ASSESSMENT OF GROUND SURFACE FLUCTUATIONS DURING SHIELD TUNNELING OF SUBWAY TUNNELS

Abstract

T The problems of evaluation of ground surface vibrations created by underground vibration sources are quite acute, especially in the conditions of urban development. During the construction of subway tunnels by the shield method there is a dynamic impact during the work of working mechanisms. The oscillations during the excavation of the soil by cutting mechanisms of the shield complex, during the ground bailing and pumping of mortar behind the lining can reach the day surface and cause significant deformations. When designing long underground tunnels built next to existing buildings, it is necessary to estimate the parameters of dynamic impact on the buildings caused by the operation of shielding mechanisms. The paper deals with the estimation of dynamic effects of various devices and mechanisms used in underground works. At this stage, the problems of oscillations of the surface of an elastic half-space from various point sources of waves located at different depths, taking into account the waves reflected from the free surface, are solved. The distribution of stresses and displacements during wave propagation in elastic media is a complex picture. In confined media the picture of wave propagation becomes even more complicated due to reflection of waves from boundaries. The reciprocity theorem is used to estimate the levels of ground surface oscillations created by dynamic effects of various devices and mechanisms during shield tunneling. The dynamic effects of working mechanisms are modeled by: the force directed along the axis of the shield, a pair of forces, two pairs of forces without momentum, a combination of a pair of forces and a longitudinal force, a combination of two pairs without momentum and longitudinal force.