| PHC pipe pile (pre-stressed high-strength concrete pipe running) the high strength prestressed concrete pipe pile, it is in recent years in our country began to promote a new pile type. Because this type of pile in foundation reinforcement, construction period, construction cost, and environmental aspects such as compared with the traditional foundation treatment method has obvious advantages, so its application in engineering more and more common. Using post grouting technique to improve the bearing capacity of single pile and pile reinforcing engineering case also happen from time to tome, but pile bottom of PHC pipe pile and pile extension after grouting between stress and strain change rule research rarely, related design specifications and acceptance standard of construction has not yet been introduced and the promoting of the innovation process. In this paper, on the basis of predecessors’pile bottom grouting test, through the engineering experiment and FLAC3D numerical simulation analysis of PHC pipe pile end and pile extension between stress and strain change rule of soil grouting pile are studied, the main work of this article have the following content:First, this paper introduces the advantages of PHC pipe pile, defects, suitable for the formation and development of PHC pipe pile characteristics and research progress of PHC pipe pile grouting technique at home and abroad, combined with the above content, the author puts forward the main work of this article. Then, combining previous pile bottom grouting test, the author by hefei in anhui province economic development zone A, B two adjacent project, A project of PHC pipe pile grouting treatment, and B project in the construction unit, supervision unit, design unit, supported by innovative select three PHC pipe pile grouting technology in pile by pile and pile bottom grouting) (hereinafter referred to as grouting PHC pipe pile, and then through the static load test and low strain test, analysis of two project test pile load-settlement curve, at the same time, through the finite difference software FLAC3D simulation end of PHC pipe pile and pile extension between stress and strain change rule of soil grouting pile, finally get the following results:1, PHC pipe pile pile splicing process usually adopt welding method, due to the limitation of grouting construction technology and the little pile of grouting technology was studied, based on the improved "bullet" innovation process in the PHC pipe pile pipe section grouting grouting pile extension of success. "Bullet" grouting pipe section of the grouting construction technology can effectively solve the PHC pipe pile and pile extension of easy corrosion engineering quality common fault.2, B engineering pile, grouting PHC pipe pile, pile after pile and pile bottom grouting PHC pipe pile) of the axial force of pile is similar to the changes of PHC pipe pile grouting, are distributed "inverted triangle", along the depth direction gradually decay, axial stress of pile top is greater than the lower. After grouting the attenuation of the axial force of PHC pipe piles for the slope is greater than the PHC pipe pile axial force attenuation velocity of slope.3, Comparison and analysis of A and B two project PHC pipe pile Q-s curve are slowly, from small strain test analysis shows that when the settlement is greater than 40 mm, pile failed to meet the limit state, description of the bearing capacity of the pile itself still has A certain, so the pile end eventually instability is caused by the destruction of the pile endpoint soil, so it can be seen through by pile and pile bottom grouting on the bearing capacity of pile foundation is feasible.4, In the similar geological conditions, selection of pile foundation case, by contrast, not PHC pipe pile PHC pipe pile and grouting of the Q-S relationship contrast curve shows that through the pile by pile and the ultimate bearing capacity of pile bottom grouting pile foundation, A project without grouting three ultimate bearing capacity of PHC pipe pile average of 44266.7 kN, and B projects limited bearing capacity of PHC pipe pile after grouting the mean value of 5533.3 kN. After grouting the bearing capacity of PHC pipe piles by about 25.0%.5,Through A, B two project PHC pipe pile static load experiment ultimate bearing capacity compared to the "code for building pile foundation technology (JGJ106-2014) the experience formula of PHC pipe piles under the similar geological conditions proposed new limit bearing capacity formula:(1) not grouting PHC pipe pile: Qu= 2Quk= 2a1[u∑qsikli+qpk(Aj+λAp1)]α1= 0.95～1.14(2) after pile by pile and pile bottom grouting PHC pipe pile: Qu= 2Quk= 2α2[uX qsikl,+gjAj+A/pl)] a2= 1.29-1.38In June, according to the test of various material parameters to establish the finite element model analysis shows that when the pile top pressure respectively is 1000 kn and 2000 kn,3000 kn and 4000 kn in pile by pile after grouting pile extension of PHC pipe piles in axial force is higher than without grouting of PHC pipe piles respectively 9%,12.1%,14.6%,12.1%, coefficient of axial force increase with the pile top pressure increases, the approximate linear relationship. Using origin8.5 large numerical analysis software to carry on the fitting, fitting equation fory= 1.0705+2.35* 10-5 x (1000 kn x or less 4000 kn) or less, R2= 0.9611. 7, The computed model under the same load, settlement and pile body stress agreed with experimental results. Experiments under limit load and grouting amount of PHC pipe pile and the settlement of PHC pipe pile is 42.64 mm and 40.87 mm, and the finite element model of grouting PHC pipe pile, and models of PHC pipe pile settlement is 47.45 mm and 41.24 mm, and the load-settlement curve can be seen in the measured values are in good agreement with the model calculation values; At the same time test and PHC pipe pile grouting PHC pipe pile in model of the pile stress conversion of axial anastomosis is better also, suggested that PHC pipe pile with FLAC3D numerical calculation result is reasonable and accurate. |
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