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Buried charges pose a serious threat to both civilians and military personnel. It is well established that soil properties have a large influence on the magnitude and variability of loading from explosive blasts in buried conditions. In this study, work has been undertaken to improve techniques for processing pressure data from discrete measurement apparatus; this is performed through the testing of truncation methodologies and the area integration of impulses, accounting for the particle size distribution (PSD) of the soils used in testing. Two experimental techniques have been investigated to allow for a comparison between a global impulse capture method and an area-integration procedure from a Hopkinson Pressure Bar array. This paper explores an area-limiting approach, based on particle size distribution, as a possible approach to derive a better representation of the loading on the plate, thus demonstrating that the spatial distribution of loading over a target can be related to the PSD of the confining material.

Buried charges pose a serious threat to both civilians and military personnel. It is well established that soil properties have a large influence on the magnitude and variability of loading from explosive blasts in buried conditions. In this study, work has been undertaken to improve techniques for processing pressure data from discrete measurement apparatus; this is performed through the testing of truncation methodologies and the area integration of impulses, accounting for the particle size distribution (PSD) of the soils used in testing. Two experimental techniques have been investigated to allow for a comparison between a global impulse capture method and an area-integration procedure from a Hopkinson Pressure Bar array. This paper explores an area-limiting approach, based on particle size distribution, as a possible approach to derive a better representation of the loading on the plate, thus demonstrating that the spatial distribution of loading over a target can be related to the PSD of the confining material. [ABSTRACT FROM AUTHOR]

Highlights • Repeat small scale flying plate test with soil blast over two plate sizes. • Soil characterisation for a sandy gravel soil. • Development of an FHWA soil material model. • Numerical validation and analysis using LS-DYNA. Abstract This paper presents the results of a combined experimental and numerical investigation into the blast loading generated by an explosive charge buried in an unsaturated soil. The dynamic response of the soil blast is quantified by its impulse imparted onto a high strength steel plate in a flying plate experiment. A 50 mm-thick plate of exposed area 500 mm by 500 mm is located at a constant stand-off distance of 400 mm above the surface of the soil. Upon detonation, the plate's heights are recorded and analysed using the initial velocity of the plate calculated from the flying time, while the rotation of the plates was shown to have negligible influence. Detailed unsaturated soil preparation, in-situ and laboratory characterisation as well as experimental setup are reported and compared to obtained meaningful parameters of the soil for the tests. The numerical model for the soil blast impact on the steel plates is developed based on the Arbitrary Lagrangian-Eulerian (ALE) method in the commercial simulation package LS-DYNA. Key soil properties, such as density, moisture content, bulk and shear moduli are characterised and utilised as input parameters into the FHWA material model in the numerical model. Results from a series of soil blast tests with 0.5 kg TNT charges on different plate sizes are presented and validated numerically. The numerical models agree generally well with the unsaturated soil blast test results, while the observed variations in the plate height are clearly attributed to the sensitivity of the soil properties. [ABSTRACT FROM AUTHOR]

Experiments have been conducted to quantify the effect the geotechnical conditions surrounding a buried charge have on the resulting output. From the results obtained the critical importance of moisture content in governing the magnitude of impulse delivered is highlighted. This has led to the development of a first-order predictive model for the impulse delivered from a buried charge, based on bulk density and moisture content, allowing rapid assessment of the effect of varying the geotechnical conditions. The work utilised a half-scale impulse measurement apparatus which incorporated a deformable target plate. Impulse, peak and residual target deflections were recorded for each test. No variations the charge geometry, mass of explosive, burial depth or stand-off were considered, with the focus solely being on the effect of the geotechnical conditions on the magnitude of loading and structural response. Five different types or grades of soils were used in the work, with both cohesive and cohesionless soils represented. The effect of air voids on the impulse generated was also investigated which showed that while strongly correlated, air voids alone is a poorer predictor of impulse than moisture content. [ABSTRACT FROM AUTHOR]

The role of the geotechnical conditions on the impulse delivered by a shallow buried charge has received much attention in recent times. As the importance of the soil in these events has become better understood, the control over the geotechnical conditions has improved. While previous work has investigated directly the role of geotechnical conditions on the magnitude of the impulse from a buried charge, the current work aims to identify how these same conditions also affect the repeatability of testing using soils. In this paper the authors draw together their work to date for a wide range of different soil types and moisture contents to investigate the variation in output from nominally identical tests. The methodology for the preparation of soil beds and the measurement of impulse is described along with the measured variations in peak and residual deflections of a target plate fixed to the impulse measurement apparatus. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of an experimental investigation to determine the effect of the height of burial (the amount of sand beneath the buried charge) on a buried charge in terms of impulses imparted onto a rigid steel target plate (suspended from a vertical pendulum). The 40 mm rigid target plate of exposed area 400 mm × 400 mm is located at a constant stand-off distance of 47 mm above the surface of the sand. Tests conducted at a height of burial of 0 mm (placed flush on a steel base plate) resulted in the largest impulse transfer for all depth of burial (amount of sand above the buried charge) values tested. The optimal depth of burial for impulse transfer was observed to occur within 50–70 mm irrespective of the height of burial (0–110 mm). Semi-infinite height of burial conditions are attained when any further increase in the height of burial does not influence the impulse transfer to the target plate. The height of burial representing semi-infinite conditions observed in the experiments is a function of the depth of burial. [Copyright &y& Elsevier]

Abstract: This paper presents experimental and numerical results of an investigation to determine the response of quadrangular steel plates subjected to explosive charges buried under dry construction sand. The buried charges were designed to simulate a landmine blast. Three parameters; depth of burial, stand-off distance and mass of explosive, were varied to provide a range of impulsive loads and plate responses. A vertical ballistic pendulum was used to measure the impulse imparted from the buried charges onto the deformable or rigid target plates. The results showed that as the depth of burial increases the impulse imparted onto the plate increases. The midpoint deflection of the plate reaches a maximum, after which the deflection decreases with a continual increase in depth of burial. The numerical model, developed in ANSYS AUTODYN R12.1a and validated against the experiments, provided insight into the transient response of both the plates and the sand. The numerical models indicated that for most of the tested stand-off distances the sand did not impact the plate as an ejecta but as a sand dome with complete containment of the detonation products. The sand serves to focus the high pressure and high temperature detonation products onto the plate. This focussing effect increases with the depth of burial. The plate deformation is dependent on the amount of energy the sand can absorb (via compaction) which is directly proportional to the depth of burial. [Copyright &y& Elsevier]

Ionizable residues play essential roles in proteins, modulating protein stability, fold and function. Asp, Glu, Arg, and Lys make up about a quarter of the residues in an average protein. Multi-conformation continuum electrostatic (MCCE) calculations were used to predict the ionization states of all acidic and basic residues in 490 proteins. Of all 36,192 ionizable residues, 93.5% were predicted to be ionized. Thirtyfive percent have lost 4.08kcal/mol solvation energy (ΔΔG rxn) sufficient to shift a pK a by three pH units in the absence of other interactions and 17% have ΔΔG rxn sufficient to shift pK a by five pH units. Overall 85% of these buried residues (ΔΔG rxn>5ΔpK units) are ionized, including 92% of the Arg, 86% of the Asp, 77% of the Glu, and 75% of the Lys. Ion-pair interactions stabilize the ionization of both acids and bases. The backbone dipoles stabilize anions more than cations. The interactions with polar side-chains are also different for acids and bases. Asn and Gln stabilize all charges, Ser and Thr stabilize only acids while Tyr rarely stabilize Lys. Thus, hydroxyls are better hydrogen bond donors than acceptors. Buried ionized residues are more likely to be conserved than those on the surface. There are 3.95 residues buried per 100 residues in an average protein. [Copyright &y& Elsevier]

• Structural deformations of Armox 440 steel plates from explosive charges measured. • Repeatable test methods described. • Different methods of measuring dynamic deformation compared. • Relationship between charge weight, plate thickness and deformation level defined to allow comparison with other armour designs. • Relationship between dynamic deformation and final plastic deformation measured. Loading of vehicle undercarriages from the detonation of shallow-buried explosives remains a serious threat to life in conflict and post-conflict zones. One method to protect lightly-armoured vehicles is to retrofit them with appliqué armour, which must be strong enough to provide adequate protection, but light enough to maintain vehicle manoeuvrability. A key performance metric of this armour is its deformation under loading, which must be limited to avoid impact upon vehicle occupants. The high-strength steel Armox 440T is commonly used due to its high load capacity, strength-to-weight ratio, ductility and low cost: as other protection systems are developed, it would be of great benefit to compare their deformation against an Armox 440T benchmark. However, no definitive benchmarking study has been published to date, mainly due to the difficulties in ensuring repeatable loading from complex buried detonations. This paper presents experiments which underpin such a benchmarking study, building on the authors' previous work to establish a methodology which produces very consistent loading from shallow-buried detonations. Tests were conducted with a range of explosive masses and plate thicknesses, with target plates secured in a purpose-designed frame to produce simple, consistent boundary conditions. Plate deformations captured by stereo high-speed digital image correlation were compared to a commonly-used low-cost peak deflection method. High-speed digital image correlation was found to make highly reproducible displacement measurements with a standard deviation of 2% of the mean. The low-cost method provided slightly higher variability up to 5% of the mean value, and measurements of peak deformation were systematically 20% higher, but in a consistent manner, with a low unit cost and without risk to expensive test equipment. The low-cost method therefore allowed the development of a multivariate regression relationship between deformation, charge size and plate thickness, which provides a benchmark for the assessment of future protection solutions. [ABSTRACT FROM AUTHOR]