Desenvolvimento de modelos de previsão do comportamento cisalhante em descontinuidades sem preenchimento de maciços rochosos utilizando técnicas fuzzy e neuro-fuzzy

Abstract

One of the main problems involving the analysis and the design of geotechnical structures in rock is the correct prediction of the behavior of the rock masses. This is because rock masses normally consist of an interlocked array of discrete rock blocks with varying degrees of weathering and discontinuities that may be cleaned or filled with some type of material.Therefore, the development of accurate and reliable models for predicting resistance of rocks and rocky masses is one of the most common interests among engineering and geology professionals. Several studies have shown that the mechanical behavior of rock masses is directly related to the shear behavior of their discontinuities. In general, it is observed that the shear behavior of unfilled rock discontinuities is influenced by their contour conditions (CNL and CNS), the roughness characteristics of the discontinuities, and the properties of the intact rock. Studies have been conducted, and a number of analytical models that can be used to predict the shear behavior of unfilled rock discontinuities have been developed. However, all of them have a purely deterministic character, since their input variables are defined without taking into account the uncertainties inherent in the formation process of the rock mass and the discontinuity itself. Therefore, the objective of this work is to present models of prediction of shear strength and dilatancy in unfilled rocky discontinuities that take into account the uncertainties in the values ​​of the variables that govern their shear behavior using fuzzy and neurofuzzy controllers. For the development of the models, results from 44 directionalised shear tests were used in different types of discontinuities and contour conditions. The input variables of the models are the normal stiffness and initial normal stress acting at the discontinuity, its roughness expressed by the JRC, the simple compression strength and the basic friction angle of the intact rock, in addition to the shear detachment imposed on the discontinuities in filling. The results revealed that, in general, the proposed fuzzy and fuzzy models presented satisfactory predictions of the shear behavior of discontinuities without filling.