Site-based Experimental Study On Characteristic Of Pipe-soil Interaction Of4m Diameter Jacking Pipe In Soft Soil

With the progress of equipment technology, the jacking pipe isgetting more larger in diameter, therefore the mechanical characteristics ofpipe-soil interaction of jacking pipe with large diameter in jacking progressmust different from the former jacking pipe with smaller diameter.Currently there are no studies on the field test of4m diameter jacking pipe.Although the mechanical characteristics of4m diameter jacking pipehave been analyzed by some scholars through numerical simulation, theconclusions remain unproved. In this paper, the mechanical characteristicsof4m diameter jacking pipe were analyzed by site-based experimentalcombining the largest diameter pipe jacking project in China. Main tasksand research results are as follows:1. Mechanical characteristics of pipe-soil interaction were analyzed.Variation of the pipeline force, pipe-soil contact pressure, soil and porewater pressure in jacking process were studied. And the influence onpipe-soil contact pressure which caused by grouting pressure was analyzedby using2D numerical simulation finite element method.2. Mechanical characteristics of pipe jacking were analyzed based onfield test. Results showed that the lateral force of pipe is stable, not big,mainly showed compressive stress, and its changing controlled by pipelineaxial deviation and grouting. The pipe is basically in eccentriccompression state under grouting, correction and other complex conditions.The distribution of pipe-soil contact pressure is relatively uniform and thecontact pressure of tip pipe is less than the pressures of both sides of pipe,while the pressure of bottom pipe is the biggest one under the grouting pressure.3. The modes of the distribution of pipe-soil contact pressure and thesize effect of the pipe in different diameter were discussed and analyzedcombined with existing research literature. Conclusions showed that theresults of active soil pressure using the calculate method mentioned in thespecification of pipe jacking is underestimated and the soil reaction forcewithin the range of120°under pipe calculated using Klein theory isoverestimated can both cause design value of internal force too large. Thefactor resulting in the biggest difference between pipe of large and smalldiameter is the size of pipeline in addition to the different soil conditions.4. Variation of soil and pore water pressure of the soil around the pipewere analyzed based on field test results. Studies show that variation ofsoil and pore water pressure of the soil around the pipe with the closingpipe jacking machine head can directly reflect of the disturbance degree ofthe surrounding soil, and the difference in size between machine head andpipe will cause the dramatic changes of soil and pore water pressure. Thedisturbance to surrounding soil caused by slurry balance pipe jacking ismore lessen than the earth pressure balance pipe jacking.This paper made analysis of mechanical characteristics of pipe-soilinteraction of4m jacking pipe in diameter. The results of the study mayprovide a new reference on the pipeline design with large diameter, andwill play an important role in the research on the similar pipe jackingengineering.