Research On Installation And Pull-Up Of Screw Anchors In Sand

Screw anchors are easy to construct,have little impact on the environment,and have good resistance.They have been widely used in various projects such as slope stability,bridge support,and foundation foundations.The installation torque of the screw anchor is a key parameter for selecting reasonable construction machinery and ensuring efficient installation.In engineering practice,the installation torque multiplied by the torque correlation coefficient is often used to estimate the pullout bearing capacity of the screw anchor.Therefore,it is of great academic and practical significance to study the installation and pull-out characteristics of helical anchors.In this paper,through model test and numerical simulation,the influencing factors of screw anchor installation torque and uplift bearing capacity are studied,and the relationship between installation torque and uplift bearing capacity is analyzed.The number and size of anchor blades,soil strength parameters and other factors are studied.Influence.The main work and conclusions of this paper are as follows:（1）The single-leaf and double-leaf screw anchor installation and uplift model tests were carried out,and the influence of the number of anchor leaves,the spacing between the anchor leaves and the installation depth on the installation torque and uplift bearing capacity of the screw anchor was analyzed.The test results show that the installation torque of the doubleleaf screw anchor is about twice that of the single-leaf screw anchor;but the pull-up bearing capacity does not increase linearly with the number of anchor leaves,and the uplift bearing capacity of the double-leaf screw anchor is higher than that of the single-leaf screw anchor.1.07～1.22 times;the installation torque and the uplift bearing capacity of the single and double-leaf helical anchors are approximately linear changes.（2）Based on the finite element software ABAQUS,the coupled Eulerian-Lagrangian method（CEL method）is used to establish the screw anchor installation and uplift model,and the model test and literature data are compared and verified.The results show that the established CEL numerical model can reasonably and reliably analyze the installation and pullup characteristics of the helical anchor.During the rotating installation,the soil is mainly damaged by rotational shearing along the edge of the anchor blade.Under the action of uplifting load,the failure mechanism of the screw anchor is mainly related to the burial depth of the anchor blade.When the installation depth is shallow,the failure surface is mainly vertically upward along the edge of the anchor leaf;when the installation depth is deeper,the failure surface is a curved surface confined around the anchor leaf.（3）Using the verified numerical model,the parameter sensitivity analysis of the installation and pull-up characteristics of the real-size double-leaf helical anchor was carried out.The relationship between the forces is given,and the variation law of the torque correlation coefficient is given.The finite element software was used to carry out numerical simulation under different parameter conditions to analyze its influence on the torque correlation coefficient（Kt）.Numerical analysis shows that the Kt of the double-blade helical anchor decreases with the increase of the anchor blade diameter and the friction angle in the soil,increases with the increase of the dilatation angle,and also increases with the increase of the blade spacing,but the increase is not large.Between installation depth H=4D～10D,the range of torque correlation coefficient Kt is 2.4～10.7.