Abstract
Under the modern and complicated urban environment, clarifying the interaction mechanism and mutual influence mechanism between the urban tunnel and the surrounding environment is of considerable significance to the construction and operation of the tunnel. To understand and grasp the excavation-induced disturbance range and mechanism of adjacent pipeline jacking group on surrounding soils, this paper carries out relevant researches. Based on a case history of a three-hole parallel adjacent jacking pipeline in shallow overburden, a field test and assessment are performed. By setting monitoring points around the monitoring section, the earth pressure and water pressure under different buried depths and different spacing are monitored. For further discussion, the general law of soil disturbance around single-hole, double-hole, and three-hole jacking is investigated, the calculation method of lateral disturbance range and overlapping area range of pipe jacking group is deduced, and the degree of soil disturbance is evaluated as well. The results show that there will be different degrees of disturbance superposition in parallel multihole jacking due to the influence of the spacing, and the disturbance intensity is greatly affected by the parallel distance and buried depth.
Highlights
Pipe jacking technology is an underground pipeline construction method developed after shield tunnel
It can be seen that, in the double-hole disturbance overlap area, the soil disturbance caused by the second hole is larger than that caused by the first hole, but the disturbance intensity is smaller. is is because the soil structure is more loose when the second hole excavates, and the disturbance caused by the loading and unloading of the soil during jacking is less obvious than that of the original soil before
Combining theory analysis with field test, the effect of soil disturbance in the vertical direction of pipe jacking group and its interaction are mainly discussed in this paper
Summary
Pipe jacking technology is an underground pipeline construction method developed after shield tunnel. It is more significant that the cylindrical hole expansion theory under the isotropic initial stress state can simulate the horizontal excavation construction process of urban underground pipeline and tunnel engineering, analyze the soil disturbance caused by horizontal excavation, and determine the maximum grouting pressure in the hole, which provides a practicable way for the research in this paper. Mohr–Coulomb criterion, by substituting the yield condition (6) into the stress field equation (4), the expansion pressure of the cylindrical hole at the beginning of yielding can be obtained, and it is the radial stress at the radius of the plastic zone: py σ r |r rp. Where h is the vertical distance between the center of pipe segment and ground surface, φ is the internal friction angle of soil, and R′ is the radius of the shell shear disturbance zone, which can be determined by formula (12). If the third hole is jacked in the middle of the previous two holes, it will be further overlapped in the previous two-hole overlapped area, as shown in Figures 4(c) and 4(d). e lateral disturbance zone of the third hole jacking and the lateral overlapping area range are the same as formulas (14) and (17)
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