As a new construction technology, self drilling anchor system has been widely applied in hydroelectric station. It overcomes technical difficulties in loose rock conditions, realizes the primary stabilization by combining jetting cement and drainage hole method.
Self drilling anchor bolt is the main operating unit in self drilling anchor system. It is hollow and has full thread on surface. Coupling is adopted to lengthen it and one-off drill bit is installed on the front end.
Because of special structures, self drilling anchor bolt has following advantages:
1. High efficiency: self drilling anchor bolt combines drilling, grouting and anchoring together, which can be done at the same time, time-saving and high-efficient. Compared with common anchor bolt, it decreases the processes of pulling out of hole, installing anchor bar and inserting grouting pipes, which is quick and simple.
2. High adaptability: It is suitable for stratum which is difficult to drill hole, such as loose and broken surrounding rocks. After drilling holes, anchor bar stays in the hole, which avoids collapse, saves time and reduces construction difficulties. With whole thread on surface, it can be cut at any position. So it is suitable for different construction conditions.
3. High anchoring force and good anchoring effect: The thread of self drilling anchor bolt is generally R-thread or T-thread. They connect with coupling tightly and have good bonding effect with grouting slurry. When grouting, slurry is from the bottom to orifice, full and dense. Grouting quality is good.
Besides, self drilling anchor bolt in high slope of hydroelectric station has other features, such as big tensile pulling force of single anchor bolt, great depth, control or reduction occurrence of rock burst, enhance ability of anti-seismic and control deformation effectively.
On September 8, CRG announced that it had won a railway construction bid for section I, II, and III of the Boten-Vientiane Railway Project (also known as the China-Laos Railway), together with the Laos-China Railway Company Limited in Laos.
For temporary soil nailing, there is no need to use plastic casing. The angle deviation between flat plate or domed plate and self drilling anchor bar is up to 3°. Generally temporary support time for foundation pit engineering is 3-6 months, not more than 24 months.
Malaysia officially launched the Kuala Lumpur LRT3 metro construction project on August 24 at Stadium Malawati in Shah Alam.
The mostly elevated 37.7 km LRT3 line would connect the Bandar Utama and Johan Setia districts in the west of the city. One of the 26 stations would be underground, and five would be interchanges with existing or planned lines. Design capacity is 36 720 passengers/h per direction, and a fleet of six-car trainsets is envisaged, running at peak headways of 2 min using CBTC.
Work is due to begin in early 2017 and is expected to be completed by August 31, 2020.
Soil nail wall provides a cost effective and efficient solution to slope stability and earth retention problems in the tunnel portal reinforcement of metro projects. Its construction process is faster than other similar methods. Metis has rich experience in providing soil nail wall solutions for slope reinforcement, foundation pit support, tunnel portal reinforcement, soil radial reinforcement, railway embankment and road widening, etc.
Soil nail wall has the following advantages:
1. Able to follow irregular curves;
2. Portability for tight spaces;
3. Flexible, easily modified techniques;
4. Installation of soil nail walls is fast and cost-effective;
5. Less noise and traffic obstructions;
6. Minimal impact on nearby properties;
7. Minimum shoring space required.
Sydney’s new metro railway will run through two purpose designed and built tunnels. A number of factors determine the tunnel route and alignment. These include:
1. The location, depth and structure of the stations
2. Vertical track grade
3. Rock conditions
4. Track curvature, to allow train speeds of up to 100 kilometers an hour
5. The physical constraints of the route, including crossing under Sydney Harbor.
Stage 1: Sydney Metro Northwest
Tunneling finished in January 2016 on Australia’s longest railway tunnels–twin 15 kilometer tunnels from Bella Vista to Epping as part of Stage 1 of Sydney Metro.
Stage 2: Sydney Metro City & Southwest
Tunneling will start in 2018 on the twin tunnels for Stage 2, from Chatswood to Sydenham, including under Sydney Harbor and through the central business district (CBD).
Self drilling anchor bar used in tunneling can improve the stability and load bearing characteristics of rock mass. Under the circumstance of weak and broken rocks, self drilling anchor bar technology is an ideal anchoring system for supporting to prevent tunnel collapse, rock deformation, and ensure construction quality and the safety of workers. Metis self drilling anchor bar has been widely used in numerous metro railway projects. Due to the reliable products and strict quality control, Metis has won a general recognition of our tunneling industry clients.
Micropiles are rapidly gaining popularity for foundations in urbanized areas or in locations with low headroom and restricted access. They are an ideal choice for underpinning or emergency repairs because they can be installed in virtually any ground condition with minimal vibration and disturbance to existing structures.
Self drilling hollow bolts are ideal for micropiles, soil nails, and tie down and tie back anchors in difficult ground conditions like weathered and decomposed rock, round gravel, sand and clay soils for either permanent or temporary use.
The use of hollow bars in micropiles has greatly increased over the past ten years. Hollow bar micropile construction, also known as self-drilled, is becoming a popular option because it allows faster installation processes and ground improvement at the same time. Despite the growing demand for hollow bar micropiles, little work has been devoted to evaluating the nominal bond strength between the micropile grout and the surrounding soil, especially in clay soils.
The hollow bar, used as both drill rod and grout conduit, is left in the ground as reinforcing steel to transmit compression, tension, and lateral forces. Hollow bars have a larger section modulus than solid bars which increases their bending capacity. With the continuous tremi-grout injection, 100% grout cover and therefore excellent corrosion protection is accomplished, similar to reinforcing steel in concrete.
Hollow bar micropiles are gaining increasing acceptance by engineers and the industry.