An Experimental Study on Reinforcing Rock Columns Using Heated Polymeric Ties

Abstract

Load-bearing rock column and pillar reinforcing without a permanent visual change is an important advantage for applications in both historical and modern sites. One of the most widely seen column reinforcement methods is using steel collars which can cause a visual change on rock surfaces because of its corrosion problem and hardness. Steel collars are mostly used to reinforce rock columns with regular cross-sectional shapes, but not suitable for being used to reinforce rock columns with irregular crosssectional shapes because of their high stiffness which prevents them from being shaped by the column body. Rock column reinforcement method can be divided into two groups: active and passive reinforcement methods (Moghaddam et al. 2010; Bieniewski et al. 1969; Komurlu et al. 2013; Spencer and Gardner 2003). In passive reinforcement method, confinement pressure is supplied as a reaction to the deformation of the rock surface in contact with the reinforcing devices. On the other hand, active reinforcement pressure can increase the load-bearing capacity without a deformation of columns/pillars (Holmes et al. 2014; Windsor 1987; Kovari et al. 1983). Polymers can be divided into two groups: thermoplastics and thermosets, according to their reaction to being heated (Wigley 1971; McCrum et al. 1997; Komurlu and Kesimal 2014). Thermosets cannot be softened and extended easily by heating. Generally, their polymerization process transforms the liquid components into a plastic or rubber by cross-linking. Thermosets are not able to be remolded by heating after their initial formation (Pascault et al. 2002; Tadlaoui et al. 1993; Ebewele 2000). Therefore, thermosets are generally polymerized in molds. In case of heating with high temperatures, cross-links of thermosets are broken without melting. On the other hand, thermoplastics, also called as thermosoftening plastics, can be deformed easily and shaped by heating. Thermoplastics harden and strengthen by cooling, which can preserve the original length or shape after cooling from a temperature level depending on the type of product (Akay and Barkley 1985; Komurlu and Kesimal 2012). Therefore, the use of thermoplastics should be considered for the aim of active reinforcement pressure applied on rock columns encircled with heated ties. Polymer materials are used for different reasons varying within a large range. An important percentage of polymer usage is because of their good chemical resistivity as in applications of food packing, transport of drinking water, hot water or gases (RTMSTI 2010; Ohtomo and Ohnuma 2014; Castagnet and Grandidier 2006; Siracusa et al. 2011). Polymer materials used considering their strength values are generally engineering polymers which have better mechanical properties in comparison to most of the other polymeric materials (Troughton 2008; Komurlu 2012; Komurlu and Kesimal 2011). Also, the chemical resistance of the engineering polymers is an important reason, making them convenient to be used as an alternative to conventional engineering materials. & Eren Komurlu erenkomurlu@gmail.com; ekomurlu@ktu.edu.tr