| The high-pressure jet-grouting pile grouting method is also called the jet-grouting method.Because of its good reinforcement effect,controllable diameter,strong adaptability to the stratum environment,convenient construction,and low noise,it is widely used in building foundation reinforcement and road support.Wide,tunnel lining,side slope and foundation pit protection,waterproof and water-stopping projects.This paper relies on the newly built Zhongwei-Lanzhou railway connecting to the wide section of the existing Zhongchuan intercity railway subgrade,and the high-pressure jet grouting pile composite foundation construction is carried out.First,the pile forming mechanism of high-pressure jet grouting piles is explained.Based on this,the pile-forming process parameter test and single pile construction soil squeezing test are carried out,and two models of single pile construction and group pile construction are established using finite element software for analysis Finally,combined with the on-site level gauge monitoring data,the impact of the high-pressure jet grouting pile construction on the existing line was summarized,and relevant suggestions were put forward.Through the research of this article,the main conclusions are as follows:(1)The high pressure jet grouting pile will produce soil squeezing effect during construction,which will cause the surrounding soil to move.In the horizontal direction,the closer to the pile core,the greater the displacement of the soil;in the vertical direction,the displacement of the soil continues to increase as the depth decreases.Twenty-four hours after the completion of the initial pile survey,the reclination of the inclinometer tube that is farther away is larger,and the retraction of the soil in the remaining holes is not obvious.(2)According to the calculation and simulation results,during the construction of a single pile of high-pressure jet grouting piles,the displacement of the soil increases continuously with the increase of the grouting pressure,and the displacement of the soil layer will change suddenly.When the grouting pressure is 27 MPa,the maximum influence range of the squeezing effect is 6.83 m.(3)The multi-pile construction of high-pressure jet grouting piles will cause a certain vertical and horizontal displacement of the existing subgrade.When the construction is close to the analysis section,the horizontal and vertical displacement of the existing subgrade on the section will increase significantly,and the Existing foundation produces a squeezing effect.There is a cumulative effect during multi-pile construction.As the grouting pressure increases,the displacement of the soil in all directions also increases.(4)Comparing the data during construction without stress relief holes,after construction with stress relief holes,it can effectively reduce the displacement and deformation of the existing roadbed and foundation,reduce the uneven deformation and settlement of the existing lines,and protect driving safety.At the same time,the construction control index is proposed,that is,when the horizontal displacement of the existing line is greater than 2mm/d,or the vertical displacement is greater than 8mm/d,the construction must be stopped.(5)The monitoring results of the monitoring data show that the construction of high-pressure jet grouting piles will cause differential settlement of the existing line,and the vertical displacement of the existing roadbed during the construction of both sides appears as uplift deformation first,and then settlement deformation.It is recommended to maintain a safe construction distance and set up protective measures,and at the same time strictly control construction parameters and construction intensity,strengthen deformation monitoring at special locations such as culverts and abutments to ensure the safety of existing lines. |
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