In-Tunnel Blast Pressure Empirical Formulas for Detonations External, Internal and at the Tunnel Entrance

In order to define the loading on protective doors of an underground tunnel, the exact knowledge of the blast propagation through tunnels is needed. Thirty-three scale high-explosive tests are conducted to obtain in-tunnel blast pressure for detonations external, internal and at the tunnel entrance. The cross section of the concrete model tunnel is 0.67 m2. Explosive charges of TNT, ranging in mass from 400 g to 4 600 g, are detonated at various positions along the central axis of the model tunnel. Blast gages are flush-installed in the interior surface of the tunnel to record side-on blast pressure as it propagates down the tunnel. The engineering empirical formulas for predicting blast peak pressure are evaluated, and are found to be reasonably accurate for in-tunnel pressure prediction.     

Dynamic Responses Analysis of a Building Structure Subjected to Ground Shock from a Tunnel Explosion

Dynamic responses of a multi-storey building without or with a sliding base-isolation device for ground shock induced by an in-tunnel explosion are numerically analyzed. The effect of an adjacent tunnel in between the building and the explosion tunnel, which affects ground shock propagation, is considered in the analysis. Different modeling methods, such as the eight-node equal-parametric finite element and mass-lumped system, are used to establish the coupling model consisting of the two adjacent tunnels, the surrounding soil medium with the Lysmer viscous boundary condition, and the multi-storey building with or without the sliding base-isolation device. In numerical calculations, a continuous friction model, which is different from the traditional Coulomb friction model, is adopted to improve the computational efficiency and reduce the accumulated errors. Some example analyses are subsequently performed to study the response characteristics of the building and the sliding base-isolation device to ground shock. The effect of the adjacent tunnel in between the building and the explosion tunnel on the ground shock wave propagation is also investigated. T.he final conclusions based on the numerical results will provide some guidance in engineering practice.     

Analysis of blast wave propagation inside tunnel

The explosion inside tunnel would generate blast wave which transmits through the longitudinal tunnel. Because of the close-in effects of the tunnel and the reflection by the confining tunnel structure, blast wave propagation inside tunnel is distinguished from that in air. When the explosion happens inside tunnel, the overpressure peak is higher than that of explosion happening in air. The continuance time of the blast wave also becomes longer. With the help of the numerical simulation finite element software LS-DYNA, a three-dimensional nonlinear dynamic simulation analysis for an explosion experiment inside tunnel was carried out. LS-DYNA is a fully integrated analysis program specifically designed for nonlinear dynamics and large strain problems. Compared with the experimental results, the simulation results have made the material parameters of numerical simulation model available. By using the model and the same material parameters, many results were adopted by calculating the model under different TNT explosion dynamites. Then the method of dimensional analysis was used for the simulation results. As overpressures of the explosion blast wave are the governing factor in the tunnel responses, a formula for the explosion blast wave over-pressure at a certain distance from the detonation center point inside the tunnel was derived by using the dimensional analysis theory. By comparing the results computed by the formula with experimental results which were obtained before, the formula was proved to be very applicable at some instance. The research may be helpful to estimate rapidly the effect of internal explosion of tunnel on the structure.     

Dynamic Responses Analysis of a Building Structure Subjected to Ground Shock from a Tunnel Explosion

Dynamic responses of a multi-storey building without or with a sliding base-isolation device for ground shock induced by an in-tunnel explosion are numerically analyzed. The effect of an adjacent tunnel in between the building and the explosion tunnel, which affects ground shock propagation , is considered in the analysis. Different modeling methods, such as the eight-node equal-parametric finite element and mass-lumped system, are used to establish the coupling model consisting of the two adjacent tunnels, the surrounding soil medium with the Lysmer viscous boundary condition, and the multi-storey building with or without the sliding base-isolation device. In numerical calculations , a continuous friction model, which is different from the traditional Coulomb friction model, is adopted to improve the computational efficiency and reduce the accumulated errors. Some example analyses are subsequently performed to study the response characteristics of the building and the sliding base-isolation device to ground shock. The effect of the adjacent tunnel in between the building and the explosion tunnel on the ground shock wave propagation is also investigated. The final conclusions based on the numerical results will provide some guidance in engineering practice.     

高炉TRT控制系统模型仿真研究

根据高炉TRT工艺和影响高炉顶压稳定的因素,以及对高炉TRT系统的管路分析,建立高炉顶压TRT系统数学模型。应用Matlab对静叶单独调节高炉顶压时系统的数学模型进行仿真验证,为进一步改善高炉顶压的稳定提供理论依据。     

Analysis of structural response under blast loads using the coupled SPH-FEM approach

A numerical model using the coupled smoothed panicle hydrodynamics-finite element method （SPH-FEM） approach is presented for analysis of structures under blast loads. The analyses on two numerical cases, one for free field explosive and the other for structural response under blast loads, are performed to model the whole processes from the propagation of the pressure wave to the response of structures. Based on the simulation, it is concluded that this model can be used for reasonably accurate explosive analysis of structures. The resulting information would be valuable for protecting structures under blast loads.     

Retrofitting of RC Slabs Against Explosive Loads

With the increase of terrorist bomb attacks on buildings, there is a need to develop advanced retrofitting techniques to strengthen structures against blast loads. Currently, several guidelines including an Australian version for retrofitting reinforced concrete (RC) structures are available for the design of retrofitting systems against seismic and monotonic loads using steel or fibre reinforced polymer (FRP) plates that can be either adhesively bonded to the surface or near surface mounted to the concrete cover. However, none of these guidelines provide advice suitable for retrofitting structures subjected to blast loads. In this paper, numerical models are used to simulate the performance of retrofitted RC slabs subjected to blast loads. Airblast pressure distributions on the surface of the slabs estimated in a previous study are used as input in the analysis. A material damage model developed previously for concrete and an elastoplastic model for steel bars are employed in this research for modelling reinforced concrete behaviour due to explosive loads. The material models and blast loading are coded into a finite element computer program LS-DYNA3D to do the analysis. With the numerical model, parametric studies are conducted to investigate RC slabs retrofitted by either externally bonded or near-surface mounted plates or GFRP sheets subjected to blast loads. Discussion is made on the effectiveness of the retrofitting system for RC slabs against blast loads.     

Unsteady simulation for a high-speed train entering a tunnel

In order to study the unsteady aerodynamics effects in railway tunnels, the 3D Reynolds average Navier-Stokes equations of a viscous compressible fluid are solved, and the two-equation k-? model is used in the simulation of turbulence, while the dynamic grid technique is employed for moving bodies. We focus on obtaining the changing tendencies of the aerodynamic force of the train and the aerodynamic pressures on the tunnel wall and train surface, and discovering the relationship between the velocity of the train and the intensity of the micro pressure wave at the tunnel exit. It is shown that the amplitudes of the pressure changes in the tunnel and on the train surface are both approximately proportional to the square of the train speed, so are the microwave and the drag of the train.     

盾构施工参数对地层变形的影响

以南宁地铁一号线南湖段下穿隧道为工程背景,建立隧道开挖的三维有限元模型,通过数值分析,得到盾构施工过程中地层变形的分布规律,讨论盾构施工过程中注浆压力对地表沉降、水平位移及拱顶位移的影响,分析掌子面压力对地表隆起的影响规律。研究结果表明,注浆压力对地表变形会产生明显的影响,随着注浆压力的增大,地表沉降及水平位移明显减小。当掌子面压力大于0.1 MPa时,会引起掌子面前方土体产生向上的位移,地表隆起量随掌子面压力的增加而增大。     

架棚巷道支护结构的分析与探讨

通过架棚巷道支护结构分析,架棚巷道破坏原因多是由于巷道的侧压力和底鼓引起,造成棚子相对下沉,使巷道变形、断面变小,采取在巷道两墙打锚杆和棚脚穿钢筋混凝土鞋后巷道围岩对侧压力减小了,支架支承能力增强,提高了巷道的稳定性。     

挡墙对爆炸冲击波传播影响的三维数值模拟

采用有限元软件AutoDyn,对TNT炸药起爆后爆炸冲击波遇到挡墙时的传播规律进行了三维数值模拟,分析了冲击波遇到挡墙时的反射高压及冲击波的环流汇聚作用。结果表明：冲击波遇到挡墙时将会产生反射高压;在比距离较小时,挡墙迎爆面的最大压力发生在挡墙底部;而随着比距离的增大,压力分布将沿挡墙高度趋于均匀。由于反射的作用,在挡墙前的地面上将会出现高压;当冲击波绕过挡墙时,在冲击波三个方向的绕射汇聚作用下,将会在墙后面一定区域内突然产生局部高压,并且随着传播的继续,这个区域不断的扩大,最后再次形成球面波传播。     

Numerical Modeling of Response and Damage of Masonry Walls to Blast Loading

To model the damage process of masonry walls under blast loading, a dynamic continuum damage material model is constructed for brick and mortar separately. The degradation of both the stiffness and strength are governed by a damage variable. By using the proposed material model, damage and fragmentation of a typical masonry wall under blast loading at different scaled distances is calculated. The hazard level of the masonry wall to blast loading is evaluated by analyzing the numerical results.     

Numerical Modeling of Response and Damage of Masonry Walls to Blast Loading

To model the damage process of masonry walls under blast loading, a dynamic continuum damage material model is constructed for brick and mortar separately. The degradation of both the stiffness and strength are governed by a damage variable. By using the proposed material model, damage and fragmentation of a typical masonry wall under blast loading at different scaled distances is calculated. The hazard level of the masonry wall to blast loading is evaluated by analyzing the numerical results.     

BP神经网络PID控制在高炉TRT顶压控制系统中的仿真

为改善传统PID的控制缺陷,提出了BP神经网络PID控制算法应用于高炉TRT顶压控制系统中的设计构想,并针对影响高炉炉顶压力稳定的两个重要参数,运用Matlab软件进行仿真,结果表明,该优化控制算法对高炉顶压控制系统的控制效果明显优于传统PID。     

Mitigation of Blast Effects on Aluminum Foam Protected Masonry Walls

Terrorist attacks using improvised explosive devices (lED) can result in unreinforced masonry (URM) wall collapse.Protecting URM wall from lED attack is very complicated.An effective solution to mitigate blast effects on URM wall is to retrofit URM walls with metallic foam sheets to absorb blast energy.However,mitigation of blast effects on metallic foam protected URM walls is currently in their infancy in the world.In this palaer,numerical models are used to simulate the performance of aluminum foam protected URM walls subjected to blast loads.A distinctive model,in which mortar and brick units of masonry are discritized individually,is used to model the performance of masonry and the contact between the masonry and steel face-sheet of aluminum foam is modelled using the interface element model.The aluminum foam is modelled by a nonlinear elastoplastic material model.The material models for masonry,aluminum foam and interface are then coded into a finite element program LS-DYNA3D to perform the numerical calculations of response and damage of aluminum foam protected URM walls under airblast loads.Discussion is made on the effectiveness of the aluminum foam protected system for URM wall against blast loads.     

Discontinuum analyses of openings constructed with side drift and limited rock cover

The design of rock support for a typical horseshoe shaped tunnel with considerations of it being excavated into a twin arch tunnel was studied using the distinct element method (DEM). Two different competent rock covers, i.e. 4 m and 7.5 m above the tunnel crown, were analysed. The results are relevant to the granitic geological unit in Singapore which has a weathering profile with rockhead found at some locations to be only 20–35 m below ground level and undulating, leaving limited rock cover for some sections along tunnels of similar depth. The verification of the adequacy of competent rock cover is important to ensure that the choice of ground support is suitable, particularly when the tunnel is excavated using the drill-and-blast method. In the opening geometry analysed in this study, a side drift is excavated adjacent to the first tunnel to create a twin arch opening. This creates a pillar between the openings during the intermediate construction stage. The influence of excavating the side drift on the support of the first opening was studied. We found that the bolt forces in the pillar approximately doubled during the excavation of the side drift, which may have been due to the rock joint inclinations and adopted strength parameters. This paper shows how DEM analyses may be used to complement conventional empirical rock mass classifications to design rock supports. Limitations of the pressure relaxation approach to model 3D effects in 2D are acknowledged.     

Mitigation of Blast Effects on Aluminum Foam Protected Masonry Walls

Terrorist attacks using improvised explosive devices (IED) can result in unreinforced ma-sonry (URM) wall collapse. Protecting URM wall from IED attack is very complicated. An effective solution to mitigate blast effects on URM wall is to retrofit URM walls with metallic foam sheets to absorb blast energy. However, mitigation of blast effects on metallic foam protected URM walls is currently in their infancy in the world. In this paper, numerical models are used to simulate the per-formance of aluminum foam protected URM walls subjected to blast loads. A distinctive model, in which mortar and brick units of masonry are discritized individually, is used to model the perform-ance of masonry and the contact between the masonry and steel face-sheet of aluminum foam is modelled using the interface element model. The aluminum foam is modelled by a nonlinear elas-toplastic material model. The material models for masonry, aluminum foam and interface are then coded into a finite element program LS-DYNA3D to perform the numerical calculations of response and damage of aluminum foam protected URM walls under airblast loads. Discussion is made on the effectiveness of the aluminum foam protected system for URM wall against blast loads.     

Numerical analysis of dynamic behavior of RC slabs under blast loading

In Order to reduce economic and life losses due to terrorism or accidental explosion threats,reinforced concrete(RC)slabs of buildings need to be designed or retrofitted to resist blast loading.In this paper the dynamic behavior Of RC slabs under blast loading and its influencing factors are studied.The numerical model of an RC slab subjected to blast loading is established using the explicit dynamic analysis software.Both the strain rate effect and the damage accumulation are taken into account in the material model.The dynamic responses of the RC slab subiected to blast loading are analyzed,and the influence of concrete strength,thickness and reinforcement ratio on the behavior of the RC slab under blast loading iS numerically investigated.Based on the numerical results.some principles for blast-resistant design and retrofitting are proposed to improve the behavior of the RC slab subjected to blast loading.     

Numerical Calculation of Concrete Slab Response to Blast Loading

In the present paper, a dynamic plastic damage model for concrete has been employed to estimate responses of a reinforced concrete slab subjected to blast loading. The interaction between the blast wave and the concrete slab is considered in 3D simulation. In the first stage, the initial detonation and blast wave propagation is modelled in 2D simulation before the blast wave reaches the concrete slab, then the results obtained from 2D calculation are remapped to a 3D model. The calculated blast load is compared with that obtained from TM5-1300. Numerical results of the concrete slab response are compared with the explosive test carried out- in the Weapons System Division, Defence Science and Technology Organisation, Department of Defence, Australia.     

Numerical Calculation of Concrete Slab Response to Blast Loading

In the present paper, a dynamic plastic damage model for concrete has been employed to estimate responses of a reinforced concrete slab subjected to blast loading. The interaction between the blast wave and the concrete slab is considered in 3D simulation. In the first stage, the initial detonation and blast wave propagation is modelled in 2D simulation before the blast wave reaches the concrete slab, then the results obtained from 2D calculation are remapped to a 3D model. The calculated blast load is compared with that obtained from TM5-1300. Numerical results of the concrete slab response are compared with the explosive test carried out-in the Weapons System Division, Defence Science and Technology Organisation, Department of Defence, Australia.