Construction method for rapidly measuring fastening force of low-prestress anchor rod

The invention relates to the technical field of tunnel primary support, in particular to a construction method for rapidly measuring the fastening force of a low-prestress anchor rod. The anchor bearing plate with the groove shape is improved, the strain line of the dynamometer penetrates into the anchor bearing plate, the instrument is started, the strain gauge with the strong magnetic suction head can be attached to the anchor rod, the strong magnetic suction head is made of a high-resistance and low-current material, and is convenient to use, durable, convenient to install and capable of directly measuring the fastening force of the anchor rod; instant and accurate control of mechanical indexes of the anchor rod on site is realized; after the construction is finished, the detection work is also finished, then the power supply of the dynamometer is turned off, the strain gauge with the strong magnetic suction head can naturally fall off, the disassembly is convenient, and the next anchor rod construction ca