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.
Metis® self drilling anchor is a hollow anchor, having the new integrated functions of drilling, grouting, and anchoring. It has the extended feature because self drilling anchor bolt can be lengthened by using coupling. It can be applied in the basement, under the bridge, the river, and a narrow construction environment, and now widely used in tunnels, mining, slope and other projects. It is suitable for hole collapsed areas and disease treatment, such as, reinforcing existing structures, grouting and filling cracks, etc. There are two specific cases in this article about the applications of self drilling anchor to illustrate the reinforcement effect.
Case 1. Beijing-Qinhuangdao Expressway slope reinforced with self drilling anchors
The slope is very unstable because rock fractures with a layer of mud and expansile kaolin are easy to expand and spall by rain, which has poor resistance to weather. It has achieved good effect in three years after using the reinforcement method of a self drilling anchor and jet anchor net. Click here and learn more.
Soil nailing wall supporting is a new type of retaining structure for the excavation and slope stability in recent years developed. The technology is from the 1970s, nearly 30 years’ history. The first application of soil nail wall supporting in the engineering was in France,1972. The first application in the USA was in 1974 and Germany in 1979 firstly built a permanent soil nailing works. The earliest application in China was probably in the slope stability engineering of Liuwan Mine, Shanxi province in 1980. Compared with foreign countries, China’s development in the soil nail wall supporting technology also has some unique achievement, mainly in the following aspects:
1.Soil nail wall combines with waterproof curtain, which emerges a kind of water-stopping soil nail wall.
2. It develops a type of soil nails into the grouting for the hole, difficult to hole in sand and soft soil layer.
3. It develops the technique of combining soil nail wall with prestressed anchor, namely self drilling anchor bolt.
4. Fore reinforcement is developed for the poor excavation of the soil and short self-stabilization.
5.It exploits the simple, economical construction method of Metis® self drilling anchor bolt.
With the increase of self drilling anchor density, strength coefficient is also increasing. When self drilling anchor density is constant, the degree of enhancement of self drilling anchor residual strength is greater than the degree of enhancement of the rock peak intensity. It can effectively improve the mechanical parameters of the original rock. And with the increase of self drilling anchor density, self drilling anchor peak can be significantly improved. Furthermore, it can effectively reduce the plastic zone of surrounding rock, broken radius and displacement of roadway to maintain surrounding rock stable.
As we know, it is inevitable to tunnel in the construction of railways, over the mountains. Given the support role of self drilling anchor in the surrounding rock,Metis® self drilling anchor is often used in the following aspects：
· Stabilization of tunnel portals
· Face stabilization
· Root piling
· Radial systematic anchoring
African Development Bank provided 300 million dollars to support Nacala railway and port project. It includes a deepwater port, a 912-kilometer railway from Mozambique to Malawi, a coal station and a 29.3-kilometer railway connecting the existing railway lines with coal station. It belongs to regional project and aims to promote economy growth and integrative development in Mozambique, Malawi and other countries.
Mozambique Nakala Corridor is an important railway connecting Moatize Mine of Tete Province with Nakala Port. The overall length is 912 kilometers and it passes through the interior of eastern Africa region, such as Malawi and Zambia, etc. Because of rich mineral resources, it is also the main artery of transporting agricultural products and resources products. Not long ago, a world-scale oil-gas field was discovered at offshore area of Mozambique.
The construction and acceptance standard is SATCC, construction technology standard adopts manually laying track. The main work includes subgrade earthwork, culvert, drainage and protection, slope greeting, track construction and so on. All workers united together and overcame difficulties during the process of construction, which lays great foundation for normal railway.
Security, quality, construction period, cost and environmental protection are five essential factors during construction. While self drilling anchor bolt as a new supporting technology, has been used in several projects and fields. It combines drilling, grouting and anchoring together, which is high-efficient, time-saving and energy-saving. Self drilling anchor bolt adopts different materials and then it has different functions. The common one is to support and reinforce project by fastening self drilling anchor bolt with surrounding rocks.
December 22, 2015, Guinean government held grand foundation stone laying ceremony for Souapiti Hydroelectric Station. There were more than 1000 people attended this activity.