结构面模型制作过程中,在模型内灌注一定量流动的水泥砂浆,再将结构面试样直接放置在流动的水泥砂浆上,会引起试样的不均匀沉降;然而结构面的直剪试验中要求制作的结构面模型必须水平,否则在进行直剪试验时,将直接导致结构面与仪器所加竖向力不能垂直,即法向应力与剪切应力不垂直,这将导致试验结果与实际情况出现很大误差甚至完全错误。基于此,在岩体结构面的直剪试验中,一种制作结构面模型的防沉降仪被提出,包括:外支架、活动长杆、夹持板、挂钩、蝶形螺母等。在结构面模型的制作过程中,通过使用结构面模型的防沉降仪,将结构面试样夹紧使其固定不动,避免了其发生不均匀沉降和沉降量过大的现象。

In the preparation of structural surface model, cement mortar is poured into the model, and then structural surface specimen is placed directly on the flowing cement mortar, resulting in uneven settlement of the specimen. However, the structural surface model must be horizontal in direct shear test; otherwise the structural surface is not perpendicular to the vertical force of shear apparatus, which means that normal stress is not perpendicular to shear stress, leading to big error or even completely wrong result compared with the actual situation. In view of this, an instrument of preventing structural surface model from settlement in direct shear test of rock mass is proposed. The instrument consists of an outer frame, active pole, clamping plate, hook, wing nuts and so on. In preparing structural surface model, the specimen is clamped tight and fixed to secure it does not move, which avoids the uneven settlement and excessive subsidence.