Development of An Acoustic Emission Cone

土的颗粒大小是决定土的液化强度的重要或主要参数之一。人们希望同时拥有关于土壤性质的信息以及CPT数据。研制了一种新型圆锥贯入仪，其顶端安装了声发射(AE)传感器。初步结论如下：1.采用4种不同类型的砂土进行箱形抗剪试验。研究了颗粒尺寸和围压对剪切时声发射特性的影响。声发射总数随平均粒径和围压的增大而增加。在由砂土和粘土交替组成的模型地基上进行了声发射触探试验。声发射在砂层中发育明显，并可识别出夹在粘土层之间的薄砂层。声发射计数率与锥体阻力之间的确切关系目前正在研究中。回顾了过去有关声发射计数率与平均粒度之间关系的文献，并绘制在图表中。在该图中，纵坐标为AE(D_(50))与AE(D_(50)=0.25)之比，横坐标为平均粒度(D_(50))。在此基础上叠加了箱形剪切试验结果。由于声发射数据的分散性，从图解中预测土体液化势的准确性相当困难。在考虑围压影响的同时，还需要进一步的研究。

The grain-size of the soil is one of the important or dominating parameter in determining the liquefaction strength of the soil. There is desire to have simultaneously, the information on the properties of soil along with the CPT data. A new cone penetrameter has been developed which has an acoustic emission (AE) sensor installed at its tip. The tentative conclusions are as follows:1. Box shear tests were performed by using 4 different types of sand. The influence of grain-size and the confining pressure on the characteristics of AE when sheared has been investigated. The total AE count increases with the increase in average mean grain-size and the confining pressure.2. AE cone penetration testing has been carried out on the model ground made-up of alternating layers of sand and clay. The development of the acoustic emission is obvious in the sand layer, moreover, a thin sand layer sandwiched between clay layers could also be recognized. The exact relation between AE count rate and cone resistance, at present is under investigation.3. Past literature on the relationship between AE count rate and average grain-size have been reviewed and plotted in the diagram. In this diagram the ordinate is taken as the ratio of AE(D_<50>) and AE(D_<50>=0.25) and the abscissa is taken as average mean grain-size (D_<50>). Results of box shear test have been superimposed on it. The accuracy in predicting the liquefaction potential of soil from the diagram is, rather difficult owing to the scattering of the AE data. Further research is needed while taking into the consideration the effect of the confining pressure.