大石峡高面板坝筑坝砂砾料现场大型相对密度试验

当前，主要采用相对密度来表征筑坝砂砾料的密实程度，并以此来评价大坝的施工碾压质量。受试验设备尺寸和击实功能的限制，室内试验难以反映现场实际筑坝砂砾料粒径大、采用大型碾压机具进行高强度碾压的实际情况，试验确定砂砾料最大干密度值偏低，难以直接用于指导实际工程。针对大石峡高面板坝筑坝砂砾料，在工地现场采用实际筑坝碾压设备和大型相对密度桶，对原级配坝料开展相对密度试验，研究了坝料的压实特性，确定了不同级配（含砾量）坝料的相对密度特性指标。研究表明：比较室内试验成果，现场试验确定砂砾料最大干密度值有较大提高；随着含砾量的增加，砂砾料的最大、最小干密度值先增加、后减小，存在压实密度最高的最优含砾量特征值；强振碾压使得弱胶结砂砾料产生不同程度的颗粒破碎效应，颗粒破碎的程度和土料的原始级配特性相关联。

Field Large-Scale Relative Density Tests of Gravel Soil of Dashixia High Concrete Faced Rock-Fill Dam

The compaction rate of gravel soil is usually characterized by the "relative density", which is used to evaluate the compaction quality of dam construction. Restricted by the size and energy limitation of the laboratory test equipment, the laboratory tests are difficult to reflect the actual situation of high strength compaction of gravel soil by large rolling equipment;and the maximum dry density of the gravel soils obtained in laboratory tests is often much lower than the actual one, so it cannot be directly used in practical engineering. To the sand and gravel materials for the Dashixia high concrete faced rock-fill dam, the field large-scale relative density test of original gravel soil was carried out by using the actual rolling equipment and large relative density bucket on the site, the compaction characteristics of soil was studied, and further the relative density characteristic indexes of soils with different gradation (coarse grain content) were determined. The test results show that the maximum dry density of gravel soil determined by field test is greatly improved compared to a general laboratory test; the minimum and maximum dry densities of gravel soil show a tendency of increasing at first and then decreasing with the increase of the coarse grain content, and there is an optimal coarse grain content value with the highest compaction density of soil; the strong vibration compaction results in different degrees of particle crushing effect on weakly cemented gravel materials, and the degree of particle crushing is related to the original grading characteristics of soil materials.