Lesson 4-Drilling pattern set 3.pptx Lesson 4-Drilling pattern Set 2 .pptx Lesson 4-Drilling pattern Set 1 .pptx Lesson 3 -Tunnel Shafts and its details in tunnel engg.pptx Lesson 1- Introduction tunnel engg for knowing the methods in excavation of tunels.pptx Lesson 2- Tunnel Surveying prior to tunnel construction Drilling in underground excavation method 
