| Inflatable expansion control anchor is a new type of friction anchor,which is developed on the basis of the original inflatable anchor prototype.The final inflatable expansion control anchor is composed of extruded steel sheet,rubber air bag,power transmission tie bar and control pipeline.Its working principle is mainly to apply pressure to extruded steel sheet by inflatable expansion of rubber air bag,so that the extruded steel sheet contacts with surrounding soil and extrudes,and the anchoring capacity is generated by contact friction between extruded steel sheet and soil.Compared with the traditional grouted anchor,which is widely used at present,it has the advantages of green environmental protection(no grouting),large bearing capacity,stable performance,detection and control of anchoring force,complete recovery,and large residual strength after damage.Therefore,the inflatable expansion control anchor will have a broad application prospect in the future practical engineering application.As a kind of friction anchor,the friction resistance between the extruded steel sheet and the surrounding soil is an important part of the pull-out bearing capacity of the anchor.There are many factors affecting the friction resistance,among which the interface between the extruded steel sheet and the soil is an important factor.At present,when calculating the ultimate pullout bearing capacity of the inflatable expansion control anchor,there is no relevant regulation on the influence of the contact surface between the soil and the extruded steel sheet,and there are many factors affecting the friction coefficient between the extruded steel sheet and the soil.Therefore,in this paper,in view of the shortcomings of the research on the soil extrusion steel sheet in the development process of the inflatable expansion control anchor,the following aspects are studied:(1)Firstly,based on the structure of inflatable expansion control anchor,the stress principle is analyzed.Aiming at the thickness of the extruded steel sheet and the contact surface between the surface and the soil,the thickness,surface texture and surface roughness of the extruded steel sheet are analyzed in detail.Finally,based on the characteristics of extruded steel sheet,the state of contact friction between the sheet and soil is analyzed,and several kinds of extruded steel sheet are put forward and manufactured.(2)According to the different types of extruded steel sheet,it is divided into seven test groups,and the anchor pull-out test is carried out in the field silty clay,and the following conclusions are drawn: increasing the thickness of extruded steel sheet can improve its rigidity,which makes the steel sheet not prone to bending deformation when the air bag expands,so as to improve its pull-out bearing capacity;processing serrated thread on the surface of extruded steel sheet increases the contact area between steel sheet and soil The friction coefficient between the steel sheet andthe soil is increased,and the pull-out bearing capacity is increased.(3)Based on the test data,the pull-out force displacement curve of the inflatable expansion control anchor under different characteristics of soil extrusion steel sheet is obtained,and the change rule of the anchor under different inflation pressure is obtained,that is,the inflatable expansion control anchor is in the elastic stage before reaching the ultimate pull-out bearing capacity,and the pull-out force displacement has a certain linear relationship;after reaching the ultimate pull-out bearing capacity,the anchor and Without rapid failure,it still has a strong anchoring ability,that is,the inflatable expansion control anchor has a high residual strength.(4)The simplified mechanical model of the inflatable expansion control anchor is established,and the shape of the anchor after expansion is simplified to an elliptical cylinder.Based on the spherical hole expansion theory,the calculation formula of the anchoring force of the anchor under different types of soil extrusion steel sheet is derived.At the same time,the theoretical calculation value is compared with the test data to verify the accuracy of the formula,and some suggestions are put forward for the application of the anchor in the actual project by analyzing the pull-out performance of different extruded rigid pieces. |
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