Long Term Deformation Characteristics Of PVC Sheet Pile Retaining Structure Research On Design Method

With the rapid development of today's society,the momentum of construction in all walks of life is growing stronger.Under the call of the national sustainable development policy,"energy-saving,environmental protection,practical and efficient" has been more and more people's consideration and attention.Green environmental protection building products are to meet the people's ecological environment protection needs,"plastic instead of steel" and "plastic instead of wood" has become a global trend of material selection.In today's society of rapid construction,piles,as the retaining wall of sand-retaining soil,water-retaining and seepage-proof wall,building and other basic structures,play an important role in various fields.However,the traditional pile technology,complex,time-consuming,durable,weak structure,compared with PVC sheet pile,is a fast,efficient,environmentally friendly pile foundation form,with a light material,high strength,water resistance,flame retardant,anti-aging,corrosion,anti-ultraviolet,durable,installation and disassembly method It is simple and has long service life.Therefore,the study of long-term deformation characteristics and design methods of PVC sheet pile supporting structure is an important project of epoch-making significance for construction projects.In this paper,based on the experimental data of PVC materials made by Taiwan Laboratory of China and the method of numerical simulation,the research results are as follows:(1)The mechanical properties of PVC sheet piles and steel sheet piles were compared and analyzed on the basis of the experimental reports of PVC materials in Taiwan laboratory and relevant foreign data.The density of PVC is about 1/6 of steel density,that is,PVC is 6 times lighter than steel,but the tensile strength of PVC is about 1/10 of steel,10 times weaker than steel.The tensile modulus is about 1/80 of that of steel.For a given load and section size beam,the flexure of PVC material is about 80 times that of steel.But the cost of steel sheet pile and reinforced concrete sheet pile is high,the cost of manpower and machinery is easy to corrode;from the economic point of view,the cost of traditional technology is 2/3 or even lower;without land expropriation,the influence of construction team is small;the construction efficiency is more than five times that of traditional technology.(2)The maximum excavation depth of PVC sheet pile cantilever support is 2.5m and the minimum pile length is 6.7m.The maximum lateral displacement of PVC sheet pile is 12.7 m m,the maximum surface settlement outside the pit is 11.8 m m,and the maximum bending moment is 10.78 kN.m/m.It is concluded that the normal stress at the maximum bending moment is 2.57 MPa,while the yield strength of PVC sheet pile is 90.07 MPa and the strength of PVC sheet pile is 2.9%.The result of reduction is usually conservative,and the safety factor of foundation pit is 1.674 under the most unfavorable conditions,which meets the requirements of the code.The variation trends of lateral displacement,surface settlement and bending moment of PVC sheet pile and steel sheet pile under different working conditions are compared and analyzed.The results show that PVC sheet pile can effectively replace steel sheet pile under certain conditions.To carry out foundation pit support.(3)Taking the classical clay foundation pit excavation simulation as an example,by changing the support form of PVC sheet pile to cantilever and single support,and the excavation environment of foundation pit to water and no water,four design schemes are obtained.One scheme is no water cantilever support,the other is water cantilever support,the third scheme is no water single support,the fourth scheme is water sheet support.Supporting support.By changing the cohesion and internal friction angle of the soil,the combined numerical simulation analysis was carried out.The first study concluded that:in the case of PVC sheet pile cantilever bracing structure system in anhydrous clay foundation pit excavation,the internal friction angle remained unchanged,and the maximum excavation depth gradually increased with the increase of cohesion parameters.When the internal friction angle is 35°,the maximum excavation depth increases gradually with the increase of cohesion,but the change curve of excavation depth and minimum pile length is similar to a straight line,showing that the minimum pile length is 1.8 times of the excavation depth.When the cohesion reaches 12 kPa and the excavation depth is less than or equal to 3 m,the minimum pile length required is 1.8 times of the excavation depth.The second project draws the conclusion that the internal friction angle remains unchanged in the case of PVC sheet pile cantilever bracing structure with water clay foundation pit excavation,and the maximum excavation depth increases with the increasing of cohesion parameter.and the minimum pile length required for the same excavation depth decreases gradually;when the internal friction angle is 20° and 25°,the maximum excavation depth increases gradually.With the increase of cohesion,the maximum excavation depth increases by 0.5m,and the maximum excavation depth increases by 0.4m and 0.5m when the internal friction angle is 30°and 35°.The conclusion of scheme 3 and scheme 4 is similar to the above conclusion,thus verifying the reliability and correctness of the above analysis conclusion.