Page 60 - JSOM Winter 2022

Results FIGURE 1 Comparison of data collections 1 (heavy), 2 (25-grain,
50-grain charges), and 3 hockey puck–style (HP).
Hypothesis 1 was evaluated by recording breach success per
charge. The success rate of untamped and tamped charges for Summary of PSI as Measured from Charge
heavy breaching was 100%, whereas that of the untamped 25 26 ft from 11 ft from charge
charges for light breaching applications was 50% and that of 20 charge
the tamped was 100%. There were two unsuccessful breaches:
one untamped 25-grain charge (door hung improperly) and PSI 15
one untamped 50-grain charge. As previously mentioned, all 10
charges in this phase used a rubber push, with the explosive
secured to the push for best effect. 5
0
Hypothesis 2 considered to what extent, if any, water tamping HP1 HP2 HP3 Heavy 25 gr Linear 50 gr Linear
reduces measured blast overpressure. Water tamping effectively Chart Type
reduced overpressure for all charge levels. On average, water Untamped Tamped
tamping produced an 18.4% overpressure reduction (Table 1).
Note: Because of charge setup, training environment, and other fac-
tors, sensor distance is marked between charges. The most important
Data from site 3 further illustrates that tamping reduces over- factor is that tamping consistently lowered overpressure across setups.
pressure compared with untamped charges (Figure 1). Tamp- PSI, pounds per square inch.
ing conducted in a quasi-enclosed environment consistently
yielded lower overpressure readings compared with untamped because of the increased effectiveness, with the decrease in
charges in study scenarios involving a direct comparison be- pressure being an additional benefit. It cannot be ignored that
tween untamped and tamped charges with equal NEWs and water is heavy, and austere environments may limit the ability
compared with two different NEWs. of personnel to use water-tamped charges. Water alone cannot
replace an effective skill set in breaching without using tamp-
ing materials.
Conclusions, Implications, Limitations,
and Future Directions
This study is limited by its sample size and environment. By
Notably, evaluating all data collections together, the trend attaching to training events, our ability to collect extremely
indicates a reduction of measured overpressure regardless of controlled data was limited. Individual breachers are known
distance to charge, charge construction type, environment, or to have minor variations in charge construction to facilitate
NEW; tamping had a measurable impact in lowering overpres- adaptation to local materials or regional building codes or
sure. What is clear is that there does not appear to be a down- to suit personal preferences in blast outcomes (i.e., tying in
side to tamping with water when conditions allow for it. A a longer tail to kick a door in a specific direction). We feel
positive outcome is reducing Operator exposure to overpres- this is accounted for by evaluating charges from multiple sites
sure, especially in such areas as interior breaching and other across multiple charge builders, demonstrating that the effect
conditions that expose the Operators to reflective pressures of tamping is actually consistent at lowering overpressure on
and increased durations. Reduced overpressure allows Opera- Operators while increasing charge efficacy, despite those vari-
tors to stage closer to explosives and lowers the potential for ations in personal charge building.
compromised reaction time. It also reduces the likelihood of
negative consequences that can result from excessive overpres- Future studies are planned to investigate tamping mediums be-
sure exposure and allows Operators to “do more with less” in yond water (to include gels and fluids with various viscosities),
complex environments where resource access may be limited environment changes (e.g., breaching in fully enclosed/subter-
by logistic or other limitations. ranean spaces), and whether tamping can be used to mitigate
acoustic insult. Additionally, and finally, more explosive types
Water tamping helps mitigate risk to breachers in terms of will also be investigated to determine how explosive velocity
experienced overpressure. Tamping usefully increased breach- interacts with tamping mediums.
ing effectiveness in defeating barriers. Water appears to be a
cost-effective, blast-overpressure mitigation strategy as well as Disclaimer
a strategy for improving the chances of successfully breaching The opinions and assertions contained herein are the private
obstacles to be used by breachers as operational demands dic- views of the authors and are not to be construed as official.
tate. It does, however, seem best to use tamping on all charges This work has been assessed and approved for public release.

TABLE 1 Charge Weight, Type, and Overpressure
95% CI
% Change
Charge Weight Tamped/Untamped n* Mean SD Lower Bound Upper Bound from Untamped
Heavy Untamped 3 3.47 0.35 2.61 4.34 —
Tamped 3 2.83 0.19 2.34 3.31 –18.4
25gr Untamped 2 2.75 0.28 2.31 3.19 —
Tamped 1 2.39 — 1.53 4.10 –13.1
50gr Untamped 2 2.81 0.73 0.99 4.63 —
Tamped 3 2.14 0.65 0.53 3.76 –23.8
*For 25-grain (25gr) and 50-grain (50gr) charges, n represents the number of charges detonated. For the heavy charges, n represents the rows of
sensors in the field.

58 | JSOM Volume 22, Edition 4 / Winter 2022