Studies On Interface Mechanical Properties And Bearing Capacity Of Cement Mortar Anchor In Loess Stratum

Bolt is widely used in northwest loess region because it can effectively improve soil stability and limit soil displacement.At the same time,due to the concealness of the project and the complexity of the interface,the theoretical research of soil bolt should lag behind the practical application,and it is difficult to provide a more accurate basis for the design and construction of soil bolt in the corresponding loess area.Therefore,this thesis studies the mechanical properties of anchorage interface and anchorage force of anchor bolt in loess stratum from the following aspects:(1)The distribution and development law of anchorage force of anchor bolt in loess were analyzed through indoor tensile test of anchor bolt.Based on interface bonding slip model,anchoring equilibrium condition and deformation condition,the distribution and development law of anchoring force of bolt are explained,and the influence of grouting cracking phenomenon during drawing test is briefly analyzed.(2)The rough anchorage interface was constructed based on fractal theory.the stress and field displacement field of rough interface between the loess and structure during the relative sliding process was analyzed by ABAQUS numerical simulation software,revealing the action and evolution mechanism of the anchorage interface.Based on the interfacial shear tests between structure and loess,the relationship between shear stress displacement and strength characteristics of soil under interfacial and direct shear conditions is analyzed.On this basis,combined with the structural characteristics of undisturbed loess,a mechanical model of bonding and sliding between soil and anchorage interface is established;(3)Based on the knowledge of material mechanics and the theory of reinforced concrete design,the influence of grouting cracking on the tensile deformation of anchor solid is analyzed,and a mechanical model describing the axial tensile behavior of anchor solid is established.On the basis of the interface bond slip model constructed,the theoretical calculation method of the anchorage force of soil bolt considering the grouting body cracking is obtained,and the reliability of the model and calculation method is proved by an example.(4)Combined with the interface model,FRIC custom subroutine was used to simulate the interface mechanical action between anchor solid and soil,and a suitable single anchor drawing numerical model was established.The effects of anchoring length,free section length and anchoring diameter on the bearing capacity and drawing curve of anchor were analyzed by ABAQUS numerical simulation.The following conclusions are drawn: the bearing capacity of bolt increases nonlinearly with the anchoring length.The longer the anchoring length is,the less significant the increase of the bearing capacity of bolt is.The increase of anchoring length cannot improve the ability of bolt to limit the horizontal displacement of structure.The free section has no effect on the bearing capacity of the bolt,but the long length of the free section due to the deformation of the free section is not conducive to the ability of the bolt to limit the horizontal displacement of the structure.The increase of anchoring diameter can effectively improve the bearing capacity of bolt and limit the horizontal displacement of structure,but the effect of group anchoring effect should be paid attention to.