Analysis of influencing factors for uplift force of self drilling anchor
The diameter and length of anchor are the factors that affect the pulling force of the self drilling anchor, but it can be controlled by the drilling machine, the length of the self drilling anchor bolt and the drill bit, which is not the main factor for the construction control.
In soft rock or weathered rock layer, the shear strength of the anchor hole wall is generally lower than the bond strength of the mortar to the steel tie rod. Therefore, the ultimate pullout resistance of the bolt in soft rock and weathered rock layer is controlled by the shear strength of the borehole wall. Drawing from the existing experimental data show that the limit of soft rock and weathered rock uplift force is big, the most factors of the pull-out strength is affected by many conditions and geological (such as rock properties, buried depth, groundwater, drilling process, different grouting methods) . Increasing the bond strength between grouting and soil is the key to ensure the uplift of self drilling anchor.
The formation conditions can not be changed, but to improve the bond strength between grout and rock, which can be control from these two aspects of hole cleaning quality and grouting quality.