چكيده به لاتين
Explosive compaction or Blast Densification is a deep soil treatment method that has been practiced for over 70 years. Evaluation of soil behaviour during and after of EC is important because it indicates the effect of EC on the improvement of soil characteristics. Pour water pressure and settlement are important parameters in EC which is used to detect liquefaction and soil compaction, respectively.
In this dissertation, EC performance is assessed for saturated sand with numerical method and field measurements. LS-DYNA software is used for numerical section and EC performance is evaluated for two states of single borehole and square arrangement charges. A field test is conducted on a railway subgrade that consists of four squarely arranged explosive boreholes with simultaneous detonation. An advanced numerical formulation is then used to back-calculate the test and perform. The EC performance is controlled by changing explosive depth, weight, size, and detonation delay. Concerning the results discussed, the numerical evaluation approach exhibits promising advantages compared to other conventional methods. It provides a cost-effective method with reasonable accuracy. According to the results, as the depth of explosive increased the surface heave decreased. Thus, by considering the resulting settlement an optimum depth of explosives should be considered. For a single blast, a depth around 7–8 m can result in an effective EC, which is approximately 2/3 of the soil layer depth. By imposing detonation delay, the resulting settlement improved, both in case of induced heave and post-blast settlement in comparison to the case where the charges detonated simultaneously. Increase in charge weight magnifies the explosion effect, but as the compaction increases, the induced surface heave increases too. Permeability did not affect the induced compression during the blast due to undrained nature of the explosion. But for post-blast settlement, by an increase in permeability value the resulting settlement increases, however, the difference is not so much. The effect of detonation delay in EC regarding its improvements is studied. By applying the delay, more compaction and less surface heaving was observed.
