The invention provides a method of constructing a ground anchor, wherein the method comprises performing an introduction step for introducing the boring tool into the ground along a boring axis (F) so as to form a top portion (C1), the mixer device being in the retracted position during the introduction step; then performing a mixing step during which the mixer device is taken to the deployed position and the boring tool is driven in rotation with the mixer device (14) in the deployed position while moving the boring tool axially along the boring axis and while injecting the fluid so as to perform mechanical in-situ mixing of the ground in place with the fluid, thereby forming a bulb (B) in the ground under the top portion (C1), which bulb has a second diameter (D2) that is greater than the first diameter (D1); inserting a reinforcement into the bulb, whereby a ground anchor is obtained.