Screw-in Soil Nail for Slope Reinforcement Against Slip Failure: A Lab-Based Model Study

Abstract

Slope failures occur when the shear resistance along the slip plane is exceeded. This can be caused by excessive load imposed at the slope crest or compromised stability of the slope, e.g. disturbed dimensions of the slope. In order to prevent slope failure, stabilisation or reinforcement measures need to be taken. A common solution is to intercept the slope failure plane with reinforcement elements, such as soil nails and ground anchors. In soil nailing, reinforcement bars are installed on the slope to effectively resist the additional shear forces from the imposed loads, hence reducing the probability of failure in the long run. This paper describes the innovation of soil nail with screw-in installation mechanism instead of the conventional push-in approach. The screw-in installation ensures better soil-nail grip and less disturbance during the slope stabilisation procedure, especially in terms of noise and spoils. In addition, the novel nail has a hollow stem which improves shear resistance with greater soil-nail surface contact on the inner wall. The opening at the nail head also enables displaced air to escape as the nail is screwed into the slope and soil pushed into the inner hollow cavity. The prototype nails were tested in a slope model with different configurations, and were found to reduce the Angular Distortion Ratio by 37 % and the Volumetric Deformation Index as much as 33 % respectively. The novel screw-in soil nail could be potentially used to stabilize natural and man-made slopes, though full-scale simulations are recommended to formulate the installation procedure and to validate the effectiveness.

On the Nailed Soil Slopes Research Development

“…While reference [42] study the laboratorium model of screw-in soil nail for slope reinforcement against slip failure and they summarized that the novel screw-in soil nail could be potentially used to stabilize natural and man-made slopes, though full-scale simulations are recommended to formulate the installation procedure and to validate the effectiveness.…”

Influence of Grassroots on the Stability of Slopes: Experimental Modelling and Numerical Analysis

“…The grass that was popularly used to overcome landslides was vetiver grass (Vetiveria zizanioides) because this plant was an annual plant that grows upright with a height of 1.5 -2.5 m with a unique root system; its fibrous roots were able to penetrate very deep and reach a long distance, more than 3 meters and the record for the longest root was 5.2 meters, which was found in Doi Tung, Thailand [16]. Vetiver root penetration can increase the safety factor in terraced slopes [17]. Shear strength tests in the laboratory on soil samples with vetiver grass roots decreased with increasing water content-however, higher root length results in higher shear strength [18].…”