBD)of shallow tunnel face stability,utilizing a simplified inverse first-order reliability method(FORM).The limit state functions defining tunnel face stability are established for both collapse and blow-out modes of the tunnel face failure,respectively,and the deterministic results of the tunnel face support pressure are obtained through three-dimensional finite element limit analysis(FELA).Because the inverse reliability method can directly capture the design support pressure according to prescribed target reliability index,the computational cost for probabilistic design of tunnel face stability is greatly reduced.By comparison with Monte Carlo simulation results,the accuracy and feasibility of the proposed method are verified.Further,this study presents a series of reliability-based design charts for vividly understanding the limit support pressure on tunnel face in both cohesionless(sandy)soil and cohesive soil stratums,and their optimal support pressure ranges are highlighted.The results show that in the case of sandy soil stratum,the blowout failure of tunnel face is extremely unlikely,whereas the collapse is the only possible failure mode.The parametric study of various geotechnical uncertainties also reveals that ignoring the potential correlation between soil shear strength parameters will lead to over-designed support pressure,and the coefficient of variation of internal friction angle has a greater influence on the tunnel face failure probability than that of the cohesion.

Seismic Design of ＂Qaf Murrizi＂ Tunnel： The Design of Tunnels in Heterogeneous Areas

Recently based in the performance of tunnels under seismic movements a good progress is made in the seismic design of tunnels. The majority of problems in the tunnel structures take place in near fault conditions and in the case of great variation of rock properties. Not having a previous experience in the seismic design of the tunnels that pass through tectonic zones with very large heterogeneity （strong rock-soil or very poor rock that behaves like soil） this article presents the general aspects of seismic calculation of tunnels and application in a specific example. The article presents the methods of seismic input modeling, design and particularities of numerical calculations. The geological conditions in which the case study tunnel will be constructed are very common in Albanian territory and represent one of the most difficult cases for the construction of road tunnels. The applied approach for using the longitudinal models for generating time histories of acceleration that can be used as input for transversal models is very simple and will help the designers for the seismic analysis of other tunnels that will be constructed in Albania.

The Significance of the Overall Design Department Thoughts of QIAN Xuesen in the New Era

The most distinctive feature of the new era is integration and innovation. With the rapid development of information technology and big data technology, the data era brought by artificial intelligence is coming. The systems engineering theory and methods summarized from engineering practice show more and more its importance and indispensability. The overall design department thoughts founded by scientist QIAN Xuesen is the result of the practice of systematic engineering science theory. The new development of the overall design department will inject intellectual support and technical support into the modernization of the national governance system and capabilities.

New Method ＆ Practice of SegmentalStructure Design fo r Ultra-Deep Shield Tunnel

The study on the mechanism ofthe super-diameter shield tunnel with 60 m burieddepth is carried out. With the background of SouthHongmei Rd. Tunnel project, it is the first time tocapture the soil pressure data of the tunnel structureunder the depth condition and to find out the loaddistribution law of ultra depth shield tunnel throughthe in-situ measurement method. By presentingthe new internal force calculation model of tunnelstructure, the structural design theory of ultra-deepburied shield tunnel is improved. Because of thenew method in this project, the amount of segmentcontaining steel is obviously reduced with creatinggreat economic benefits, which may provide newmethod ＆ basis for the design of similar tunnelengineering in soft soil area.

Dynamic Response of Foundations during Startup of High-Frequency Tunnel Equipment

The specialized equipment utilized in long-line tunnel engineering is evolving towards large-scale,multifunctional,and complex orientations.The vibration caused by the high-frequency units during regular operation is supported by the foundation of the units,and the magnitude of vibration and the operating frequency fluctuate in different engineering contexts,leading to variations in the dynamic response of the foundation.The high-frequency units yield significantly diverse outcomes under different startup conditions and times,resulting in failure to meet operational requirements,influencing the normal function of the tunnel,and causing harm to the foundation structure,personnel,and property in severe cases.This article formulates a finite element numerical computation model for solid elements using three-dimensional elastic body theory and integrates field measurements to substantiate and ascertain the crucial parameter configurations of the finite element model.By proposing a comprehensive startup timing function for high-frequency dynamic machines under different startup conditions,simulating the frequency andmagnitude variations during the startup process,and suggesting functions for changes in frequency and magnitude,a simulated startup schedule function for high-frequency machines is created through coupling.Taking into account the selection of the transient dynamic analysis step length,the dynamic response results for the lower dynamic foundation during its fundamental frequency crossing process are obtained.The validation checks if the structural magnitude surpasses the safety threshold during the critical phase of unit startup traversing the structural resonance region.The design recommendations for high-frequency units’dynamic foundations are provided,taking into account the startup process of the machine and ensuring the safe operation of the tunnel.

Estimation of tunnel axial orientation in the interlayered rock mass using a comprehensive algorithm

The axial selection of tunnels constructed in the interlayered soft-hard rock mass affects the stability and safety during construction.Previous optimization is primarily based on experience or comparison and selection of alternative values under specific geological conditions.In this work,an intelligent optimization framework has been proposed by combining numerical analysis,machine learning(ML)and optimization algorithm.An automatic and intelligent numerical analysis process was proposed and coded to reduce redundant manual intervention.The conventional optimization algorithm was developed from two aspects and applied to the hyperparameters estimation of the support vector machine(SVM)model and the axial orientation optimization of the tunnel.Finally,the comprehensive framework was applied to a numerical case study,and the results were compared with those of other studies.The results of this study indicate that the determination coefficients between the predicted and the numerical stability evaluation indices(STIs)on the training and testing datasets are 0.998 and 0.997,respectively.For a given geological condition,the STI that changes with the axial orientation shows the trend of first decreasing and then increasing,and the optimal tunnel axial orientation is estimated to be 87.This method provides an alternative and quick approach to the overall design of the tunnels.

Practice Research on Standardization of Undergraduate Graduation Design of Tunnel and Underground Engineering

Graduation project(thesis)is an important practice part in undergraduate education,which forms an organic whole with theoretical teaching link,and it is the continuation,deepening and examination of the theoretical teaching part.This paper focuses on the constitution that the lack of quality standards for undergraduate graduation design,resulting in different depth and breadth standards;the graduation design materials are scattered and lack of standardization,which leads to the lack of systematic reference materials for students,taking the tunnel and underground engineering major as an example,this paper carries out the practice research on the standardization of the graduation design of tunnel and underground engineering through investigation and combining the teaching resources accumulated in the past decades.Through the study of practice,the content of undergraduate graduation design of tunnel and underground engineering is standardized,the breadth and depth of graduation design is defined,and the“Guide for undergraduate graduation design of tunnel and underground engineering”is organized and compiled,which can provide reference for the standardization and guidance of undergraduate graduation design of tunnel and underground engineering.