bosh sahifa

Specify rock bolt bearing plates by verifying bolt and washer fit, hole dimensions, material and finish, load evidence, drawing revision, and assembly checks.

When using squeeze support techniques they differ from normal rock bolting practices due to the rock surrounding your excavation will most likely still deform after you have excavated. If you have a weak rock mass with enough stress applied to it. Tunnels and roadways can become subject to large amounts of convergence. Shotcrete cracks and failure of reinforcement can also occur. The excavation will begin to lose width and height.
Using larger or higher capacity rock bolts or stiffer lining's will not solve this problem.
Proper support needs to be designed to accommodate these rock masses and their ability to deform. Based on the situation you can use different types of support such as. Yielding reinforcement, steel supports that can deform. Shotcrete that can be engineered to yield and support being placed at different stages during excavation. As well as monitoring of the deformation.
You want to allow some movement but be able to keep the excavation safe and workable.
Below are some concepts and types of support used when dealing with squeeze and weak rock masses in underground applications.

There are many rock mass classification systems used in underground excavations. Some of these systems can be used to give you a general idea on what supports may be required for your excavation. The RMR and Q-system will allow you to assess the rock mass around you and translate that into numbers and information. They can not provide you with a complete support design for your site however.
When working in underground environments you need to have an understanding on what supports may be used in an excavation. Rock bolts, cable bolts, wire mesh, shotcrete and support are all used to keep your excavation standing.
Using RMR you are given a number and information to go off of to help you design supports for your site. The Q-system will give you more information to go off of as it is made up of different categories and can provide support information for your excavation.

Design of ground support should always start from what rock mass you have in front of you. It should never be based on one rock bolts ability to support ground. There are many types of rock mass that will require different support systems. From competent jointed rock, very broken rock mass, squeezing ground and even rockburst ground.
When designing ground support you want to make sure your system can withstand what type of failure you may encounter. Shape of opening, stresses present at the site, ground water and time the support needs to last.
Classifying your rock mass with systems such as RMR, Q and GSI will allow you to determine how good your ground is. These classification systems should be used along side further analysis and checked at site.
Below we will go into detail about matching rock bolts, cable bolts, self drilling anchors, mesh and shotcrete to your ground conditions.