Analytical and experimental study of Shear strength of tension cracks in deep excavations under gravitational grouting

mehdi sony¹ hooman heidarian² alireza moadeli³

1) Civil Engineer-Geotechnical
2) Civil Engineer-Geotechnical
3) Ph.D.-Geotechnical

IOI Code : XYDC-AFFHE
Publication : International Conference on Researches in Science & Engineering(icrsie.com)
Abstract :
    Excavation in construction projects, alter the stress and strain fields in the walls of the excavation. In cohesive soils, horizontal stress reduction due to the excavation, and lack of sufficient lateral inhibition induced tensile cracks along the walls of the excavation. Infiltration of surface water into the cracks, resulting in hydrostatic pressure in the crack walls. This theme, combined with the reduced length critical slip surface, Leading to reducing the safety factor of the pit walls stability. Improve shear strength along the ground cracks by gravitational grouting cement slurry, one of the traditional methods but lack scientific support is in construction sites. In this study, by modeling shear stresses in the excavations under the conditions of shear stresses in uniaxial strength test, the test for determining the shear strength at the contact surface soil-grout is used. For this purpose, the cylindrical form of cohesive soils samples with different plastic properties of different densities and different lengths have been rebuilt with cracks 45 degrees. These cracks with grouts, with different water-cement ratio, Just Have been filled gravity, and after setting cement, uniaxial resistance is measured. Given the adhesion of soil samples intact (no cracks), With reverse calculations, soil-grout adhesion surface is calculated. Finally, whit a simple modeling in software Slide, The effect of gravity grout injection has been shown to increase the safety factor of a sample excavation.

Keywords : interface soil cement grout tension crack soil improvement excavation safety factor