## 1 Introduction  
The invention of high level explosives in the nineteenth century has made it possible to excavate large scale underground spaces. With the help of explosives used in detonation devices, almost any type of rock can be shattered to create any size of cavity and these type of explosive excavation methods are widely used in tunneling and underground space activities due to their easier and relatively simpler way of usage. However, these blasting methods carry their own limitations, as they are either restricted or not permissible at all in urban areas due to the production of vibration, noise and dust which are, for obvious reasons, unbearable for urban population. Alternatively, tunnel boring machine (TBM) can be used but it can only be used for the construction of large-sized circular openings. TBM excavation is also not possible for all types of urban excavations such as the underground space creation for the provision of public facilities such as roadways, railways, sewage facilities and transmission of electrical lines. Tunnel excavation is a vital part of the construction and development activities in urban areas especially big metropolitans, and the environmental impacts of tunneling such as vibration, noise, and dust production are necessary to be considered in the management of such projects. The considerations stated above require the use of a tunnel excavation method in which the least noise, vibration, and dust are produced. One of such methods involves the use of a non-vibrationalrock splitting method in which a split-wedge system is inserted into the boreholes already drilled in the rock and the operation of split-wedge system causes subsequent splitting of rock segments which are collected and transported out of the site easily [1]. There exists little literature on the analysis and performance of this method in different construction projects. The introductory details of this non-vibrational rock splitting method were overviewed and the drilling and free face forming method for controlled blasting excavation (Kaminiko Tunnel, Japan) was investigated [2]. The applicability of this method was analyzed for the construction of twin-tube tunnels (Follo line project, Norway) using the surface fracturing analysis through FEM (Finite Element Method) simulations [3]. The production of noise level in the whole excavation process (Blasting environmental impact assessment project, South Korea) was found to be less than 80 dBA, as recorded in a testing project [4], which is less than the Sound Exposure Level (SEL) of 82 dBA for a single transit car traveling at 50 mph at a distance of 50 feet from the receptor [5]. Non-vibrational rock splitting method is used all over the world for urban excavation projects where conventional blasting methods are not applicable. The applications of this method are not restricted to tunneling projects, rather it is used widely for building basement dig out, downtown road construction and expansion, trench excavation, vertical shaft excavation and pipe route construction. While some researchers have worked on different parameters involved in the use of this method, such as the disturbance level due to noise production and the applicability of this method under different geological conditions; there is still lack of research work regarding the excavation mechanism and investigation of fracture propagation in rock due to rock splitting in different rock strength conditions. Furthermore, the constitutive equations involving the relationship between various parameters of non-vibrational rock splitting method are also not available due to lack of research work. An important part of the non-vibrational rock splitting method is the drilling of boreholes that not only takes much time but also produces most of the noise too. The spacing between boreholes depend on the strength parameters of the rock to be excavated.