मेलम्ची सुरुङ्गमा Rock dowel drilling, grouting र  installation गरिदै गरेको अवस्था
Channel: Pusker
Date: 2020-12-10

Rock bolts and rock dowels are threaded steel bars that are used to secure potentially unstable blocks on the face of a rock cut.  The process involves drilling through the unstable block and into more competent rock beyond the failure surface. The steel bar is then inserted into the hole and grouted into place using a cement based grout. In some applications, only the bottom portion of the rock bolt is grouted to create a bonded and un-bonded zone. This allows for the rock bolt to be tensioned against the unstable block resulting in active pressure to hold the mass in place.  In rock dowel applications, the borehole is fully grouted surrounding the steel bar, resulting in static pressure to hold the mass. Ameritech has some of the most specialized rock drills in the industry which gives us the ability to install rock bolts and rock dowels in locations that would normally be impossible to access.Rock dowels are passive reinforcing elements which need some ground displacement for activation. In installation of rock dowels, a hole is drilled and unmentioned steel bars are inserted into the hole. When displacements along joints occur, rock dowels are subject to both shear and tensile stresses. The level and ratio of shear and tensile stress depends on the properties of the surrounding ground, the grout material filling the annular gap between the dowel and the ground and the strength and ductility parameters of the rock dowel itself. Moreover, the degree of dilation during shear displacement affects the level of stress acting within the dowel.Rock bolts are pensioned once the anchorage is attained to actively set up a compression force into the surrounding rock. This axial force increases the shear capacity and is generated by pre-tensioning of the bolt. The system requires a bond length to enable the bolt to be pensioned. In essence, rock bolts start to support the rock as soon as they are pensioned and the rock does not have time to start to move before the rock bolt becomes effective.

Drilling for curtain grouting work-Curtain grouting को लागि drilling गर्ने तरिका
https://youtu.be/-LlxWnZEcEQ