Hollow bar micropiles are becoming a popular option for foundation retrofitting because of their fast installation and effectiveness as both a foundation system and ground improvement at the same time.

Self drilling hollow grouting bolt is made up of drill bit,hollow rod body,anchor plate and anchor nut.It is mainly used for the supporting engineering in the loose and broken rock strata with difficult to drilling hole.Different is available to cater for the different rock strata condition.

A variety of types and diameters of sacrificial cutting head / drill bits are available for installation in varying subsurface conditions. The grout to ground bond stress is directly proportional to the drill bit diameter, so proper bit selection is critical both for installation and for optimizing hollow bar micropile capacity.

The Sinorock hollow-bar micropile is a composite monolithic structure of micro alloy steel and high-strength cement grout. The hollow steel bar has a continuous external thread running the entire length of the bar and is advanced under rotation and possibly with some hammering action in very stiff or hard soils. As the bar is advanced,the grout is injected through the hollow bar and out through the sacrificial cutting head.

Since the outside diameter of the cutting head is typically 1 to 4 times larger than the outside diameter of the bar, the grout (under pressure) will flush the drill cuttings to the surface through the cavity along the outside of the bar and the wall of the excavation created by the cutting head.

Hollow Bar Micropiles have emerged since the early to mid 1990’s as an economical system for installation primarily in soils. This type of micropile is easily installed in low headroom or restricted access applications and exhibits high unit load capacities coupled with superior stiffness performance compared to conventional drilled and grouted ground anchors without the need for temporary or permanent casing.

In order to solve the problems of steep— inclined limestone,poor self support capability of weak and soft shale and difficulties in the control of the rock mass deformation in the construction of the underground powerplant of Pengshui hydropower station,the new technology of expansion and prestressed type hollow grouting bolt with steel wedge is adopted to reinforce the shallow— covered rock mass.The anchor piers with steel plates,which are used to replace the original concrete anchor pier s,can simplify the construction technology,ensure the construction quality and enhance the construction speed.Thus,the wall rocks are deeply and immediately anchored and the deformation risks of the wall rocks are minimized.The comprehensive application of the new anchoring technology ensures the shallow and/or deep anchoring quality in soft and weak shale.In addition,the new technology results in significant economic and social benefits and can be popularized.

Sinorock is recognized for its excellent quality, delivery performance, innovative management and perfect service system. In addition, many products we have developed have become industry standards. The products we are provide all kinds of self drilling hollow bar and the corresponding accessories. Our self drilling hollow anchor bolt products received the consistent high praise by the customers. Till now, Sinorock has become one of the famous self drilling hollow bar suppliers.

Micropiles have the advantage of quick construction

posted on 15 Sep 2017 09:27 by hollowbar

Micropiles, also called mini piles, are often used for underpinning. They are also used to create foundations for a variety of project types, including highway, bridge and transmission tower projects. They are especially useful at sites with difficult or restricted access, or with environmental sensitivity. Micropiles are made of hollow bars or steel rebars with diameters of 60 to 200 mm. Installation of micropiles through top soil, sand and cobblestones overburden and into soil rock can be achieved using Air Rotary or Mud Rotary drilling, impact driving, jacking, vibrating or screwing machinery.

Advantages of Hollow Bar Micropiles
Fast one-step installation
Simultaneous drilling and grouting
Allows the use of smaller equipment at lower cost
Allows low overhead, limited access installation
Improves the ground (densification)
Offers higher skin friction

Where can a micropile be utilised?
Micropiles have the advantage of quick construction, small-sized equipment required and economy, etc. It can be used in every kind of construction in basic foundation, retaining wall and water-proof wall. The unique characteristics of micropiles and the equipment that installs them means there is more flexibility than all other type of foundation system. Micropiles can be installed in all conventional applications in addition to numerous other locations where conventional equipment would make the project impossible, some of these are;
Limited access situations
Difficult access situations
Environmentally sensitive projects
Resisting Uplift and Dynamic Loads
Underpinning
Upgrading or increasing the capacity of existing foundations
Emergency repairs
Seismic Retrofit
Structures affected by adjacent excavation, tunneling or dewatering activities
Slope stabilisation and land/rock falls
Excavation support
To provide a fast, effective alternative to more traditional methods

Are micropiles suitable for all geotechnical conditions?
Micropiles can be utilized in more geotechnical conditions than any other type of pile. This can achieved through the application of different drill bits for different soil or rock profiles that are encountered. If the geotechnical conditions vary from conditions anticipated via testing, you just need to change the drill bit, not the installation procedure or design ensuring the project maintains momentum.