We simulated the Defense Threat Reduction Agency (DTRA)-sponsored Jointed Limestone Test (JOLT) using the Abaqus fully coupled Euler-Lagrange computation scheme. JOLT was a small-scale experiment consisting of over 37,000 individual cubes of limestone surrounding simulated tunnels. This test bed was loaded with ground shock generated by a spherical CompB charge, thereby providing data for the study of computer codes used to compute the response of buried tunnels to explosive loading. We modeled the cubes as continuum blocks with contact, making for a dis-continuum simulation using a hybrid continuum code including Eulerian modeling of the explosive region and Lagrangian modeling of the remainder of the test bed. This paper has been approved for unlimited release under LA-UR-15-21382.
The Defense Threat Reduction Agency (DTRA) has funded studies of tunnel vulnerability to blast effects for decades. The studies have included experiments of various complexity and scale as well as numerical analysis. Several projects have combined computational studies with experiments to validate predictive algorithms. Numerical approaches have evolved based not only on prior knowledge but also due to advances in computing hardware and software capabilities. The focus of this paper is on a recent three-dimensional (3-D) simulation effort, but we will also provide some background material by describing an older twodimensional (2-D) computational effort that laid some of the groundwork for this later work
2. MIGHTY NORTH
The MIGHTY NORTH event was a laboratory-scale high explosive test performed in the mid-90s to investigate various approaches to numerical simulation of the response of tunnels to explosive-induced ground shock [1, 2]. The test bed (Figure 1) consisted of 1.2-m long, 5-cm square cross-section bars of limestone stacked in an imbricate pattern to simulate a layered, jointed geologic setting. The "block of bricks" was 2 m square in section and 2 m long. The center of the block included a 0.4-m diameter aluminum-lined "tunnel."