An investigation into the relationships between rock classification systems and engineering rock parameters used in project planning of underground road tunnels

Due to growth in population and scarcenesof avaliable land, the use of underground as well as ground surface is becoming more demanded. Rapid developments in technology led to development of new solutions and methods of construciton in civil engineering works. One of the fields in which theese new improvements have been widely used in the construction of underground facilities and employment of tunneling solutions. A tunnel is a well defined balance of the excavated materials, ecavation techniques and the support system used. Therofore, its design and construction are the most difficult and complex responsibility of engineer, when compared with those of other structures. To provide safe excavation conditions and obtain most appropriate support systems, it is necessary ton consider three seperate factors mentioned above. Tunnel designs require interdisciplinary studies because of the specific interactions of geological units that are very complex in structure. Experts need to talk in the same way technically in order to be able to design an economical and safe tunnel in a short time. Standards and specifications have been established for this purpose, experts from different fields will come together to design the most accurate, safe and economical tunnels in a shorter time. The excavation and support methods of the tunnels in our country are made according to the Technical Spesification of Highways (KTŞ) prepared by General Directorate of Highways. This classification defines rock mass behavior. Supporting system to be applied in tunnel is determined by considering KTŞ classes which are associated with RMR and Q classifications. The work to be done in order to open the tunnel after tunnel construction decision is taken; time consuming, highly detailed, a process that depicts the tunnel line and, depending on it, requires the selection and implementation of the best construction method. The precisely and sensitively attitude enables minimize both uncertainities during excavation and the potential negative consequence. In addition, it will provide the highest level and qualified information to right classification for rock mass. Classification of rocks for engineering purposes makes it easy to determine the most economical and safe solutions and cost anlysis of project. For this reason, many researchers have made different classifications according to different characteristic. One of the major problems encountered in designing rock structures constructed on well jointed rock masses is the difficulty in determining the strength and deformation characteristics of rock masses. Theoretical and empirical difficulties are encountered as to how these properties are to be determined for rock masses. It is at the forefront of these difficulties that it is impossible to take samples from rock masses together with the discontinuities they contain, in order to representational dimensions for laboratory experiments, and to shared control the behavior of rock masses both by rock material and by discontinuities. However, the most commonly used methods for the determination of the strength of rock masses have been included as a result of studies to handle the mentioned difficulties. This thesis study is divided into 6 sections. In the first part, the issues that are important during the project and construction of the tunnels are discussed briefly. Then the purpose of the thesis study and the methods that are followed during the study are explained. In the second part, it is emphasized the steps such as dimensioning of support systems, formation geological-geomechanic-geotechnical models and route studies. In the third part, a literature survey on rock quality and rock support classification systems was investigated and informative information on nationally and internationally accepted classification systems has been given. In the fourth part, the methods of many researchers who have worked to determine the geomechanical magnitude of rocks in the field are scrutinized. In the fifth chapter, the relations between rock quality classifications and in situ rock strengths will be examined in order to provide basis for determination of support systems. In the sixth part, all the results and evaluations are obtained and the relation between the rock support systems of the new model is presented. If the tunnel projecting stages are generalized, a workflow appears where systematic steps are followed. The purpose of this thesis is to reveal the relationships between the geomechanical parameters reflecting the environmental properties and the rock classifications made from the environment characteristics. Within the scope of the thesis study, geological and geotechnical parameters used in project phase of 57 different tunnels in our country were utilized. For this purpose, parameters are separated according to KTŞ classes in order to associate the data which is obtained easily. Then, the values of each class are averaged and compared. On the other hand, the two most relevant parameters, the on-site elasticity modulus and the RMR values, were compared with the minimum and maximum values. Work with the averaged data; the coefficient of determination between internal friction angle and cohesion was found to be about 70%. Apart from that, the ratio is 90% or more. Also, when compared to studies that other researchers have done, the trend line is among others. Studies based on modulus of elasticity at minimum site; in general, the coefficient of determination is 70% or more. Cohesion, RMR, and GSI have low levels of association with the internal friction angle, although there is over 90% compliance in exponential functions. Studies based on modulus of elasticity at minimum site; in the studies in which the relationship of the elasticity module with RMR is investigated, the determination coefficient is 90% or more. However, in relation to the GSI, the rate has fallen to 70%. The ratio of cohesion to RMR and GSI is up to 80%, but the level of interrelationships is very low with internal friction angle. Work based on minimum RMR; the highest determination coefficients (> 90%) were determined in relation to the in situ elasticity modulus with GSI. Relations with RMR have reached a maximum of 60%. The cohesion, in relation to the internal friction angle, RMR and GSI, is generally of the order of magnitude lower than 70%. Work based on maximum RMR; the coefficient of determination of the relation of the elasticity module with RMR and GSI is generally over 70% and sometimes over 90%. Although the ratio of cohesion, internal friction angle, and RMR ratios has rarely reached 70%, it is up to 99% in relation to GSI. The relations established show that; trend lines are generally consistent with the work they are doing in comparison to other researchers. However, the comparative data bear general features of the tunnels projected on both sides of the world and our country. In order to obtain more specific and precise judgments, investigations should be done according to the regions and rocks. Comparisons made in the thesis study are generally made between two different parameters. The effects of multiple parametres should be considered together to determine rock quality classifications and onsite rock strength parameters that are very complex and under the influence of many features.