Session L6: Particulate, Porous and Composite Mateials IV: Sand

The Effect on the Propagation of Blast Pulses of Dry and Dampened Granular Media

The propagation of stress through granular and dampened granular material has been reported in previous papers. With increasing presence of liquid in granular beds the transmission of blast and pressure pulse changes from one of percolation through the bed pores to one of wave transmission through the granules of the bed. It has been shown that limited amounts liquid can retard pressurisation within confined blast-loaded beds by approximately an order of magnitude. This study presents data on percolation through dry and dampened granular beds using a shock tube as the pressure driver. In this scenario the effect of the bed on initial pressure pulse is studied in greater detail.The effect of particle shape and size was investigated using angular grains of quartz sand as well as smooth glass microspheres. The effect of addition of liquids is presented. The pressure range studied is in the range associated with blast injury and with far field effects produced by explosive devices.   

Dynamic High-Pressure Behavior of Quartz Silica Sand of Two Different Particle Sizes

The dynamic high-pressure behavior of customized high purity quartz silica sand is presented. The silica was chosen to have rounded grains and controlled size, size distribution, and water content. The customized sand was selected with two narrow size ranges, approximately 100$\mu$m and 500$\mu$m, to provide a range of responses to compare with meso-scale simulations. The materials were pressed into a copper capsule ring connected to a copper driver plate and backed by a PMMA window. Experiments were performed in plate impact light gas gun and powder gun, using VISAR and PDV velocity measurement techniques, and PVDF piezoelectric pressure gauges. The compaction wave velocity was calculated from transit times measured by PVDF gauges placed on either side of the silica samples. Interface particle velocity profiles were recorded by VISAR and PDV at the rear surface of the sample in contact with a PMMA window. Analysis of the details of the shapes of the rise and plateaus in the VISAR and PDV measured velocities reveal a dependence on the size of the particles.   

Shock Compression of Simulated Adobe

A series of plate impact experiments were conducted to investigate the shock response of a simulant for adobe, a traditional form of building material widely used around the world. Air dried bricks were sourced from the London brick company, dry machined and impacted at a range of velocities in a single stage gas gun. The shock Hugoniot was determined (U$_{s}=$2.26u$_{p}+$0.33) as well as release information. The material was found to behave in a manner which was similar to that of loose sand and considerably less stiff than a weak porous sandstone. The effect of any cementing of the grains was examined by shocking powdered samples contained within a cell arrangement.   

The shock and release properties of dry and wetted silica sands

While the shock response of dry sand has been studied at length, the Hugoniots for partially and fully wetted silicaceous granular materials are less well understood. Here, we present an extensive experimental plate impact investigation for a well characterized silica sand under dry, moist and water-saturated conditions. Particular attention is paid to cell design and sample preparation. Furthermore, we have applied our technique for measuring both shock Hugoniot and release to vacuum for granular materials, as presented previously, to the wetted systems studied.   

Hugoniot Measurements on Dry and Water-Saturated Soils

To better understand the shock properties of granular materials, we present a series of shock Hugoniot experiments on three types of soil in both dry and water-saturated states. We measured the shock states induced via planar impact experiments on the Harvard 40-mm gas gun. Shock wave velocities in the soils were measured using both VISAR and piezo-pins. The soils were composed primarily of quartz with different mass fractions of phyllosilicates and amorphous material. Using initial particle sizes ranging from 150 to 300 microns, the samples were pressed to densities ranging from 1.89 to 1.93 g cm$^{-3}$ (about 25\% porous). Water-sat samples had densities ranging from 2.2 to 2.6 g cm$^{-3}$. We find that the dry soils have a linear $U_s-u_p$ relation that is similar to dry quartz sand with the same initial density. The water-sat samples are less compressible and have much greater scatter in shock velocities. The VISAR measurement records the dispersion around the mean shock state that arises from reflections between grains, and we compare the VISAR data to meso-scale hydrocode simulations. These data will be used to generate more accurate rheological models for hydrocode simulations of the shock response of heterogeneous granular materials in the low-pressure regime ($<10$ GPa).   

Stress and Temperature Distributions of Individual Particles in a Shock Wave Propagating through Dry and Wet Sand Mixtures

Determining stress and temperature distributions of dynamically compacted particles is of interest to the geophysical and astrological research communities.~ However, these particle interactions during a shock event are not easily observed in planar shock experiments; it is with the utilization of mesoscale simulations that these granular particle interactions can be unraveled. Unlike homogenous materials, the overall averaged hugoniot state for heterogeneous granular materials differs from the individual stress and temperature states of particles during a shock event. ~From planar shock experiments on dry and wet sand mixtures, simulations were constructed using CTH. ~A baseline dry sand simulation was also setup to be compared to sand grains that possessed water particles between grains. It is from these simulations that the distributions of stress and temperatures for individual sand and water particles are presented and compared in this document.~