三轴试验是土力学领域控制试样固结条件和加载剪切排水条件测试土的强度、变形特性参数的常用试验，也是研究土的强度及本构关系的重要手段。针对国产三轴试验中分别通过压力室体积变化和密封轴向传力杆量测试样应变和轴向荷载的不足，研制了试样的双室压力室，3组独立的伺服步进电机驱动液压缸活塞的液压体变控制器，开发了能够控制不同加载方式、加载或变形速率的自动控制系统和计算控制程序及操作界面。双室压力室的内外腔各自由一组伺服步进电机驱动液压缸活塞的液压体变控制器施加与固结围压相同的液压；试样上端部轴向传力轴固定于压力室顶部，且连接荷载传感器量测试样承受的轴向荷载，试样下端部承受竖向加载轴作用，且与压力室底座密封，竖向加载轴的荷载由一组独立的伺服步进电机驱动液压缸活塞的液压体变控制器控制竖向加载轴下端连接的液压缸加载。该仪器能够自动量测轴向荷载、轴向变形、试样外体变、试验孔隙水压力、压力室内外腔压力。试验验证表明，该仪器系统性能稳定，提高了量测精度，具有构造简单、操作简便、自动化程度高、生产成本低等特点。

Triaxial test is an important mechanical test in geotechnical testing and also in study of strength and constitutive relation. Soil test procedures put triaxial tests as the major experimental projects at home and abroad. Triaxial research and development of triaxial tests are carried out simultaneously. In light of the deficiencies of the existing triaxial apparatus a new triaxial apparatus controlled by hydraulic servo is introduced. The apparatus has a double pressure chamber, surrounded pressures inside and outside the chamber and axial loads is imposed by the hydraulic controller using servo stepper motor drives ball screw pushes the piston to produce hydraulic pressure. Volume deformation measurement is using a stepper motor servo ball screw piston movement displacement to calculate. Data acquisition is controlled by computer. Experimental results show that the deformation of the instrument and volume deformation is measured accurately; instrument system performance is stable. The new triaxial apparatus has the characteristics of a simple structure, easy to operate, the true state of stress, high degree of automation, low production costs, etc. It played a relevant role in promoting the popularity and development of triaxial tests.