自钻式原位液化试验仪

efaction resistance of soil. This machine mainly consists of a self-boring drilling system, a liquefaction measuring system, a torque servo system, an inner pressure control system, and a data acquisition control system. The liquefaction measuring system contains a cylindrical rubber membrane and a loading metal board. It also has a displacement sensor and a pore pressure transducer. Its characteristic parameters include: 300mm of measurement zone in length; 10mm of outer diameter (with no pressure applied); 600kPa of inner pressure; up to 5Hz of loading frequency. The pressure in the chamber is provided by a pressure control system on the ground. In addition, the torque servo system is adopted to provide and control the dynamic shearing stress. The main advantage of this device is the little disturbance to soil sample, as well as the automatic control of the lateral pressure and dynamic shearing stress. The device, which is the first in-situ liquefaction tester appeared in our country, is capable to determine liquefaction resistance at different depths in an undisturbed soil, and hence to reflect the effects of stress state and soil structure on the liquefaction resistance accurately. This project provides technical supports for identification and treatment of ground liquefaction in the construction of a large-scale infrastructure and underground exploitation in our country.

本项目旨在研发一种用于在现场测定地基土的抗液化强度参数的自钻式原位液化试验仪。该仪器主要由自钻式钻进系统、液化测定器系统、扭力伺服系统、内压控制系统和控制采集系统等组成。液化测定器系统是由圆筒橡皮膜、加载金属板等组成，测定区的长度为300mm，无压力时外径为10mm，内压600kPa，系统可提供的加载频率最高达5Hz。该设备采用自钻系统，液化测定器系统上配有位移传感器和孔压传感器，腔体内压力由地面压力控制系统提供，动剪应力由扭力伺服系统提供和控制；具有对土体扰动小，侧向压力和动剪应力可以实现自动控制的功能。该仪器研制可以填补我国土体原位液化测定仪的空白，可用于在原位应力条件下测定不同深度处不受扰动土体的抗液化强度，能够更加真实地反映土体原位应力和结构性对其液化强度的影响，为我国大型基础设施建设和地下空间开发利用中地基液化的判断和设计与维护提供重要的技术支持。

本项目通过仪器的加工研制以及室内和现场试验，对自钻式原位液化试验仪具备的功能和性能指标进行了比较系统的测定和验证。测定结果表明：所研制仪器的功能符合设计要求，仪器设备的主要性能指标也满足要求。土层液化测定器在判断土层是否发生液化的同时还能够测定土体内的孔隙水压力和土体发生的体积变化；扭力施加装置和伺服系统能够将预先设定好加载频率和波形的动荷载传递到液化测定器的顶部，通过液化测定器传递到土体中，并在测试的过程中保持设定的加载频率和波形稳定可控；内压力控制系统能够通过控制器分别控制液化测定器的上、中、下三个压力腔体压力的大小，并能够根据试验的需要在试验过程中调整压力的大；信号控制、转换及计算机控制系统能够保证在试验过程中实时监测到液化发展过程中相应数据的变化情况。本设备在埋深为25m以内的土层内进行土层液化特性测定时，可以根据要求施加预定的侧向压力和水平向的动荷载，在测定过程中测定土体的超孔隙水压力和土体的变形，并根据超孔隙水压力和土体的变形的大小来初步判断土层是否发生液化，从而实现土层液化性能初步的判定，为进一步系统研究土体的液化特性提供了一种较好的方法和手段。