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The work presented in this thesis has been concerned with investigation of the geomechanical behaviour of laminated weak roof strata along longwall roadways in underground coal mines and the mechanisms for effective reinforcement. Field investigations have been particularly associated with underground conditions at Angus Place Colliery, New South Wales, Australia. The principal objectives of this investigation are to understand the deformation behaviour of the laminated weak roof strata and the roof reinforcement problems which have plagued longwall roadway support and underground mining in West Coalfield of New South Wales. Based on the comprehensive engineering understanding of the geomechanical behaviour of laminated weak roof strata, an appropriate reinforcement strategy is developed. The thesis consists of four major parts associated with different approaches adopted in conducting the investigation, including: 1. Laboratory investigation: Conventional deformation and strength parameters of major roof rocks, such as, coal, mudstone and sandstone, including modulus of elasticity, uniaxial compressive strength, (UCS), uniaxial tensile strength, cohesion and angle of internal friction, along with shear strength, triaxial compressive strength with different confinements, have been conducted, in order to determine the mechanical properties of roof rock masses. On the other hand, a series of tests has been conducted to investigate the water sensitivity of mechanical properties of roof rocks, in order to evaluate the effect of water on mechanical properties of roof rocks and to determine the deterioration mechanism of roof rock. According to the results, the intact roof rocks can be classified from medium strong to weak rock mass subjected to the 0% water content. When the water content and discontinuity have been taken into consideration, the roof and floor strata in maingate 22, Angus Place Colliery can be classified as a weak strata. In general, the mechanical properties of surrounding rock masses, the integrity of roof and floor structures are significantly influenced by discontinuity and water. 2. Mine site investigation: The major purposes of this work are to determine the detailed roof deformation behaviour and roof layer separation in the roof strata and the performance of rock bolting reinforcement system used in longwall roadway by using the wire and sonic extensometers and instrumented bolts. According to this work, the roof deformation is differentiated into three different stages associated with different mining activities, that is: a) stage of development, b) stage of time dependent deformation (after development and before extraction) and c) stage of extraction. On the other hand, the deformation behaviour at different horizons associated with different roof geological settings is also determined. Correspondingly, the rock bolting performance is monitored including the maximum axial load, the distribution of load along the length of bolt, the bending moment of bolts as well as the load variation with different stages during the mining. 3. Parametric study: The parametric study is conducted by two and three dimensional computer modelling using Map3D and Phase2. Three dimensional modelling determines the stress redistribution and deformation around opening after roadway development and during the longwall extraction, which provides basic stress parameters as reference for the two dimensional modelling. In two dimensional modelling, the comprehensive parametric study on rock bolting reinforcement system and grouting reinforcement has been conducted. It is noted that the roof stability can be improved through three different ways, which are: a) optimising combination of rock bolting parameters, such as, bolt length, pretension, inclination, stiffness, distribution, etc, b)using combined reinforcement methods, such as, rock bolting and grouting reinforcements, c) altering geometry of opening, particularly for the rectangular shape of opening. 4. Theoretical analyses: The principles of material and structural mechanics have been used and based on these mechanical theories, the roof deformation mechanisms have been developed associated with different stages of mining activities. Based on the outcomes of the study, the reinforcement strategy has been developed using three approaches, including, a) the features of underground geological and geomechanical conditions and deformation behaviour of opening, b) the reinforcement methods and parameters, and c) Principles of New Austrian Tunnelling Method (NATM). Also, the procedure for development of reinforcement strategy has been proposed which can be used as a guide for evaluating the deformation behaviour and developing the reinforcement strategy under different adverse ground conditions.