Research and application of relative density test method for large coarse-grained soil
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摘要: 结合拉哇特高面板坝堆石料的设计填筑级配，采用数值试验和现场试验手段，研究了影响大型密度桶试验精度的主要因素，提出了堆石料的孔隙率和相对密度双控填筑指标，并结合碾压试验成果验证其适用性。结果表明：①对于难以充分拌匀的大粒径粗粒土现场密度桶试验，采用人工分层装样方式，可有效减小试验结果的离散性。②密度桶尺寸的选择对试验结果影响较大，过大的尺寸带来较高的试验成本，甚至难以实施，过小的尺寸会带来明显的容器边界尺寸效应。综合现场实际情况，密度桶试验尺寸满足最小径径比和高径比分别在4.0，2.0左右时，试验结果的尺寸效应相对较小。③随着最大粒径的增加，密度桶试验的极值干密度均呈现增加的趋势，但当最大粒径达到300~400 mm以后，极值干密度基本稳定，试验结果可以作为压实设计和填筑质量控制的依据。④试验得到拉哇角闪片岩堆石料的双控填筑指标为：孔隙率不高于19%时相对密度不低于0.73。采用32 t振动碾振动碾压12遍，即可满足要求。⑤采用水平分层碾压的大粒径粗粒土，适当提高压实层厚度与最大粒径的比值，可以取得更佳的压实效率。堆石料取松铺层厚1.0 m左右、最大粒径400~600 mm，是一种较优的压实方案。研究成果可直接应用于大粒径粗粒土的填筑设计和评价，具有较强的应用价值。Abstract: Based on the design filling gradation of rockfill materials for Lawa super-high face dam, the main factors affecting the test accuracy of large density barrel are studied by means of numerical and field tests. The double-control index of rockfill porosity and relative density is proposed, and its applicability is verified by the results of rolling tests. The results show that: (1) For the field density barrel tests on the coarse-grained soil with a large particle size, which is difficult to be fully mixed, the method of artificial layering can effectively reduce the discreteness of the test results. (2) The selection of container size has a great influence on the test results, and too large size will bring higher test cost, even difficult to implement, while too small size will bring obvious container boundary size effect. Considering the actual situation in the field, the size effect of the test results is relatively small when the density barrel test size meets the minimum 'diameter to diameter ratio' and the 'height to diameter ratio' is about 4.0 and 2.0, respectively. (3) With the increase of the maximum particle size, the extreme dry density of density barrel tests shows an increasing trend. However, when the maximum particle size reaches 400 mm, the extreme dry density is basically stable. The test results can be used as the basis for compaction design and filling quality control. (4) The porosity is not higher than 19% and the relative density is not less than 0.75. The requirements can be met by using 32T vibration rolling 12 times. (5) For the soil with a large particle size with horizontal layered compaction, the ratio of the thickness of compaction layer to the maximum particle size can be appropriately increased, which can achieve better compaction efficiency. It is an optimal compaction scheme for rockfill materials to take a loose paving layer with a thickness of about 1.0 m and a maximum particle size of 400~600 mm. The research results can be directly applied to the compaction design and evaluation of coarse-grained soil with large particle size, which has a great application value.
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Keywords:
- CFRD /
- coarse grained soil /
- filling standard /
- porosity rate /
- relative density /
- test method /
- dry density size effect
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图 3 休止角堆积数值模拟流程图
Figure 3. Flow chart of numerical simulation of angle of repose stacking
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图 4 休止角的室内物理试验及数值试验结果
Figure 4. Results of experimental and numerical tests angle of repose
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图 10 先放大颗粒后放细颗粒装样图
Figure 10. Sample with large particles first and then fine particles
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图 11 不同装样方式及高径比条件下孔隙率频率分布
Figure 11. Distribution of porosity frequency under different packing modes and H0/dmax conditions
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图 12 不同装样方式及高径比条件下孔隙率正态分布
Figure 12. Normal distribution of porosity under different packing modes and H0/dmax conditions
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图 16 堆石料大型相对密度试验级配
Figure 16. Grading of large-scale relative density tests on rockfill
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图 18 平均级配（不同dmax）堆石料的相对密度试验结果
Figure 18. Results of field relative density tests of average graded rockfill (different dmax)
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图 19 堆石料的现场密度桶试验示意图
Figure 19. Schematic diagram of field density barrel tests on rockfill
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图 20 堆石料现场相对密度试验三因素图
Figure 20. Three-factor diagram of relative density tests on rockfill
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图 21 堆石坝体最大粒径与摊铺压实层厚示意图
Figure 21. Schematic diagram of maximum particle size of rockfill and thickness of compacted layer
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图 22 最大干密度试样切片及分层孔隙率
Figure 22. Schematic diagram of sample slice and stratified porosity
表 1 数值试验颗粒细观参数
Table 1 Micro-parameters of numerical tests
颗粒密度/(g·cm-3) 摩擦系数 抗转动系数 弹性模量/GPa 刚度比 2.975 0.4 0.4 1.6 2.0 
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表 2 不同装样方式试验方案
Table 2 Test schemes for different packing methods
密度桶尺寸 混合装样 分层装样 “先大后小”装样 合计/组 径径比=4.0 高径比=2.0 40 40 40 120 高径比=1.2 40 — — 40
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表 3 填料施工摊铺碾压参数和压实效率
Table 3 Parameters and results of construction compaction
工程名 类型 最大粒径/mm H0/d0max 碾压遍数 孔隙率/% 两河口 堆石 800 1.0 8 ≤21 句容抽蓄 堆石 700 1.1 8 ≤19 阿尔塔什 堆石 600 1.5 8 ≤18 砂砾 400 2.0 10 ≤15
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