Research On The Horizontal Load-bearing Behavior And Mechanism Of Root Pile Foundation

Due to the uneven distribution of power resources in my country,mainly concentrated in the western region,and the country’s economic development center is on the southeast coast,a large-span dispatch of western power is needed to support the eastern part.The original transmission line tower foundation is no longer suitable for UHV transmission lines.Since large construction machinery cannot enter the construction site,the digging foundation is suitable for mountainous terrain and has good economic and environmental benefits.Horizontal load has a great influence on the bearing capacity of pile foundations,so it is necessary to study the horizontal bearing characteristics of excavated root pile foundations.This paper will combine field tests,transparent soil model tests and numerical simulation experiments to analyze the horizontal bearing characteristics of the root pile foundation and the stress mechanism and failure mode of the root pile under horizontal load,as well as the effect of different root arrangements on the horizontal bearing characteristics.influences.The analysis mainly draws the following conclusions:(1)Analyze the field test,the horizontal bearing capacity of the root pile>the expanded bottom pile>the constant-section pile,the root pile can greatly increase the horizontal bearing capacity;analyze the soil resistance coefficient m,the proportional coefficient is larger when the horizontal displacement is small.The soil resistance of the soil around the pile is small.As the horizontal displacement increases,the proportional coefficient decreases,and the soil resistance of the soil increases and gradually reaches the maximum value;the bending moment of the test pile first increases and then decreases with the pile body,at 4.0 The bending moment around m is the largest,and it is 0 at 9m;the combined loading test shows that the vertical load reduces the horizontal bearing capacity.(2)The transparent soil model test solved the problem of invisibility of the soil around the pile.The bearing characteristics of different root arrangements and the distribution of the soil displacement field around the pile are analyzed,and the horizontal bearing capacity is the largest when the number of layers of the upper root is 3 and 4;the vertical load increases the soil around the pile The disturbance reduces the earth pressure and therefore reduces the horizontal bearing capacity.(3)In the numerical simulation experiment,the cross-section size,number,length,layer spacing and multi-layer root bonds are analyzed.Among them,the size,number and length of the root have no effect on the horizontal bearing capacity of the root pile.The depth of the first layer,the layer spacing and the number of layers have a greater influence on the horizontal bearing characteristics of the root pile.A reasonable design can greatly improve the root pile.The horizontal bearing capacity of the pile;the optimal design to obtain the horizontal bearing effect: the cross-section size is 150×300mm,6 pieces are arranged at equal intervals,the exposed length is 600 mm,the first layer is buried 1d,the layer spacing is 1d,and the root is 3 layers.(4)Combining the transparent soil model test and numerical simulation test,the force mechanism of the soil around the pile and the force mechanism of the root pile;the horizontal load on the top of the pile is transferred along the pile body to the lower part,and the soil around the pile is subjected to the pressure.The pressure deforms downwards,and the soil around the tensioned side pile receives the tensile force from the root,so that the pile-soil interaction is in a balanced state.According to the numerical simulation test,the force mechanism of the root pile during the entire stress process is analyzed.The body bears most of the horizontal load,the root bears the greatest tensile stress and compressive stress,and the upper surface of the compressed side root is subjected to pressure and the lower surface is subjected to tensile force,and the upper surface of the tensile side root is subjected to tensile stress and the lower surface is subjected to compressive stress..(5)The damage of the root pile can be divided into the soil damage around the pile and the root damage.The failure characteristics of the root pile cause the test pile to produce cracks and the concrete exits the work.The soil around the pile is characterized by different crack widths and lengths on the surface.The damage of the root is mainly manifested in the connection position of the root and the pile body.The separation of the root and the pile body produces more cracks and the concrete protective layer falls off.The above situations can be considered as the root pile damage.