THE AIM IS TO DEVISE A METHOD FOR CALCULATING THE TIMBERING AND WALLING NEEDED IN HIGHLY FISSURED GROUND.

THE NOVEL ASPECT OF THE RESEARCH PROGRAMME IS THAT IT TAKES ACCOUNT OF BEHAVIOUR AFTER FISSURING.
ATTEMPTS TO ASSESS THE BEHAVIOUR OF FISSURED GROUND UNDER REAL CONDITIONS HAVE BEEN CONFINED TO ELASTIC AND ELASTO-PLASTIC SMALL-SCALE DEFORMATION MODELS. THE RESULTS THUS OBTAINED ARE DIFFICULT TO COMPARE WITH OBSERVATIONS IN THE FIELD.
The target of the research work was to establish a method for calculating the characteristics of the support system required in highly jointed rock masses. This method has been based on the modelling of the interaction between a support whose mechanical properties are generally well known and a rock mass whose global mechanical behaviour is not easy to quantify, being the result of the combination of the reactions of the matrix and the joints. The study was intentionally restricted to the case where, inside of the rock mass, the spacing between the joints is small enough, with respect to the dimensions of the openings, to reasonably enable the substitution of an equivalent continuum to the set of blocks limited by joints that constitute the actual rock mass. The design of the support systems requires a good knowledge of the behaviour of the jointed rock mass. A new theory is proposed to deduce this behaviour from the degree of joints existing in the mass. A series of experiments has been carried out on concrete semicircular arches of 1 m of internal diameter and 2 m of external diameter with various hand made degrees of jointing in order to verify the theory. The good agreement between experience and theory proves the validity of the approach of the equivalent continuum for highly jointed rock masses and enables the design of roof support based on the modelling of the interaction of the support and the equivalent continuum.
THE PROJECT IS IN THREE PARTS :
- AN EXPERIMENTAL PART IN THE LABORATORY TO OBTAIN SPECIFIC DATA ON THE BEHAVIOUR OF A STRUCTURE IMMEDIATELY AFTER FISSURING.
- A THEORETICAL AND NUMERICAL PART (MODEL) TO DEVISE SOFTWARE CAPABLE OF PREDICTING THE BEHAVIOUR OF FISSURED STRUCTURES.
- AN ON SITE EXPERIMENTAL PART TO VERIFY THAT THE PROCESS IS ADEQUATE TO MEET THE NEEDS ARISING FROM A SITUATION (FIELD TRIAL).

THE USE OF SCALE POST FISSURING DEFORMATION MODELS WILL MAKE IT POSSIBLE TO EXPERIMENT MORE CLOSELY TO REAL CONDITIONS AND TO TAKE ACCOUNT NOT ONLY OF THE INITIAL NATURAL FISSURING OF THE MASSIF BUT ALSO OF FISSURING DUE TO DRIVING DURING EXCAVATION WORK.

THE MINING INDUSTRY IS ASSOCIATED WITH THE PROJECT AND WILL ULTIMATELY USE THE PROCESS FOR CALCULATING THE TIMBERING AND WALLING NEEDED.