STUDY OF MECHANISM AND PREDICTION OF GROUTING UPLIFT IN TUNNEL CONSTRUCTION UNDERCROSSING BUILDINGS

Based on the analysis of settlement recovery characteristics of buildings,grouting uplift mechanism is analyzed in detail,consisting of four phases,i.e.ground fill and compaction,construction of exterior isolation curtain structure,formation of uplift force and building structure uplift.The key techniques of steady uplift of buildings are then summarized.The grouting uplift during tunnel construction undercrossing experimental buildings #104 and #105 is predicted by numerical simulation.The results indicate that the maximum uplift is 2.1-3.7 mm.It is also shown that uplift force and stiffness of exterior isolation curtain will influence the uplift effect significantly;and proper increments of these two factors are favorable to some degree.For comparison,the field test is introduced,showing a repeated process of soil fracturing,filling and fracturing again.Obvious uplift of the buildings begins when grouting pressure reaches 0.7-1.0 MPa,and the single maximum uplift is 2.2-3.1 mm,which is nearly close to the simulation result.All conclusions are helpful for improving the scientific understanding of safety control of urban tunnel construction and providing references for similar projects.