大型原位直剪试验的试样尺寸大，对土体扰动小，是获取岩土体强度参数的有效方法。中国科学院武汉岩土力学研究所在参考室内、现场两用大型直剪仪后，又改进研制了一套大型原位剪切设备。与传统原位直剪设备不同，该设备采用上、下两个刚性剪切盒，可完成尺寸为50 cm×50 cm×41 cm，最大粒径为5 cm的原位土体试样的剪切试验。该直剪设备组装方便，采用高精度传感器可自动采集数据，更适合于复杂的现场试验环境。介绍了该设备的结构组成、工作原理、技术优点。结合实例详细介绍了大型原位直剪试验的试验方法及注意事项。将此大型原位直剪设备应用于向家坝库区两个滑坡现场试验，得到了滑坡滑带、滑体的原位抗剪强度参数，分析了不同试样大型原位直剪试验剪切曲线的特点，进一步论证了该直剪设备的优良工作性能。

With large sample size and slight disturbance of sample’s original structure, a large scale in-situ direct shear test is an effective method for obtaining the strength parameters of material in geotechnical engineering. After investigating a set of direct shear apparatus for field and laboratory tests, a set of large scale in-situ direct shear apparatus is developed by Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. The apparatus is different from the traditional in-situ direct shear apparatus. It has an upper rigid shear box and a lower one, and is competent to conduct in-situ direct tests on soil sample with size of 50 cm×50 cm×41 cm and the largest grain size of 5 cm. It is convenient for assembly and suitable for complex field test environment. It can collect data automatically with a high precision sensor. This paper introduces the configuration, operation principle and technical advantages of the improved apparatus and describes the usages and problems encountered during testing on site in detail. The apparatus is applied to field tests of two landslides on Xiangjiaba reservoir to obtain the in-situ shear strength parameters of soil. Through analysis of shear strength curves for different samples, the apparatus is verified to have excellent performance.