The mudstones taken up here belong to the Miocene Mae Mo Group(Sithiprasana 1959). The Group is composed of mudstone beds interbedded with lignite beds. The beds have been designated alphabetically from bottom to top. The mudstones tested here belong to the beds on and under the upper most lignite bed 0. The mudstone under the lignite bed belongs to the bed O and mud— stone on the lignite bed belongs to the bed P. The mudstone 0 contains seams, lenses and fragments of lignite and shows grayish appearance. Mudstone P is rather massive and is whitish colour containing less amount of carbonaceous shale and lignite. Sample blocks were collected from the same horizon within each of the beds.
Blocks of rock were separated from the bed by using a power shovel to avoid fracturing by explosives. Several blocks of fresh rock weighing about 30kg each were selected.
All of these blocks were then coated with paraffine wax immediately to keep the natural water content. These blocks of the mudstone were regarded as the undisturbed mudstone 0 and P respectively.
The coated blocks were transported by a car and were kept in the moisture controlled room at 20°C in the soil laboratory of the Asian Instiute of Technology.
Undisturbed specimens were prepared from the blocks according to the object of the test performed.
For water content detemination ten irregular shaped lumps of rock each weighing about 50g were taken out of every sample block to obtain the average value of natural water content.
For grain specific gravity determination the lumps separated from the undisturbed blocks were pulverized by a crusher to pass the 74 μ sieve. For other physical property determination cubes approximately 5×5×5cm were cut from the random blocks.
(Figure in full paper)
For swelling test the end surfaces were cut at right angles to each axis and were ground by a lapping machine to make them smooth. The axes were made parallel or perpendicular to the bedding plane. For slake durability test about ten roughly spherical lumps each weighing about 50g were prepared and two tests were performed for each mudstone.
For the mechanical properties and permeability tests, the NX core specimens were drilled from the undisturbed blocks by using a hand operated coring machine. The core specimens were prepared both parallel and perpendicular to the bedding.
The shape and size of the specimens for mechanical property tests were followed after the method suggested by the ISRM.
For preparing the specimens at dry state the specimens after obtained the required shape and size were dried firstly at room temperature for about three days, secondly they were dried in the silica gel dessicator for about seven days at room temperature and then they were oven-dried at 105 °C for 24 hours. By this procedure the cracking of specimens was avoided.
(Figure in full paper)