Study on engineering characteristic and mechanism of compression type ground anchor in granite residual soil

In the granite residual soil, 28 compression type ground anchor were made according to the engineering methods, the load tests of anchor and distributed fiber tests of grout were carried out. The results show that: (1) In the process of transferring load from the top of grout body to the bottom, the load loss occurs due to the tunnel resistance.(2) The apparent critical anchoring length is about 12m, the ultimate bearing capacity is proportional to the grout length within 12m, and after 12m it increases slowly.(3) The grout strain can be divided into front, middle and back sections. The back section is subjected to the pressure of the bearing plate and produces the compressive strain; the middle section is subjected to the tunnel resistance and the tensile strain is the main strain; the front section is affected by the overflow grout and produces the sudden increase of the tensile strain.The strain difference of middle and back section characterizes the bond stress.(4) Compared with the fully bonded anchor, the bearing capacity of the compression type anchor under the same conditions is lower, the variation degree is larger, the compressive strain distribution range is smaller, and the peak value is lower.(5) The measured ratio of elastic deformation is positively correlated with the load and negatively correlated with the tendon free length.(6) The measured stiffness coefficient is greater than the theoretical value, which is negatively correlated with the load level and roughly tendon tree length.(7)Elastic-plastic ratio is negatively correlated with the tendon free length.