An Experimental Research On Mold Bag Grouting Pile And Its Applications In Sotf Soil Subgrade

Conventional sleeve-valve-pipe grouting and high-pressure-rotary-jet grouting arecommon treatments for soft roadbed diseases. However, conventional sleeve-valve-pipegrouting often leads to uncontrollable grouting areas and discontinuous piles, whilehigh-pressure-rotary-jet grouting, often leads to excessive soil-compacting effect and slurrywastage. Now a solution to these consequences is proposed by the engineers: the mold baggrouting technology with carefully set mold bags and plastic drain boards.However, there are, so far, few applications of bag grouting technology, and raresystematic researches on its piling mechanism, soil compaction effects, and calculationmethods for designs. In view of the prospects of bag grouting technology, with itsapplicability and merits in the treatments for diseased soft soil subgrade, any further studiesof the technology in engineering and social significance are valuable.On an analysis of the status quo of mold bag grouting technology research, twocomparative experiments are carried out, in the Pilot Project for Dawang InterchangeExit-Ramp A of Erenhot-Guangzhou Super Highway, with mold bag grouting technologyagainst conventional sleeve-valve-pipe grouting technology on the one hand, and in theReinforcement Project of Lianyungang Section of Linhai Top-Graded Highway, with moldbag grouting technology against high-pressure-rotary-jet grouting technology on the other. Aresearch is carried out, combined with theoretical analyses and experiments, on theconstruction parameters, the soil compaction effects, and the calculation methods for designsof mold bag grouting technology. Two other engineering projects, the Shan-Mei(Swatow-Meizhou) Highway Project and the Jiangmen-Xinhui Transit Highway Project, arealso analyzed to give support to the conclusions of the research, with a comprehensiveevaluation of the applicability of mold bag grouting technology in the treatment for diseasedsoft soil subgrade.The fulfillment of the whole research includes the following: Contrast experiments of piling at spot with mold bag grouting against conventionalsleeve-valve-pipe grouting: by observing the in-construction grouting pressure, pore waterpressure, and lateral displacement of surrounding soil, and by testing the post-constructioncore pulling and pile head excavation, both in-construction and post-constructioncomparisons are made between the two construction methods in the aspects of degree, scope,impact of disturbance to the foundation soil, and respective consolidating effects.Contrast experiments of piling at spot with mold bag grouting againsthigh-pressure-rotary-jet grouting: by observing the in-construction grouting pressure, porewater pressure, and lateral displacement of surrounding soil, both in-construction andpost-construction comparisons are made between the two construction methods in the aspectsof degree, scope, impact of disturbance to the foundation soil, and respective consolidatingeffects.Referring to an analysis of piling mechanism of mold bag grouting piles, the calculationmethod for the design of cement mixing pile, the current relevant national specifications, andthe characteristics of mold bag grouting piles, proposed are the calculation methods for thesettlement of single mold bag grouting pile, for the vertical bearing capacity of single pile, forthe stability of subgrade strengthened with mold bag grouting piles, and for the settlement ofcomposite foundation of mold bag grouting piles.Referring to the applications of mold bag grouting piles in the High Speed K32+490Channel Bridge Section Reinforcement Project for Shan-Mei (Swatow-Meizhou) Highway,and in the Jiangmen-Xinhui Transit Highway K2+932Bridge Section Reinforcement Projectfor Provincial Road S364, analyzed are the engineering effects of the mold bag grouting pileson the reinforcement of soft soil subgrade.The results of the research show that, the soil compaction effect of mold bag groutingpiles distributes well between that of conventional sleeve-valve-pipe grouting piles and thatof high-pressure-rotary-jet grouting piles, but with quicker dissipation of excess pore pressurecaused by grouting. Engineering applications report that mold bag grouting piles performquite well in the reinforcement of the existing soft soil subgrade.The author hopes that the results of this research can provide valuable reference for thepopularization and application of mold bag grouting piles in future engineering projects.