A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1985

This research was conducted to investigate the characteristics of compressibility and shear strength on greywacke rockfill for CHIEW LARN DAM, SURATTHANT province, southern Thailand. A review of known investigation of engineering behaviour on granular materials in presented herein, along with the experimental results of author's studies on this subject. The experimental work described herein includes mainly two parts. The first part consists of 22 triaxial tests, organized in series of drained (17 tests) and undrained (5 tests) triaxial compression tests. Rockfill samples were prepared at a dry density of 2.0 and tested at various confining pressure of 5-140 t/m2. All triaxial specimens were 4 inches in diameter and 8 inches high with the maximum particle sized varying from 3/4 to 3/8 inches. Angles of internal friction measured from drained tests were 36.7 to 48.7 degrees depending on which gradation and confining pressure was adopted, while those measured from undrained tests were 38.7 to 45.4 degrees. The second part consists of 8 rarge-scaled oedometer tests, divided into two groups on the basis of different specimen sized. The tests of large size specimens (724 mm dia. x 1000 mm high) were conducted in dry condition and those of small size specimen (9-in dia. x 4-in high) were performed on both dry and saturated samples. All specimens of oedometer tests were prepared at a dry density of 2.0 as well as the triaxial specimen and tested under the static axial load up to 220 t/m2. Vertical strain of 3.3% to 5.4 % were measured on dry samples of different gradations at this stress level corresponding to the particle breakage of 1.5 to 5.1 %. While the vertical strain measured on saturated sample were 7.6 to the vertical strain measured on saturated sample were 7.6 to 8.2 % Through all these triaxial and large-scaled oedometer tests, the effect of the gradation, the particle size, and the stress level on the compressibility and shear strength of greywacke were investigated. The comparison of drained and undrained condition of triaxial tests, dry and saturated samples for oedometer tests were also studied and discussed.