Stability of tunnel face is important at weak rocks. Steel pipe umbrella arch have very important application in recent years. Umbrella arch constitutes an artificial shell to make tunnel face stable thereby contributing tunnel face safety. It is seen in applications and researches that 2 and 3 inches diameter steel pipes can be used instead of general used 4 inches. steel pipes. Sufficiency of the patterns of pipes can be analyzed by numerical modelling. This research compares numerical modelling data with the field data which is obtained from application of different size steel pipe umbrella arch in different weak rock mass condition.