巷道/隧道围岩的开挖卸荷效应，直接关系到围岩稳定、支护设计和施工工艺的选择。利用自主研发的开挖卸荷试验系统，对水泥砂浆制作的厚壁圆筒小型围岩试件进行了快、慢速卸荷试验研究，获得小型围岩试件在开挖卸荷过程中的变形规律与破坏形态。试验结果表明:① 快、慢速卸荷的径向应变及切向应变与时间的关系曲线表现出明显的3个特征阶段:试件压密阶段、快速变形阶段、卸荷后缓慢变形阶段。② 同一横断面处，内侧的切向应变对卸荷作用反应更快、更显著，变形量更大。径向内侧产生的变形总量均大于外侧，而轴向内侧产生的变形总量小于外侧。③ 无论快速或慢速卸荷，同一测点处，切向应变最大，占据重要地位。径向变形集中在卸荷阶段产生，轴向变形集中在卸荷后维持阶段产生。④ 卸荷阶段，随着压差增大，慢速卸荷的切向、轴向应变呈加速发展趋势，内、外侧径向应变差值约为200×10^-6。快速卸荷的切向、轴向应变呈收敛发展趋势，内、外侧径向应变基本相同。维持阶段，快、慢速卸荷切向、轴向内外侧偏差持续增大。快速卸荷时内、外侧径向应变在维持阶段才开始区别开来，且差值越来越大。⑤ 试件压缩高度变低，且外侧出现环状贯通面并伴随劈裂破坏，在内壁出现片状剪切破坏区;横断面出现两个类似于圆环破坏带的破坏区。

The excavation unloading effect of roadway / tunnel surrounding rock is directly related to the stability of sur- rounding rock,the design of support and the selection of construction technology. Fast and slow unloading experiments were carried out to study the excavation unloading effect of small surrounding rock specimens made from cement mortar by using the independently developed experimental system of excavation and unloading. Deformation laws and failure patterns of the excavation unloading process were obtained. The test results show that:① The relation curves of radial strain and tangential strain in fast and slow unloading and time show three characteristic stages:specimen compaction stage,rapid deformation stage,and slow deformation stage. ② In the same cross section,the tangential strain of the in- ner side reacts faster and more significantly to the unloading action,and greater deformation is produced. The total de- formation produced by the inner side radial is greater than that on the outer side,while the total deformation produced by the inner side axis is less than that on the outer side. ③ No matter fast or slow unloading,the tangential strain at the same point is the most important and occupies an eminent position. The radial deformation is concentrated at unloading phase,and the axial deformation is concentrated in the maintenance phase after unloading. ④ In the unloading phase, with the increase in pressure difference,the tangential and axial strain of slow unloading show an accelerated develop- ment trend,and the radial strain difference value of inner and outer is about 200. The tangential and axial strains of quick unloading show a tendency of convergence,and the radial strains of inner and outer are basically the same. Dur- ing the maintenance phase,the tangential and axial inner and outer deviations of the two unloading methods continue to increase. In the fast unloading phase,the radial strain on the inside and out lateral starts to differentiate and the differ- ence becomes larger and larger. ⑤ The specimen is compressed and becomes shorter,and the annular penetrating sur- face appears on the outside and is accompanied by splitting failure,and the inner wall shows a slice-like shear failure zone. There are two damage zones in the cross section parallel to the ring damage zone.