History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c12.s1.t13.9

v1.c12.s1.t13.9

The problem of roof support at Zawar was simple as the rock is fairly uniform in quality and of high competency. At depth where the rocks are much less weathered, the arched openings are much larger than earlier higher working, and spans of flat roof are up to 20-30 m. Many pillars have been removed by retreat working, in a systematic manner, allowing the maximum depth to be achieved at the earliest with less risk or rock instability and water inflows. At Rajpura-Dariba where rock is weak, large timbers have been used to support both the wall and the roof; and stemples and props seem carefully shaped for the purpose.