The sedimentary rock that comprises coal measures has quite nonlinear, elastic, stress – strain characteristics. It is also affected by the fluid pressure within it. The fluids act in two quite separate ways. The first way in which fluid acts is in a poroelastic manner while the second is within fractures. These effects are important in rock behaviour, extending from the deformation around a roadway to failure within an outburst. This paper presents the results of detailed laboratory studies into coal and sedimentary rock properties. It relates these to the real situations seen in mining.