Uplift Behavior of Shaft Tension Anchors in Stratified Soil

This study performs a numerical analysis on tension-type friction anchors in stratified soils using the strain-hardening-softening and volumetric dilatancy model “SHASOVOD” in conjunction with the FLAC2D software, and verifies the accuracy of the numerical results by field test results. The numerical results show good agreement with the field test results. The numerical results also demonstrate that simplifying the stratified soil into a single-layer soil model to calculate the anchorage capacity does not introduce significant error. In stratified soils, it is recommended to use a double protection measures for the ground anchors to prevent the cement grout body from cracking, which could lead to strands corrosion and affect the long-term anchorage capacity. The anchorage capacity of the ground anchor increases with the SPT-N value, overburden depth, and anchor fixed length. Among these factors, increasing the fixed length of the anchor has the most significant effect. For ground anchors with a 12 cm diameter, the increase in anchorage capacity per unit length of anchor fixed length is approximately 45 kN/m. The load in tension anchors transfers from the anchor top to the anchor bottom, and when the fixed length exceeds 30 m, the surrounding soil friction stress of the ground anchor will experience progressive yielding. Therefore, increasing the anchor fixed length no longer effectively increases the anchorage capacity.