Numerical analysis of freezing and thawing influence on soil nail wall

Jinyuan Liu

In the proceedings of: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: INFRASTRUCTURE - 1 Highways & Bridges

ABSTRACT: This paper presents a numerical investigation on the effect of freezing and thawing on a soil nail wall and to predict frost penetration and its influence on nail load and facing pressure in frost susceptible soils. Soil nailing is a relatively new technique of reinforcing existing slopes or supporting new excavations. Its performance has been proven through decades of successful applications throughout the world. However, its applications in cold regions are very limited due to the concern on its durability and lack of knowledge in the response of wall to freezing and thawing cycles. In addition, soil may dramatically change its properties after experiencing freezing and thawing cycles. This paper addresses this issue by numerically simulating the effect of frost action on a soil nail wall using a finite element program, ABAQUS. In this study, heaving and frost-induced stresses in nails under various thermal regimes will be modeled and compared with a well-documented study in Maine, US. This study will provide valuable insight into the behavior of soil nailed structures in cold regions.

RÉSUMÉ: Cet article présente une étude numérique sur l'effet du gel et du dégel sur le sol des murs des ongles et de prévoir la pénétration du gel et de son influence sur les charges à ongles dans les sols sensibles au gel. Le clouage du sol est une technique relativement nouvelle de renforcer les pentes existantes ou de soutenir des fouilles. Sa performance a été prouvée par des décennies d'applications réussies dans le monde entier. Cependant, ses applications dans les régions froides sont très limitées en raison de l'inquiétude sur sa durabilité et le manque de connaissances dans la réponse des murs aux cycles de gel et de dégel dans les sols. Cependant, des cycles du gel and du dégel peut changer les propriétés radicalement. Ce document vise à résoudre ce problème par simuler l'effet numérique de l'action du gel sur les parois des ongles du sol à l'aide d'un programme d'éléments finis 2-D, ABAQUS. Dans cette étude, le soulèvement et les contraintes induites par le gel dans les ongles sous divers régimes thermiques seront modélisés et comparés avec une étude bien documentée de Maine, États-Unis. Sur la base de cette étude, une méthode simplifiée est proposé d'incorporer l'action du gel dans la conception de la paroi de l'ongle du sol. Cette étude fournira des informations précieuses sur le comportement du sol cloué structures dans les régions froides. 1 INTRODUCTION A soil nail is a structural element which provides load-transfer to the ground in soil retention applications. The "nail" may simply consist of a steel tendon. But most commonly the tendon is encapsulated in a cement grout to provide enhanced load transfer and corrosion protection. The main reinforcing mechanism of soil nailing is to reinforce and strengthen the existing ground by installing the steel bars or nails close to each other. Soil nailing has proven to be very cost-effective for shoring temporary excavation or stabilizing slopes. The long-term performance of soil nail walls has been proven after four decades of various successful applications in the world. Soil nailing has been used for both temporary and permanent applications. However, in cold regions like Northern Ontario, the influence of freezing and thawing cycles on a soil nailed structure and its performance and durability is to be answered. Soil nailing applications in cold regions have been limited so far due to the sparse research on its performance in frost prone areas. Soil nail walls (SNWs) constructed in cold regions are susceptible to experience increased nail loads due to frost formation. Damage to soil nail facing has been reported (Byrne et al. 1996) and settlements of the soil behind the wall may also occur when the frozen soil thaws. The behavior of soils in cold regions is strongly influenced by temperature; therefore, the analysis of ground thermal regimes is important in many problems of scientific interest. In addition, to allow for a proper design, the thermal interaction of engineering structures with frozen ground must be understood properly. Frost heave-thaw effects conceivably could result in many damages, including nail rupture, facing cracks, or nail head pullout, although no specific reports of this type of failures were available. This implies that the nail spacing adopted in current designs may be adequate to protect against frost failures in the soil surrounding the nails. However, this inference cannot be confirmed

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