Numerical Investigation of a Foundation Pit Supported by a Composite Soil Nailing Structure

Abstract

In special geology conditions such as silt-soil, foundation pits are prone to instability and severe deformation. In this paper, a composite soil nailing structure was studied and its effect on a silt-soil symmetrical foundation pit investigated. The factors affecting the stability of the pit as well as its deformation characteristics were also explored. The results show that excavation depth of the foundation pit has a significant impact on its stability. The soil outside the foundation pit is in the form of a parabola, and the uplift of the soil mainly occurs at the bottom. The horizontal displacement of soil on the side wall of the foundation pit presents a “bulk belly” form. In addition, the axial force of soil nails is larger in the middle part, and smaller at both ends in the shape of a spindle. Moreover, the horizontal displacement is positively correlated with the inclination and spacing of the soil nails, but negatively correlated with the diameter and depth of the mixing pile inlay. Furthermore, the inclination and spacing of the soil nails, the diameter, and embedded depth of the mixing pile have their own critical values for stability of the foundation pit. Specifically, in this paper, with respect to soil nails, inclination should be below 30° and prestress value should not exceed 20 kN. With respect to the mixing pile, the diameter should be less than 1.5 m; when the embedded depth of the mixing pile exceeds the critical depth, the limiting effect of the mixing pile on horizontal displacement is not significant. This research provides important takeaways for the design of a composite soil nailing structure for symmetrical foundation pits.

Breaking and Instability Movement Characteristics of High-Position Double-Layer Hard Thick Strata due to Longwall Mining

“…According to the actual geological condition of panel 1061, a UDEC numerical model with the size of 700 m (length) × 450 m (height) is established to simplify several strata in order to simulate the mining state of 550 m, and then the mining stress evolution and plastic zone expansion affected by the DLHTS breaking are studied. Herein, the model boundary, loading method, and conditions are all applied, referring to the actual conditions and previous references [27][28][29][30]. Limited by the length of the paper, this section will directly show and describe the nephogram of mining stress and plastic zone before and after the DLHTS breaking.…”

Multi-factors influence of anchorage force on surrounding rock under coupling effect of creep rock mass and bolt/cable

“…As an important and effective support material, bolts and cables are widely used in many engineering projects, such as coalmines, tunnels, hydropower stations and slopes (Xu et al 2018;Zhang et al 2019;. With the gradual development of coalmines and tunnels to deeper area, the mechanical environment is increasing complex, and the geological and mining environment of surrounding rocks tend to be worse Jiang et al 2019;Han et al 2020;. Moreover, the surrounding rock of roadway with high in situ stress often undergoes obvious rheology, which seriously affects the roadway stability (Zhao et al 2017;Wang et al 2019).…”

An Experimental Study of a Nailed Soil Slope: Effects of Surcharge Loading and Nails Characteristics

“…Benayoun et al [24] proposed the optimization of soil nailing parameters for soil-nailed structure design, using the genetic algorithm method. A composite silt-soil nailed symmetrical foundation pit was numerically investigated by Han et al [25] for stability and deformation characteristics. They found the critical values of inclination and spacing of the soil nails, and the diameter and embedded depth of the mixing pile for stability of the foundation pit.…”