This idea came from reading this article on the effects of low-yield nuclear weapons. The blast radius of a conventional bomb is roughly proportional to the cubic root of yield, since the energy is deposited in every direction along a spherical front.

One way to enhance the blast radius would be to take inspiration from the nuclear shaped charges designed in the 1960s for the projects Orion (space propulsion) and Casaba-Howitzer (ICBM interception). This variant has a annular configuration to direct blast horizontally all around it.