Average Temperature Distribution of the Ceiling Jet in Train Fires in Tunnels

The flame ceiling jet is easily formed while the on fire train stops in the tunnel. The iterative formula is derived to calculate the average temperature of the flame ceiling jet when the fire source is set on the center of the train by establishing a one dimensional model of the unit control volume, and the heat exchange is considered among the flame smoke and the wall of the tunnel and the train. Undetermined coefficients in the iterative formula are determined by small scale model experiments with the scale factor of 1:8 and numerical simulation. The calculated values of temperature by the iterative formula are consistent well with the measured values, and the maximum error of calculation is no more than 7%, which indicates that the iterative formula is reliable. The results show that the distributions of the average temperature of flame ceiling jet are in the exponential form, but there are some differences between that above the train and that in the tunnel. Two prediction formulas for the flame ceiling jet average temperature changing along the longitudinal tunnel are obtained by the sub fitting method. The results can provide reference for the alarm parameter selection, device settings in tunnel, safety evacuation of the passenger, as well as the analysis of the destructive effects on the tunnel lining structure caused by tunnel fire.     

Field test and deformation controlling for single tunneling lining stability

The construction process of anchor,fiber concrete and its mechanical principle of interaction with surrounding rocks is studied by field tests from the view of researching stability of single layer tunneling lining. The mechanical properties of single layer lining in the practical application of tunnel engineering are measured. On the basis of this study,the mechanism of single layer tunnel lining is discussed,which is finally applied to the engineering practice,formatting a set of theoretical support for the design method of single layer lining. Studies found that close effect between fiber reinforced concrete and rock is well,which shows that the single layer lining design method to ensure quality and safety proposed in this paper is feasible,and construction characteristic of retaining structure is reliable. The method can be widely applied in engineering practice,and has remarkable economic benefit and social benefit.     

Load Calculation Method of Shallow Tunnel under Unsymmetrical Loadings in Broken Surrounding Rock

Tunnel portal section mostly faces unfavorable geologic and topographical conditions, such as broken surrounding rock, shallow and unsymmetrical loadings. The current Chinese code for design of road tunnel provides the load calculation method of tunnel under unsymmetrical. However, according to the mechanic and deformation characteristics of the tunnel lining on site, the assumption is not suitable for the shallow tunnel under unsymmetrical loadings in broken surrounding rock. Therefore, through engineering case analysis and results of three-dimensional numerical analysis, the failure mechanism of shallow tunnel under unsymmetrical loadings in broken surrounding rock is presented firstly, that is, deep buried side broken surrounding rocks slump down after excavation and squeeze the lining, which makes the lining deform outward and bear passive earth pressure. Through the failure mechanism, the surrounding rock mainly includes slumping area and passive area. Then the corresponding formulas are deduced based on limit equilibrium theory. Finally, a case study is adopted to verify the feasibility of the new method. It is show that the new method is more reasonable than the method of current code.     

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.     

Earthquake Response Properties of the Support Structure of Large Cross Section Tunnel

The response properties of displacement and stress of tunnel support structure are discussed in detail under the action of horizontal earthquake acceleration(Ya),longitudinal earthquake acceleration(Za) and horizontal-longitudinal earthquake acceleration(YZa).This discussion is based on an analysis of the surrounding rock-support structure-earthquake interaction,adoption of an ADINA nonlinear finite element and construction mechanics,and transient dynamic time domain analysis of a large cross section tunnel.Results of analysis show that:(1) Horizontal earthquake acceleration has important influence on horizontal displacement,maximum principal stress,acceleration and velocity.(2) Longitudinal earthquake acceleration has important influence on longitudinal displacement,effective stress,maximum and minimum principal stress,maximum shear stress,acceleration and velocity.(3) When Ya=0.191g and 0.440g or Za=0.141g and their combined action,the initial support of tunnel would be damaged and the local lining would have partial damage.(4) When Ya=0.440g or Za=0.326g and their combined action,the lining of tunnel would be damaged.(5) When Ya=0.880g or l Za=0.652g,the support structure of tunnel would have severe damage.     

MODEL TEST RESEARCH ON A COMPOSITE LINING OF UNDERGROUND ENGINEERING IN JOINTED ROCK

Combined with thedesign precept of Cai-Yuan highway tunnel 2 in Chongqing,stress state,time ffectiveness and rupture mechanism of rock near the bounda-ries of the tunnel and the second lining in jointed rock mass arc studied with model tests.The results show that shotcretc-bolt support betters mechanical properties of the periphey rock of the tunnel,and increases the capacity of anti-deformation.The second lining also has the action of supporting structure.     

Calculation of Crack Space and Crack Width of Tunnel Lining Based on Elastic Foundation Curved Beam Model

Based on the elastic foundation beam,the control differential equation of tunnel lining is worked out,according to the theory of Saint-Venant,the predominance equation about the center angle to the crack space is established, then the crack space of tunnel lining under the loads can be worked out and according to the crack space,the crack width can be calculated.     

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.     

节理岩体中连拱隧道施工对周边建筑物的影响

以重庆东水门大桥—千厮门大桥渝中区连接隧道为研究对象,基于UDEC软件建立离散元数值模拟分析模型,研究了城区连拱隧道施工引起的地表沉降,上部建筑物基础沉降及倾斜,新建隧道下方已有轨道六号线的变形、受力特征,并将监测数据与数值模拟进行对比分析。结果表明,连拱隧道左侧隧道上导坑施工引起的隧道拱顶沉降和基础沉降量最大,经计算上部建筑物基础最大沉降量为3.81 mm,最大倾斜量为0.02%,建筑物基础沉降量和倾斜在规范许可范围之内;隧道施工引起的地层损失使得轨道六号线左拱肩向上隆起,六号线弯矩分布规律和其变形形态基本一致,弯矩最大值位于左拱肩部位,最大值为238 kN·m;数值模拟计算结果与监测数据量值相当,变形趋势基本一致;采用UDEC软件可以准确地计算出隧道开挖过程中节理的存在对隧道周围建筑物变形的影响。     

Analysis and Control on Roof Stability of Rock-salt Cavity

Analysis and control on roof stability of rock-salt cavity are very important to ensure safety and benefit in production, build and use of repertorv of rock salt cavity. Dynamic balance process and instability process of rock-salt carity roof are studied, and instability mechanism of rock-salt cavity roof is studied with catastrophe theory, and the influencing factor are analyzed, which will be theoretical basis of rock-salt cavity stability control.     

软枣猕猴桃种质资源果实品质、表型性状多样性及主成分分析

为更好的分析、评价软枣猕猴桃种质资源多样性,对70份种质资源果实的15个性状指标进行了相关性及主成分分析。结果表明,种质间各性状变异幅度较大,类型丰富。相关性分析结果表明,一些果实性状间存在显著或极显著相关;主成分分析结果表明各性状的贡献率分散,性状变异具有多向性。其中,第1主成分主要由果实质量、果实纵径、横径、侧径及果梗长决定,第2主成分主要由果皮颜色、表皮光滑度及果形指数决定,第3主成分主要代表可溶性糖含量、可溶性固形物及维生素C含量,第4主成分反映了果实可滴定酸含量情况。因此在软枣猕猴桃育种改良过程中,第1主成分增大时有利于增大果实大小,第3主成分增大时有利于提高果实品质。     

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.     

Coupled Vibration of Saturated Fractional Derivative Type Viscoelastic Soil of a Circular Tunnel with Partially Sealed Shell Lining

Considering the compression of medium and fluid, coupled vibration of saturated fractional derivative type viscoelastic soil and a circular tunnel with partially sealed shell lining in the frequency domain is investigated according to theories of Biot and elastic shell. The stress and displacement constitutive behavior of the soil skeleton is described by fractional derivative model which reflects the rheological properties of the medium while regarding soil as a liquid-solid saturated porous medium. The expressions of displacement, stress and pore water pressure are obtained while the inner boundary of circular tunnel is subjected to axially symmetric radial traction and axially symmetric fluid pressure respectively by introducing a partially permeable boundary condition. With the parameter analysis, it is revealed that the order of fractional derivative model on the responses for the system subjected to the symmetric radial traction is much greater than that of the system under the axially symmetric fluid pressure. And resonance phenomenon occurs obviously. Nevertheless the system responses do not have remarkable resonance phenomenon under axially symmetric fluid pressure.     

考虑渗流和地震时的砂土边坡稳定性计算

基于极限平衡理论,以砂土边坡为研究对象,推导了渗流和地震存在时拟静力法和拟动力法边坡安全系数的计算表达式。通过程序求解,与已有算例对比表明,计算结果基本一致,验证了2种方法解析式的合理性。参数分析表明,水位越高,边坡失稳越严重,水力梯度与安全系数基本为线性关系。渗流方向向下时,稳定性随水力梯度的增加而增大;渗流方向向上时,变化规律相反。水平地震加速度系数对稳定性的影响剧烈,竖向地震加速度系数对稳定性影响较小,简化计算可以忽略不计。最终得出拟静力法的解析式,简单、实用,而拟动力法则可以更为全面地考察砂土边坡稳定性随时间变化的特点。     

Clipping Performance of Advanced Structure under Explosion of Mass Ammunition

An advanced structure containing cavities is adopted in distribution layers. A series of large-scale similarity-simulation tests are carried out on defense effect of the four structures for mass ammunition, and numerical simulations are developed by LS-DYNA software. The results indicate that the stress peak is distinctively decayed behind the cavities, and the defense effect of circular-section cavity is more effective than that of rectangle-section cavity. But because the transmission coefficient of stress waves of the structure increases, the defense effect is weakened when a thin steel plate is laid above the cavities.     

Rehabilitation project of the Dabanshan highland road tunnel

The rehabilitation project of road tunnel in highland area and cold region is an important and worthy exploring research field. The development of the defects of crack in the liner, water leakage, structural deterioration and frost defects for Dabanshan road tunnel are studied. After an insight into the cause and development of tunnel defects, the water leakage and frost damage are considered as the root of defect, so restoration of drainage system and the reinstallation of cold prevention system are the focuses of the rehabilitation project. For consideration of safety, cover arch is installed for the tunnel structure enforcement as well. Results indicate measures in Dabanshan road tunnel rehabilitation project are effective for road tunnel of high altitude and tunnel in cold region.     

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.     

FEM analysis on the earth pressure behind the panel of post-panel retaining wall

the distribution of earth pressure behind the panel of post-panel retaining wall is analyzed with 3-D FEM. Eight-crunode isoparametric element is adopted, concrete is regarded as linear elastic object, soil is regarded as elastic-plastic object, an interface model is introduced to simulate the interaction between concrete and soil.It is demonstrated that the earth pressure behind the panel of post-panel retaining wall is greatly different from the classical earth pressure theory, its distribution is close to a parabola. Based on FEM analysis, a modified formula is induced to calculate the earth pressure behind the panel of post-panel retaining wall, the engineering design by this modified formula will be more economical and reasonable.     

Numerical Analysis of Acoustic Environment with Finite Element Method

The acoustic environment of highway tunnel is complex and has influences on the driving safety and comfort. In case of emergency, evacuation information is difficult to transfer. Finite element method is used for calculating highway tunnel acoustic modal and attenuation characteristics. The results show that acoustic mode of highway tunnel has symmetry in the horizontal pressure amplitude of symmetry regional is equal and phase is the same or opposite. The higher modal frequency, the greater sound pressure amplitude is, and the effect of tunnel length on modal frequency is smaller. Decay curves of pressure level at each point in the highway tunnel over time are nonlinear. After the source excitation, in 1.5 s, attenuation rate is faster than that of few seconds later and the attenuation time of sound pressure level 30 dB is 5.5 to 7 s.     

Analysis and Simulation of the Highway Tunnel Fire Contamination

A one-dimensional contamination diffusion model for tunnel fire is presented. Based on this model, a highway tunnel fire within a short time course was simulated and analyzed. Compared to the test results, the simulation result demonstrates that the model is feasible. In the end, it suggests a formula for highway tunnel fire contamination. The author hopes that this analysis will be available as the foundation of highway tunnel fire control.