砂土地基中微型沟槽隔振效果试验研究

Experimental observation and investigation of the effect of the miniature trench vibration isolation in the sand-soil ground

为了研究微型隔振沟槽的浅层隔振效果,通过进行砂土地基表层瑞利波的现场隔振测试,绘制了相对加速度振幅衰减的二维等值线图,分析了微型隔振沟槽的几何尺寸和位置等因素对隔振效果的影响。结果表明：微型隔振沟槽减隔振措施能有效地阻碍瑞利波在砂土地基表层的传播,一部分瑞利波遇到沟槽发生反射被阻隔在沟槽前方,另一部分通过沟槽两侧绕射及经过沟槽透射至沟槽后方;微型隔振沟槽深度的变化对隔振效果影响较大;而沟槽宽度及长度的变化对隔振效果影响较小;微型隔振沟槽位置的变化对隔振效果影响明显。因此设置微型沟槽对阻隔表面瑞利波是可行的。

This paper is aimed at investigating the vibration isolation effect of the miniature trench in the shallow layer of the sandsoil foundation so as to trace the vibration isolation effect of Rayleigh waves on the surface of such ground. At the same time,it has also analyzed the impact of some factors on the isolation effects,such as the geometrical size and the exact position of the miniature trenches by means of a vibration exciter to stimulate the vibrations in specified frequencies and waveforms. And, to achieve the aforementioned purposes,the paper has arranged the testing points every 10 cm to collect the data of the each point acceleration when the Rayleigh waves pass by the testing spots with the accelerometers armed with the testing instrument. In addition,the maximum value of acquired acceleration should be taken as a reference information by taking a fixed point next to the instrument as a reference point. Furthermore,it is also necessary to take the collected acceleration magnitude and the relative amplitudes as the evaluation standards so as to reduce the likely testing errors. The relative acceleration amplitude can be indicated by the ratio of the maximum acceleration of each testing point to the reference acceleration. Then,we have prepared a two-dimensional contour map of the attenuation of the relative acceleration amplitude. The results show that the miniature trenches can effectively prevent the propagation of the Rayleigh waves on the surface of the sand ground. And,then,some of the Rayleigh waves can be reflected back to when they encounter the trench,but some others can be transmitted with the still others may be diffracted through the two sides of the trenches. Of course,the change of the trench depth may have great influence on the vibration isolation,and,in turn,becoming a significant factor influencing the isolation. Needless to say,it should be set to an appropriate depth,though it should never be too deep or too shallow. On the contrary,the trench width and length of the change merely have little effect on the isolation. Therefore,it would be possible for the miniature trench to be applied for the structure protection in the actual projects. At the same time,the position of such miniature trench can also have a certain effect on the isolation,which should be taken as a key factor influencing the isolation,too.Therefore,the miniature trench can offer an obvious effect,which is feasible to set the miniature trenches as the barriers to Rayleigh waves on the surface of the ground.