Abstract: The proposed Yunnan Yongde 220kV power transmission project site was geologically and geotechnically investigated. Based on the site conditions, laboratory test results and site bearing capacity class, the transmission tower foundation strengthening program utilized the pressure grouted ground anchors. The test results indicate that the ground anchor was stable after the loading and no strain softening and pullout failure were observed. The pressure grouted ground anchor can effectively strengthen the foundation. At the later stage of the loading, the strain rate was reduced to zero. The deformation zone underneath the foundation was limited to 6 meters below the footing. The maximum deflection at the bottom of the ground anchor is less than one millimeter, indicating a satisfactory result. Compared with the conventional reinforcement method, this method can meet the restrictive requirements of the field construction, the construction process is not only simple and efficient, but also is very cost effective.

Key words: laboratory tests of soil and rock samples, ground anchors, grouting, foundation reinforcement