The minimum unbonded length for rock and soil ground anchors is 4.5 m for strand tendons and 3 m for bar tendons. These minimum values are intended to prevent significant reductions in load resulting from seating losses during transfer of load to the structure following anchor load testing.
Longer unbonded lengths may be required to:
(1) locate the bond length a minimum distance behind the critical potential failure surface;
(2) locate the anchor bond zone in appropriate ground for anchoring;
(3) ensure overall stability of the anchored system;
(4) accommodate long term movements.
In general, the unbonded length is extended a minimum distance of H/5 or 1.5 m behind the critical potential failure surface (see section 5.3.2) to accommodate minor load transfer to the grout column above the top of the anchor bond zone.
As a general rule, the anchor bond zone and unbonded zone should be grouted in one stage to maintain hole stability and to create a continuous grout cover for corrosion protection.
However, for large diameter anchors in which the unbonded length of the anchor extends just behind the critical potential failure surface, significant strains at the top of the anchor bond zone may cause load transfer into the grout column above the anchor bond zone.
Large diameter anchors have been grouted in two stages (two stage grouting). With two stage grouting, the anchor bond length is grouted (Stage 1) and the anchor is tested. The unbonded length portion of the drill hole is then grouted (Stage 2) after the anchor is tested.
The two-stage procedure is not recommended since local collapse of the ground can occur which will compromise the corrosion protection provided by the grout.
Metis is a professional manufacturer and supplier of rock anchors as well as high strength bolt system,which located in Luoyang,China,a city with thousand years of history and glorious culture.Metis own two plants,one is sited in Luoyang,the other is in Changzhou,Suzhou province in China,Changzhou plant is near Shanghai,which is the largest as well as the most developed city in China,with convenient transportation and easy collection of raw material.
Metis specialty rock bolts have been exported to more than twenty countries,clients are all speak highly on our featured products like self-drilling bolts,fiberglass rock bolts,large-diameter anchor bar,stainless rock anchors and epoxy anchors.
Metis dill anchor has been widely adopted in complicated loose and broken geological condition,as well as pre-support project,radial support project,slope stabilization,foundation support project,soil nail wall,back pull anchor rod retaining wall and couples of other civil reinforcement works.
What's more,Metis mechanical bolt can be tailored by our global clients,these anchoring products will be cut and connected at any point depending on the specific desire of our customers,so there is no need to worry about the size,it can be customized by you and whatever your post anchor requirements may be we can produce specials on request.
A number of remedial methods can be implemented in thecase of existing buildings, in order to improve their mechanica lcharacteristics. Among the various methods available, the use ofanchor systems is one of the most effective ones.Anchor systems are commonly used in plain or reinforced concrete, as well as for structurally strengthening and retrofittingexisting constructions and for connecting new structural elementsto existing ones.
Using post-installed anchor systems is a very efficient connection technique for structural reconstruction and expansion, and there have been a large number of studies on the behavior of adhesive anchors. Cook studied the data base including 888 European and American tests and developed a better and more user-friendly design model than those existing previously.
An achitect proposed a new failure mode and verified its validity using a worldwide database containing 415 tests.Further, Eligehausen has reviewed the development of adhesive anchors in the United States. Finally, abundant design principlesfor engineers referring to R32.
Metis has achieved the certification of ISO quality control system(provided by BV company) , the whole self-drilling anchoring system has pass the CE certification since 2011.
Our target is to produce first-class anchoring products to service high-end customers globally. Our mission is provide one-stop solution service for clients all over the world. During the production, the workers need to do the first article inspection by themselves and the inspector will do random test for products, all of the inspection data will be recorded.
Our company has its own lab, equipped with tensile testing machine and other testing machines, each batch of goods is provided with the test report from our lab, we can also provide test report issued by third party test organization if needs, such as SGS test report.
And we set up different departments and sections in charge of different business, which include Marketing Center, Sales Center, Technical Center, Luoyang Factory, Changzhou Factory, QC Center, Planning & Management Department, Financial Department, HR Department and Administrative Department.
If you have any question please contact me asap,we have professional service team here to provide drilling solutions for you,you are welcome to visit our company as well as plants.
The self drilling anchor systems range includes self drilling anchor system,self drilling anchor bolt,self drilling rock bolt,self drilling hollow anchor,self drilling anchor and so on.
Metis is committed to the goal of sustainable development and research of anchoring products. We balance social, environmental and economic considerations in how we manage our business.
We believe that operating to leading standards of health, safety and environmental management and engaging with our stakeholders in two-way, open dialogue enhances our business reputation and is a source of competitive advantage.
We comply in full with the laws and regulations governing our business and conduct regular internal and external audits of our businesses and operations to assure compliance with our business principles, policies and standards.
We aim to construct a safe workplace that is injury free, and to enhance the well-being of employees, sub contractors and visitors.
We provide visible safety leadership, and appropriate leadership development and training at every level;
We engage and maintain a positive safety culture, behavior, and awareness;
We provide safe work systems and occupational health and hygiene programs;
We report, manage and learn from injuries, illnesses and high potential incidents.
If you have any question please don't feel any hesitate to contact us at any time,we have professional service team to provide perfect drilling solutions and anchoring measures,we warmly welcome all the groups to communicate and visit,here are experienced team waiting for you!
In order to prevent the deformation and loose of the rocks caused by the application of mining,tunneling,foundation support,hydroelectric project and other civil constructions,forepoling of rock bolt can play a significant role in giving a perfect effect and offering best anchoring solutions.
Excavation and install the self drilling anchor into the rock surface should be processed at the same time,under the protection of temporary loading structure of the stratum,forepoling is well suited to the excavation of soils and rocks.Press concrete or prepare some tendons within the steel pipe to guarantee the grout can be filled sucessfully.
Rock bolt of Metis self drilling anchor can be applied in a great many ground conditions,such as broken rocks,loose soils,low-buried tunnel and fracture zone.In general,the thickness of steel pipe is 10-30mm and the diameter of anchor bar is 80-180mm.
If you have any question please don't feel any hesitate to contact us at any time,we have professional research&development group here to provide drilling service and reliable and practical placing solutions for you!