The swelling properties and mechanical properties of limestone was investigated under high temperature from 200 °C to 700 °C and bidirectional restraint with the device used to heating rock designed by ourselves and servo-control testing machine RMT-150C.The experimental results show that the two directions′ swelling stress of limestone increased with temperature rising before 600 °C

and decreased after 600 °C or 650 °C.The swelling stress perpendicular to bedding plane was bigger than that parallel to bedding plane.The curves of swelling stress and temperature ascended smoothly with time under constant temperature before 600 °C

but the slopes were much less than those during temperature rising.The swelling stress tended to be a steady value at last under constant temperature.When constant temperature ended

the swelling stress was smaller than those before constant temperature at 700 °C.It showed that the limestone had swelled to the limit value after a certain temperature.The peak-stress of limestone decreased gradually with temperature increasing and the peak-stress at 700 °C decreased 58.92% comparing to room temperature.It showed high temperature can weaken the strength of limestone evidently.The peak-strain increased before 500 °C firstly

and then reduced after 500 °C.The swelling stress and peak-strain may reduce after a certain temperature because the rock sample was restricted and some fissures closed and the number of cracks reduced under over-high temperature

but the detailed reason needs more researches to testify.