Research On The Experiment And The Cavity Forming Mechanism Of The Expanded End Of The Airbag Reaming Anchor

In order to obtain a larger anchoring force of the soil anchor, the use of expanded end anchor is one of the common methods. The method of forming the enlarged end, that have mechanical reaming, explosion reaming, hydraulic reaming, airbags reaming,etc.The method of airbag reaming first is use some instruments in the soil into the hole,and then the airbag cover drill holes placed in the set position, inflatable, balloon inflated extruded surrounding soil,such that soilcompression, a certain diameter empty cavity, pouringconcrete to form an enlarged anchor.In order to obtain the relationship between the inflation pressure and the diameter of the cavity, carried out airbag inflator reaming experiment. The main tool needed for the experiment cylindrical airbag (with a bicycle inner tube production), has opened a hole in the pipe inflated, blocking the hole plugs and so on. Carried out in the soil inflatable reaming experiments, at different pressures to inflate the airbag, forming a cavity having different diameters.Injection method, water in the cavity of a plastic bag, measuring the volume of water, and seek the cavity diameter. Inflation pressure and get the relationship between the diameter of the cavity, function quadratic function type,y=177.69x2-6.3573x+0.9948Testpoints are obtained on these condary function of the image. The initial phase of the airbag inflator with pressure increases slowly open, there by squeezing the soil, when the inflation pressure reached-aftervalue,inflation pressure over the balloon itself bearing capacity, balloon destruction.By numerical simulation FLAC3D,establish inflated numerical model to simulate the deformation of the soil under the effect of inflation pressure, the simulation results for the relationship between inflation pressure and reaming diameter,experimental and simulation results coincide. In the simulation, the constitutive relation of soil to take Mohr-Coulomb model, Failure criterion for Mohr-Coulomb guidelines, Calculated reaches a certain value, and then increase the pressure, to expand the cavity deformed to a certain value, the simulation result is no longer converge. According to the formula of Rankine earth pressure, to caculate the value of passive earth pressure0.12Mpa, experimentally derived maximum inflation pressure of0.5Mpa, the experimental and calculated values ratio of4.17.Much larger than the experimental values calculated, this phenomenon is due to the experiment being squeezed cavity surrounding soil, the soil itself gradually increase the intensity, the pressure value is increased.In the simulation, within a certain range, the farther away f rom the stress of the cavity with the displacement decreases until the soil is still pressure on the role of stress range is limited.