Abstract: To investigate the mechanical characteristics of horizontal jet grouting arch shed in waterrich sandy stratum affected by tunnel excavation and groundwater, model tests are carried out for three groups of horizontal jet grouting arch sheds with various pile center distances under various excavation footage and groundwater level conditions, and the variation laws of surface settlement, deflection, bending moment, axial force of arch shed, and contact pressure between arch shed and stratum are examined. The results show the following: (1) When the pile center distance is small, the ground settlement, longitudinal axial force and bending moment of the pile, deformation of surrounding strata and the pile are less affected by the tunnel excavation and water level conditions, but the longitudinal compression area of the pile increases. (2) With the increase of the bite thickness between piles, the affected area of the stratum moves forward along the tunnel excavation direction; when the pile center distance is less than 350 mm (that is, the bite thickness between piles continues to increase), the disturbed area of the stratum along the tunnel excavation direction will not change under the support of the horizontal jet grouting arch shed. (3) The groundwater has a great impact on the longitudinal deflection of the arch shed; in the waterrich sandy stratum, increasing the bite thickness between piles(that is, reducing the pile center distance) can effectively reduce the deflection of the arch shed near the excavation surface.

Key words: waterrich sandy stratum, horizontal jet grouting arch shed, mechanical properties, model test, pile center distance