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.
Self drilling hollow bar’s designed tension is mainly depended by possibility, reliability and convenience of construction technique.
If tension designs too big, accordingly, the cross section and gravity are big, then it is difficult for inserting into hole and construction quality cannot be guaranteed, also it’s not easy to handle if tension test and validation test have problems; if tension designs too small, the amount of hollow anchor bolt should need many and the price costs high.
After confirming self drilling hollow bar’s tension, the design of cross section should depend on the design method of tensile bar, at the same time, the demand of construction should be readjusted if necessary.
The hollow anchor bolt’s head coupling should be designed basing on the principle design of prestressing force.
After confirmation of hollow anchor bolt, it’s necessary to calculate structures’ stability. If stability of structures can’t reach demand, the design of hollow anchor bolt should be reconsidered even if the design of every part of anchor bolt is reasonable and economic. Lengthening hollow anchor bolt, calculating again and consulting relevant calculation method to ensure stability of soil and rock, quality of projects.