Articles
Self Drilling Hollow Anchor Bolt Application in Yuxi-Mohan Railway Tunnel
by Anchor S. Web DesignerSelf-drilling anchor bolt is a kind of anchor that integrates
drilling, grouting and anchoring functions together. It can construct in
complex formations with high construction efficiency and good anchoring
quality. Self-drilling anchor support can give full play to
the self-stabilization ability to surround rock, and it is widely used in
tunnel surrounding rock support.
Manmushu Tunnel in Yuxi-Mohan The railway is
located in Mengla County, Xishuangbanna Prefecture, Yunnan Province, with a
total length of 11.6 kilometers and a maximum buried depth of 660m. It is a
high-risk control project for the China-Laos Railway. The surrounding rock is
grade IV-V and is mainly mudstone intercalated with carbonaceous mudstone, and
the groundwater is mainly bedrock fissure water, which is poorly developed and
has a small amount of water. The 30m-buried shallow weathered layer of the
DK431+534-564 section of the tunnel entrance is relatively thick, and the
double-line V-level reinforced type II composite lining is adopted.
In order to solve the problems of difficult
drilling and low construction efficiency of ordinary bolts in special
surrounding rock conditions with more weathered rocks, ZYS113 drilling rigs and
R51 hollow anchor bars are used for construction, and the single-hole drilling
depth is 21m. During drilling, there are 17 holes in each ring at the top of
the tunnel end face. The hole spacing is 400mm, which is inclined upwardly at
an angle of 1-2°. The drilling diameter is 76mm, and each hole is equipped with
3 6m long hollow anchor bars and 1 3m long R51 hollow anchor rods. The
overlapping distance between each pipe roof ring is 3 meters. After drilling,
the hollow anchor bar can be used as a grouting channel for grouting from
inside to outside. The grout is returned from the hole bottom. The grouting
pressure is 0.4MPa, the water-cement ratio of grout is 0.45, and the pressure
maintenance time when the overflows are not less than 10 minutes, which can
realize rapid and full penetration of the grout along the rock mass fissures.
Pressure grouting can ensure that the grout spreading radius is large, and the
surrounding rock will be consolidated into a whole to achieve the purpose of
permanently anchoring the surrounding rock.
Self-drilling anchor bolt has obvious efficiency increase due to its advanced
technology. The average drilling time for 21m holes is 40 minutes, and the
drilling time for each ring of 17 holes is about 11 hours, and the minimum
time is 9 hours. Its economic advantages are obvious.
Self-drilling anchor bolt can simplify the drilling, grouting, and anchoring
procedures. The full length of the bolt is fully anchored, and it can provide a
certain supporting resistance immediately after excavation, effectively
suppressing the loosening and deformation of the surrounding rock, and avoid or
slow down the occurrence of disease accidents during construction and use of
the project. The use of self-drilling anchor bolt and drill
bits can ensure the grouting layer is at least 20mm, which fully guarantees the the durability of the bolts, and is especially suitable for supporting and
strengthening complex formations and broken surrounding rocks.
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About Anchor S. 
Web Designer
8 connections, 0 recommendations, 87 honor points.Joined APSense since, July 30th, 2020, From Beijing, China.
Created on Jul 18th 2021 21:09. Viewed 215 times.
