<p>Filling the medium between the blast hole and the explosive can regulate the release of the explosion energy. The spatio-temporal evolution characteristics of the explosion strain field and crack field in the radially uncoupled medium, as well as the energy distribution mechanism, are analyzed by theoretical derivation and in combination with the dynamic caustic line and DIC experimental system. The results indicated that: The horizontal peak strain of water, sand, and plasticine in decoupled blasting is 3.7, 2.5, and 2.2 times that of air, respectively, and the vertical peak strain is 3.5, 2.8, and 2.3 times that of air, respectively. The Von Mises strain is 3.0, 2.3, and 2.0 times that of air, respectively. The radius of the crack zone is 2.55, 2.26, and 0.69 times that of air, respectively. The peak crack propagation speed of water and sand in decoupled blasting is 2.5 times that of air and plasticine. The peak stress intensity factor is 64.6% and 20.1% higher than that of air, respectively, while that of plasticine is 18.5% lower than that of air. The fractal dimension of the crack field is 20.5% and 11.9% higher than that of air, respectively, while that of plasticine is 6.2% lower than that of air. The fractal dimension of the fragmentation zone and the inner and outer crack zones in water decoupled blasting is 8.2%, 15.0%, and 38.7% higher than that of air, respectively, while that of sand is 6.3%, 8.4%, and 31.1% higher than that of air, respectively, and that of plasticine is 10.8%, 9.2%, and 35.7% lower than that of air, respectively. The trade-off between “peak strain” and “continuous energy action” in the blasting crack and the decisive influence of the physical properties of the decoupled medium on the energy distribution are clarified.</p>