During the tunnel construction process using the drilling and blasting method, the induced blasting vibration always poses a great threat to the stability and safety of the adjacent tunnel supporting structure. To improve the efficiency and safety of tunnel blasting construction, the vibration propagation and peak particle velocity (PPV) distribution of the lining of an excavated tunnel were investigated during the blasting of an adjacent tunnel located in Guangxi province. The evolution process and distribution characteristics of the PPV of the lining of adjacent tunnels were monitored and analyzed. The results show that the maximum blasting vibration velocity of the lining of the adjacent tunnel can be shown as: PPVx > PPVz > PPVy; hence, the PPVx plays a significant role in the vibration of the adjacent tunnel. According to the tensile stress failure criterion, the PPV threshold was determined to be 12.7 cm/s in this study. To control the damage of surrounding rock induced by the blasting vibration, compound wedge-shaped cutting technology, stress wave dislocation superposition technology, and pre-splitting blasting technology were employed to reduce the impact of blasting vibration on the excavated tunnel.

To investigate the effect of oyster shell powder (OSP) on the static and dynamic properties of expansive soil, the mechanical properties of modified soil were obtained. Taking Ningming expansive soil as the research object, triaxial shear test, dynamic triaxial test and scanning electron microscope test were carried out on plain soil and 9 % expansive soil modified by oyster shell powder (ESMO). The results show that compared with plain soil, the effective cohesion of modified expansive soil with d_osp < 1 mm (ESMO (d_osp < 1 mm)) and d_osp < 0.075 mm (ESMO (d_osp < 0.075 mm)) is increased by 15.4 % and 32.8 %, respectively. Under cyclic loading, compared with plain soil, the plastic strain stability value of ESMO (d_osp<0.075 mm) is reduced by 40.2 %, the pore water pressure stability value is reduced, and the stiffness is increased. The dynamic mechanical properties of ESMO (d_osp<1 mm) showed the opposite trend. Through microscopic experimental analysis, the main reasons for this phenomenon are the particle size distribution, bonding form, and cementation of the two. The results can provide a theoretical basis for the practical application of ESMO and the establishment of constitutive model.