Research On Mechanical Characteristics Of Expansion Control Anchor Based On Soil Anchor Interaction

Geotechnical anchoring technology is widely used in various slope projects,dam foundation projects,and deep foundation pit projects.As a new type of support technology,the design and development of expansion control anchors provide a new idea for Geotechnical anchoring technology.The expansion control type anchor rod uses the inflation pressure of the rubber bladder to exert a squeezing force on the soil around the anchor,thereby generating a friction effect;in this process,the soil around the anchor is subjected to confining pressure to form an effective reaction force.Based on the combined action of the soil anchor,an active and passive protection system is formed,which effectively enhances the stability of the support system.However,the research and use of expansion control anchors are in their infancy,and a series of mechanical mechanisms such as the anchoring force composition,soil stress field,displacement field distribution law,and mechanical characteristics of soil anchoring surfaces need to be further studied.Therefore,in this paper,the mechanical characteristics of the expansion control anchor are analyzed and studied in detail from the aspects of field test,mechanical mechanism and finite element numerical simulation.First of all,according to the basic fixed anchor structure at this stage,the interaction between the components is discussed and summarized,and the working mechanism and mechanical relationship of each anchor device are obtained.On this basis,the field pull-out test of the anchor was carried out,and the relationship curve between the bearing capacity and displacement of the anchor under different inflation pressures was obtained.The results show that,during the anti-pulling process of the anchor,according to the different bearing capacity development range,the mechanical behavior process can be divided into: linear elastic stage,nonlinear elastic stage and plastic stage.The ultimate bearing capacity of the anchor increases linearly with the increase of the inflatable pressure,and the increase of the maximum displacement increases significantly with the increase of the inflatable pressure,which exceeds the bearing capacity.Based on the analysis of traditional anchor anchoring force,combined with the actual engineering structure of the expansion control anchor,the analysis of its anchoring force composition is as follows: end support anchoring force,tension anchoring force,expansion anchoring force.Based on the theory of elastic mechanics,the mechanical expressions of the anchoring forces of the expansion control anchor in the soil layer are derived,in which the tension anchoring force is positively correlated with the expansion anchoring force.On this basis,based on the structural characteristics of the expansion control anchor,a simplified force model was established under the conditions of reasonable assumptions.Finally,according to the simplified stress model of the expansion control anchor,the numerical simulation study of the anchor's pulling resistance process was carried out by ABAQUS finite element analysis software.The load and displacement curves were basically consistent with the field tests,and the rationality of the numerical simulation was verified.The numerical simulation results show that the axial stress distribution in the anchorage section of the anchor has a certain rule,and the forces acting on the contact surface of the anchor are normal stress and friction-shear stress.The relationship between the two stresses basically satisfies the rule presented by the mechanical expression.Based on the analysis of the law of strain in the surrounding soil,the distribution of stress and the law of stress migration in the soil layer are summarized.The method of controlling variables was used to compare and study the stress field,displacement field distribution law and anchoring effect of expansion control anchors and surrounding soils under different inflation pressures,different embedding depths,different soil parameters and ground overload conditions.The mechanical properties of the anchor under different conditions were explored.