This paper firstly describes the results of physical simulation tests about the strengh property and the deformability of the rockmasses with four types of ordered joint sets in them and then puts forward a new constitutive damage-fracture model as well as its evolution equation. The paper, in addition, describes the corresponding FEM programme for the analyses, the comparison calculation shows that the testing results and calculating ones are well coincident.
Les resultats de simulation physique pour les proprietees de resistance et de deformation de massif rocheux avec quatre types d'ordre joints sets sont presentes dans cet article. Un nouveau model constitutif de dommage-fracture et leur equation evolue pour les massifs rocheux fissures est propose. Le programme correspondant par la methode d'elements finis pour I'analyse est intriduit, la comparaison de calcul montre que le resultat d'essais et celui de calcul est bien coincident.
lm vosliegenden Aufsatz wesdwen die Ergebnise ueber physikalish Simulier-Unter-suchung der Festigkeit und Deformations der Felsmassife mit den vier Typen der geordneter Klutschar beschreiben. Ein neuer, kunstitutiunell Schad-Brucksmodel und Evolutionsgleichung wird ausgestellt. Die Asbeit zeigt auβerdem eine entsprechend Programrn der Finite-Element-Methode fur ein Model; die Gegenueberstellung mit die Ergebnisse der Berechnungsverhalten und der experimentellen Modelluntersuchungen entsprechend ist.
Most of rockmasses encountered in engineering are jointed, nothing more than that the joint sets have developed to different extent. These joint sets were mostly formed in very long previous geological structural movements, so there exists a certain regulation about the orientation and the scale of the sets. The emphasis will be put on researching ordered joints in this paper. The strength property and the deformability of jointed rockmasses are affected by many factors, so physical simulation tests should be carried out first to get a certain law and then, based on this to find an effective analyzing method. At present, the method combining damage mechanics and fracture mechanics to analyze strength property and deformability of jointed rockmass is very promising, at which this paper aims.
The simulating material should be similar with prototype rockmass in basic mechanical properties, i.e. it should follow the similarity law; besides, the material should have a constitutive curve similar with the prototype's. It should be especially noted that the simulating material should have the dilatancy property corresponding to the prototype. Many researchers either pay less attention to this or have not mixed this kind of material. Having tried and tested for ages, we have successfully mixed a simulating material consisting of yellow sand, barite powder and polyvinyl with white latex in a fixed mixture proportion. The whole jointed model is composed of many small blocks, some or them are cemented together and some are free.
A damage-fracture model (Li & Zhu, 1992) will be introduced to analyze the previously stated testing results.
Jointed rockmasses will present obvious dilatancy phenomenon before failure; the kickpoint value in volumetric curve will increase with the increment of confining pressures, generally, σo is about 0.6 – 0.9 times of the peak strength value. There are two failure models, for a lower confining pressure, the rockmass failure will take place longitudinal split form; which for a higher confining pressure tensile cracks will result longitudinally (along σ1 direction) at crack tips and then shearing failure will take place through the rock bridge along the crack orientation.