Experimental Study On Bearing Mechanism And Combinatorial Optimization Of JPP Pile

Jet grouting soil-cement-pile strengthened piles(JPP) is a kind of composite piles is suitable for the new type of composite pile in soft soil, can effectively improve the vertical bearing capacity of pile, and application of comparable size were obtained. Jet grouting soil-cement-pile strengthened piles(JPP) is the high pressure jet grouting pile and prestressed concrete core pile by combination of a new type of composite pile, a variety of combinations in practical engineering, but what the optimal combination form is always a difficulty in the designer. To study under the different combinations of JPP pile load-bearing characteristics, in this article, through the indoor model test, numerical analysis and theoretical derivation method of combinatorial optimization of pile bearing mechanism was studied, and get the following conclusion:(1)Use of the existing equipment independent research and development the model test of pile foundation loading system, loading system, measurement system for the upgrading, meet the requirements of the model test of pile foundation.(2)Conducted four different combinations JPP pile vertical load testresearch, analysis of the vertical bearing capacity of the system, mastered the four kinds of vertical load transfer law of composite piles is obtained form the optimal combination of the pile. The results show that in the pile of 4 kinds of combinations, piecewise combination Ⅱ can provide maximum bearing capacity of pile, visible in the different combination forms of the soil and core has a great influence on bearing capacity of pile. Cement-soil after segmentation, similar to the bottle gourd of surface, increases the pile of pile and soil roughness, and each section of the cement-soil end department can provide a certain amount of end resistance and bearing capacity increase significantly. Combination section position has also has great effect on the bearing capacity, the lower the soil core and composite pile side friction significantly increased, the composite pile bearing capacity show the score of the characteristics of big section bearing capacity of combined Ⅰ visible combination should be designed at the bottom of the pile.(3) Conducted four different combinations, experimental study on horizontal bearing capacity of JPP pile of horizontal load-bearing characteristics analyzed, mastered the four kinds of composite pile horizontal load transfer law. The results show that in the pile of 4 kinds of combinations, piecewise combination Ⅱ JPP pile provide maximum bearing capacity. In combination with piecewise combination I close, the combination of JPP pile horizontal bearing capacity of the lowest, that segment combination presents the characteristics of the whole under horizontal load ability is stronger. This is because the piecewise combination is a combination of high bending strength of core pile and cement-soil section pile reinforcement soil properties, forming a similar type hoist diameter pile horizontal load, enhance the level of resistance to carrying capacity of wholeness, therefore ascending in the horizontal bearing capacity is bigger, significantly increase the flexural capacity of JPP pile. Through experiment found that the maximum bending moment of JPP pile in distance from the following 2 times the pile diameter, pile head easily occur in the region is relatively weak, so in this range should be cement-soil pile soil reinforcement and increase core flexural capacity of the pile in this scope.(4) Using ANSYS finite element software main combination factors affecting the pile bearing performance of the numerical analysis, the research results show that different combination forms of greater influence on the pile bearing performance, within the scope of JPP pile body in the same soil layer, segmentation, the more portfolio section location to the pile body, bearing capacity is higher. Visible, in the actual engineering practice, should be in a good soil layer, as much as possible of high pressure jet grouting, segmentation and appropriate jet grouting in the pile body department.(5)The finite element software ANSYS to affect combination of pile bearing performance of the main factors in the numerical analysis, the research results show that different combination forms of JPP pile bearing performance, within the scope of pile body in the same soil layer, segmentation, the more portfolio section location to the pile body, bearing capacity is higher. Visible, in the actual engineering practice, should be in a good soil layer, as much as possible of high pressure jet grouting, segmentation and appropriate jet grouting in the pile body department.