Classification of rock texture properties and rock engineering applications

Kayaç dokusal özelliklerinin sınıflandırılması ve kaya mühendisliği uygulamaları

Abstract

During the design phases of an underground opening, the characterization of rock mass that is consisted of rock material and discontinuities is important for understanding the stability of underground construction against the loads. Rock mass characterization is determined by combining the strength of rock material, which is assumed to be as homogenous and isotropic, and the properties of discontinuity. Uniaxial compressive strength $(sigma_c)$, point load strength $(I_s)$, and Schmidt hammer hardness (R) can be used for understanding the strength of the rock material. Additionally, the cuttability properties of rocks must be defined in order to understand the machine performance of the cutting machine, the cost of the excavation process, and the cuttability behavior of the rock zones for rock engineering projects. This reality increases the importance of researching the relation between physical, mechanical, and cuttability properties of rocks. On the other hand, rock materials are classified on their strength properties, and the design procedures of the underground openings show similarities for same classes of rock materials.The textural properties of rocks are evaluated by the composition of the grains that form the rock. To evaluate the texture, geometrical properties of the grains which are named as area, perimeter, length, breadth, and orientation must be determined. These properties can be determined by image analysis of the pictures taken by thin sections of the rock material. After determination of these properties, quantification of the rock texture can be possible by using texture coefficient (TC) proposed by Howarth ve Rowlands (1987). They show that there is a relation between TC and rock material strength. In this study, TC is used for classifying rock materials based on textural properties, and the relations among TC and mechanical, physical and cuttability properties of rocks are investigated. To classify the rock material strength based on rock texture properties, the relations among physical, mechanical, cuttability, and textural properties of rocks are investigated. 23 different rock mechanical properties of 5 different study areas are studied for this purpose. Thin sections are gathered from these study areas. After all of these researches, approximately 1000 images taken from 90 different thin sections are analyzed by image processing technique based on using image analysis software. Hence, it is possible to correlate the TC values of rock materials with 23 different mechanical, physical, and cuttability properties of rocks and 43 different relations are investigated.In order to understand the relations between TC and other mechanical properties of rocks, modelling studies are carried out. 43 regression models are constructed for this purpose between TC and mechanical properties of rock material, and 17 of them are selected based on their success and importance and fuzzified. All of these studies are important in order to understand the relation between textural and strength properties of rock materials. The study of appointing TC as an input parameter for rock engineering projects is carried out using on the relation between textural and strength properties suggested here. Firstly, estimation of TC is determined based on the rock material litology, and the expected values of TC are estimated for 14 different litology. After quantifying the rock texture by using TC and classification of TC based on strength behavior, it is possible to use TC for rock engineering discipline. Rock material texture is classified into 5 groups that show the strength properties, and the expected uniaxial compressive and point load strength are determined. Classification studies are also made by fuzzy domain and strength behavior of rock material is estimated by fuzzy the classification model which uses TC as input and uniaxial compressive and point load strength as outputs.After achieving the classification of TC for understanding the strength behavior of rock material, TC is applied for the different rock engineering disciplines. As a result of these, TC is applied for rock mass classification systems such as rock mass rating (RMR). Regionalization of TC and investigation the distribution of mechanical properties based on geostatistical methods, aggregate material degradation estimation and determination of expected TC value of aggregate materials, and lastly estimation of mechanical and cuttability properties of rock material by fuzzy models with expected errors and limitations.

Özet

Yeraltı yapılarının tasarımı aşamasında, inşaatın yapılacağı kaya kütle ortamlarının karakterizasyonu, yapının servis süreci boyunca üzerine gelecek olan yüklere karşı emniyetli olarak hizmet vermesi açısından önemlidir. Kaya kütleleri, kayaç malzemeleri ve süreksizliklerden oluşan sistemlerdir. Kaya kütle karakterizasyonları, kayaç malzemesinin dayanımının ve süreksizlik özelliklerinin değerlendirilmesi ile gerçekleştirilir. Kayaç malzemeleri, homojen ve izotrop olarak kabul edilen ve dayanımları üzerinde malzemeyi oluşturan mineral, minerallerin bulunduğu doku ve tanelerin birbirlerine bağlanmasını sağlayan çimento malzemesinin kompozisyonunun etkin olduğu doğal yapı malzemeleridir. Kayaç malzemelerinin dinamik ve statik yükler altındaki davranış modellerini kestirmek ve yeraltında inşaa edilecek olan yapının amacına en uygun tasarımı gerçekleştirebilmek için, kayaç malzemelerinin mekanik ve fiziksel özelliklerinin tayin edilmesi gerekmektedir. Bunun yanında, dayanım özelliklerine göre gerçekleştirilecek sınıflamalar ile kayaç malzemesinin ve kaya kütlelerinin sınıfları tayin edilebilir. Kayaç malzemelerin dokusal özellikleri ile mekanik ve fiziksel özellikleri arasındaki ilişkilerin varlığı bilinmektedir. Bu çalışmada, kayaç dokularının sayısallaştırılması için Howarth ve Rowlands (1987) tarafından geliştirilen doku katsayısından (TC) faydalanılmıştır. Mekanik, fiziksel ve kesilebilirlik özellikleri belirlenen kayaç malzemelerinin TC değerleri tayin edilmiş ve malzemelerin dokusal özellikleri ile arasındaki ilişkiler istatistiksel ve bulanık yöntemler ile modellenmiştir. Elde edilen sonuçlardan hareket ederek, kayaç malzemelerinin dokusal özellikleri TC’den hareket ederek sınıflandırılmış ve her bir sınıfın dayanım özellikleri tayin edilmiştir. Bu aşamadan sonra ise, TC ile dayanım sınıfı tespit edilmiş kayaç malzemesinin kullanılacağı kaya mühendisliği projelerinde ihtiyaç duyulan tasarım problemlerinin çözümüne yönelik yaklaşımlar geliştirilmiştir.