The study investigates the impact of dynamic wave propagation on the dynamic response of two unsupported closely spaced tunnels surrounded by jointed rock mass, using the distinct element method in the time domain. The responses of the tunnels were analysed considering two key factors: the spacing distance between the tunnels (S/D ratio, where S is the spacing and D is the tunnel diameter) and joint density (P32), which is defined as the total fracture area per unit volume. Discrete Fracture Network (DFN) was utilised to simulate weakness zones, which allowed a realistic depiction of the heterogeneous and anisotropic nature of jointed rock masses. The model domain for this study was taken as 80 m × 20 m × 400 m in X-Y-Z directions, incorporating a DFN interlay at the centre. Intact rock and joints were represented by the Hoek–Brown strength criteria and a simple continuous yielding model, respectively. A free-field grid with viscous dashpots at the inner boundary created a ‘quiet’ boundary, allowing unbalanced forces to transfer to the main grid at the outer boundary. A sinusoidal wave of 10 Hz is applied at the bottom of the model. Proximity to joints induces localised stress concentrations, significantly impacting stability both tunnels, especially under dynamic loads, increasing the risk of rock block detachment. Numerical results emphasised dynamic response amplification, particularly at the tunnel walls. Higher joint density (P32 = 0.5 m2/m3) resulted in substantial deformation, with a maximum displacement of 275 mm at an S/D ratio of 0.5. Increasing the spacing to 2D reduced displacements by approximately 67%, with maximum displacement decreasing to 90 mm. For lower joint density (P32 = 0.1 m2/m3), displacements were significantly smaller, reducing from 128 mm at S/D = 0.5 to 57 mm at S/D = 2. These findings emphasise the importance of increasing tunnel spacing to mitigate displacement, ensuring structural stability and safety under dynamic loading conditions.