| Abstract | Volcanic rocks of Khlong Tha Dam site consist of agglomerate, tuff, andesite and rhyolite. These rocks were tested to determine engineering properties and their suitability for construction material. Two types of agglomerates are andesitic and rhyolitic. The andesitic agglomerate was green to grayish green, clasts or framework were anesite, some rhyolite fragments. Matrix was andesite. Rhyolitic agglomerate were less found, phenocrysts and matrix were also divided in two types, andesitic tuff and rhyolitic tuff. Andesitic tuff was green, brown, and purple in color. Rhyolitic tuff was seldom found and its color was white to pale brown. Andesite was green, brown and sark gray. It composed of plagioclase and hornblenfde. Rhyolite was white, light gray, and light purplish gray. It is composed of feldspar and quartz. The strength properties of agglomerate, tuff andesite and rhyolite are respectively as follow; point load strength Indices are 9.25, 10.49, 11.38 and 9.39 MPa; tensile strength are 12.88, 14.81, 15.17 and 12.18 MPa; unconfined compressive strength are 101.7, 109.8, 134 and 76.28 MPa; The shear strength parameters, c and , which were obtained from direct shear test, the cohesion are 16.5, 16.19, 21.87 and 17.7 MPa; the internal friction angles are 74.2, 73.7,m 74.1 and 70.3 degree; cohesion obtained rom triaxial compression test are 10.39, 11.05, 13.41 and 6.48 MPa and internal friction angle are 65.39, 65.33, 65.73 and 70.22 degree; modulus of elasticity obtained from unconfined confined compression test, Young modulus are 58.86, 61.11, 44.31 and 50.17 GPa, and poisson's ratios are 0.21, 0.26, 0.28 and 0.18. Rock Classification based on Deere and Miller (1967) for agglomerates are medium strength, for tuff was medium to high strength, for andesite is high strength, and for rhyolite is medium strength. These rocks were also tested on aggregate properties, the soundness good and can be used. Except for concrete aggregate, alkali reaction test, it was found that tuff, andesite and unaltered rhyolite were suitable for using as construction materials. For Agglomerate and hydrothermal altered rhyolite, it was not suitable for using as concrete aggregate due to causing excessive expansion from alkali in cement and rock material. |