There are three paths that you can follow in order to simulate blast actions.

1. Use the empirical model CONWEP (it's implemented in ABAQUS) in a FEA. You would need to define the equivalent TNT mass of explosive, the source point (i.e. where the explosive is located), and the solid surfaces on which the wave font impinges.

2. CEL (Coupled-Eulerian-Lagrangian) simulation. You need to model the eulerian volume of air and explosive, as Reza Saidafkan suggested. So it would be computationally and time expensive, e.g. you need to validate not only the solid "structures" but also the eulerian domain. On the other side, you can take into account for "every" kind of reflection, that would be quite significant in an underground scenario of the kind you're investigating. (if you have time, I suggest you to read "A study on the simulation of blast actions on a monument structure" fom Vannucci et al. it's a state of the art of the different approaches to simulate blast actions);

3. You can simulate the scenario of an explosion through a pressure impulse inside a fluid domain (the air) with a CFD simulation, and then "export" the pressure history acting on the solid surfaces on a FEM analysis, and running a simple explicit FE analysis. 

Good luck.

https://hal.archives-ouvertes.fr/hal-01447783

I suggest you come up with the history of load i.e. a diagram showing how the load varies with time. I suppose that the blast load could be represented either as a pulse or step load that occur over a short period of time. Abaqus should accept time history load and then you can run a time history analysis.

An explosion is a sudden increase in volume that results in an increase of pressure on the surrounding areas around the blast point. In terms of modeling, it could be modeled by a bilinear approach, in other words, by using one ascending line and then another constant line.

Since you are dealing with an underground metro tunnel, your initial surface blast loads need to be adjusted. That is, the magnitude of blast loads that the metro tunnel experiences are less than what is really happening at the surface. This is due to the fact that soil (spreads) the effect of the blast load out. Thus, you must calculate the reduced load that is really acting on the metro tunnel.  To do so, you have two approaches:

1) = HARD = model the soil layers in your FEM program

2) = Easy = Calculate the real loads acting on the metro tunnel (this lets you skip the modeling of soil layers and the complications that arise while doing so. In order to calculate these real loads, please refer to the chapters in soil/foundation mechanics text books dealing with ("Stress distribution in soil due to surface loads")

Best Regards and Uppermost Respects,

MJ

Thank you researchers

Now How I can calculate the load-time curve of TNT blast? could you introduce any reference?

I checked up an MSc thesis. Chapter 2 should be of relevance.

http://www.civ.utoronto.ca/vector/theses/Miller-MASc%282004%29.pdf

Good Luck.

One precise but computationally expensive method for HE blast modeling:

You could calculate the required TNT volume and introduce a corresponding volume to Abaqus in a Eulerian part using "volume fraction tool", and define the detonation time using TNT material properties for JWL EOS using "suboptions" -> "detonation delay time".

Good luck

There are three paths that you can follow in order to simulate blast actions.

1. Use the empirical model CONWEP (it's implemented in ABAQUS) in a FEA. You would need to define the equivalent TNT mass of explosive, the source point (i.e. where the explosive is located), and the solid surfaces on which the wave font impinges.

2. CEL (Coupled-Eulerian-Lagrangian) simulation. You need to model the eulerian volume of air and explosive, as Reza Saidafkan suggested. So it would be computationally and time expensive, e.g. you need to validate not only the solid "structures" but also the eulerian domain. On the other side, you can take into account for "every" kind of reflection, that would be quite significant in an underground scenario of the kind you're investigating. (if you have time, I suggest you to read "A study on the simulation of blast actions on a monument structure" fom Vannucci et al. it's a state of the art of the different approaches to simulate blast actions);

3. You can simulate the scenario of an explosion through a pressure impulse inside a fluid domain (the air) with a CFD simulation, and then "export" the pressure history acting on the solid surfaces on a FEM analysis, and running a simple explicit FE analysis. 

Good luck.

https://hal.archives-ouvertes.fr/hal-01447783

In abaqus, the Conwep Method was limited in use for distance-weight restrained in theory.

if the Scale distance not in accepted region for conwep the result was not true.

so you must be apply some one of:

1-load- time profile

2- use surface blast

3-use CEL

Use of the Coupled Eulerian Lagrangian Simulation will be effective in this regards. Simulating blast loads as pressure time history inputs in the amplitude of force will not be accurate in many cases.

Best Wishes.