Abstract

An experimental study was carried out on grout samples prepared from both Stratabinder and BU100 cementitious products. Samples were prepared with various water to grout ratios and tested for uniaxial compressive and shear strength. Triaxial tests were performed on cylindrical samples to determine values for internal friction angle, cohesion and tensile strength. It was found that the water to cement ratio affects the uniaxial compressive and shear strength of grout. The triaxial test indicated that both internal friction angle and cohesion of Stratabinder do not differ significantly from BU100.

1. Introduction

Prior to the late 1940's, a large proportion of roof supports in underground mines in Australia consisted solely of timber deployed along roadways. The fragile nature of the timber was the cause of a considerable roof failures and rib collapses prior to the introduction of roof bolting. The early roof bolts consisted predominantly of a mechanical anchor positioned at the base of the drill hole. Subsequently, the fully encapsulated rock bolts were developed to bind the bolt and surrounding rock after installation by means of resin or grout. The capability of load transfer of an encapsulated rock bolt is influenced by the resin or grout mechanical properties.

Aziz et al. [1–3] carried out a detailed research study with the aim of establishing a general practice standard for determination of mechanical properties of resin. The study included; determination of the Uniaxial Compressive Strength (UCS), the Elastic modulus (E) value in compression, shear strength and rheological properties. These mechanical properties were examined at the University of Wollongong laboratory in relation to resin sample shape, size, height to width or diameter ratio, resin type, resin age and cure time. The following conclusions were reported:

  • The UCS values determined from various shaped samples differed with respect to the sample shape and size and height to diameter ratio,

  • Typically, the UCS values were highest for 40 mm cubes and 40 mm diameter cylindrical sample with height to diameter ratio of two,

  • The ratio between cube strength and cylinder strength varied from El to 1.3,

  • The E value increased as the resin sample curing time increased from 7 to 21 days,

  • The cube samples exhibited higher E values in comparison with cylindrical specimens at various curing time,

  • Similar to UCS values, the average shear strength of grout samples increased with increasing curing time,

  • Cube samples were suggested as a universal shape for testing resin products as they can be easily prepared and tested.

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