SHEAR MECHANICAL PROPERTIES OF DREDGED CORAL SANDS FROM SOUTH CHINA SEA, CHINA
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摘要: 珊瑚砂作为一种特殊的生物碎屑沉积物，我国南海广泛分布，其具有多孔、非均质、非连续等工程特性，作为填岛的材料和工程建设的基础，吹填珊瑚砂的力学特性是珊瑚岛礁工程研究的关键科学问题。中国南海降雨量大，吹填珊瑚砂渗透性好，工程荷载高，含水性和高荷载对于吹填珊瑚砂剪切力学特性的影响非常显著。利用自主研制的土石混合体大型剪切力学试验机，采用中国南沙某岛礁吹填珊瑚砂，在级配和组分分析的基础上，研究不同密实度、含水量条件下高轴向荷载珊瑚砂的剪切力学特性，通过试验结果分析得出如下结论：(1)含水量增加导致吹填珊瑚砂抗剪强度减小，呈负相关关系；密实度增加引起抗剪强度增加，呈正相关关系；(2)含水量对吹填珊瑚砂内摩擦角影响显著，呈负相关关系，含水量大于10%，内摩擦角降低较小；密实度90%时，含水量大于5%，黏聚力降低较小；(3)密实度对吹填珊瑚砂的黏聚力影响规律不明显，密实度对内摩擦角影响较显著，当含水量大于5%时，随着密实度的增加内摩擦角显著增大；(4)在高荷载条件下，含水量和密实度对吹填珊瑚砂抗剪力学特性影响较为显著，含水量小、密实度大的吹填珊瑚砂抗剪特性最强，对于岛礁填岛工程设计及场地条件改性具有指导意义。Abstract: Coral sand, as a special bioclastic sediment, is widely distributed in the South China Sea. It has many engineering characteristics such as porous, heterogeneous and discontinuous. As the basis of island filling materials and engineering construction, the mechanical properties of the dredged coral sand are the key scientific issues in the research of coral island and reef engineering. The South China Sea has a large amount of rainfall. The dredged coral sand has good permeability and high engineering bearing capacity. The influence of water content and high load on the shear mechanical properties of the sand is very significant. Based on the analysis of gradation and composition, the conditions of different compactness and water content were studied by using a self-developed large-scale shear mechanical testing machine for soil rock mixture and an island reef in Nansha, China. The results show that:(1)The increase of water content leads to the decrease of shear strength, which has a negative correlation; the increase of compactness leads to the increase of shear strength, which has a positive correlation; (2)The influence of water content on the angle of internal friction is significant, showing a negative correlation. When the water content is greater than 10%, the angle of internal friction decreases slightly; when the density is 90%, the water content is greater than 5%, and the cohesion decreases slightly; (3)The influence of the compactness on the cohesion of the coral sand is not obvious, and the influence of the compactness on the angle of internal friction is significant, when the water content is greater than 5%, with the increase of the compactness internal friction angle increases significantly; (4)Under the high load, the influence of water content and compactness on the shear mechanical properties of sand is significant. The sand with small water content and large compactness has the strongest shear properties, which is of guiding significance for the design of the island filling project and the modification of site conditions.
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图 1 不同粒径吹填珊瑚砂筛分试验
Figure 1. Screening test of different particle size reclamation coral sand
图 2 吹填珊瑚砂不同粒组质量百分比
Figure 2. Mass percentage of different particle groups of reclamation coral sand
图 4 大型土石混合体力学试验机试验仪器系统结构图
1.滚动隔膜；2.活塞；3.活塞杆；4.轴承；5.加压板；6.第一活动千斤顶；7.第一固定螺栓；8.第一液压电机；9.第二液压电机；10.垂直位移传感器；11.试样框架；12.机械框架；13.第二活动千斤顶；14.上部分土石混合体；15.第二固定螺栓；16.水平位移传感器；17.滑动试样盒；18.下部分土石混合体；19.滚珠轴排；20.第一压力传感器；21.第二压力传感器
Figure 4. Test instrument system
图 5 大型土石混合体力学试验机
Figure 5. Large-scale mechanical testing machine for soil-rock mixture
图 7 80%密实度情况下抗剪强度-法向应力图
Figure 7. Shear strength versus normal stress diagram under 80% compactness
图 8 90%密实度条件下抗剪强度-法向应力图
Figure 8. Shear strength versus normal stress diagram under 90% compactness
图 9 80%密实度条件下不同含水量抗剪强度变化
Figure 9. Change of shear strength with different moisture contents under 80% compactness
图 10 90%密实度条件下不同含水量抗剪强度变化
Figure 10. Change of shear strength with different moisture contents under 90% compactness
图 11 不同密实度吹填珊瑚砂黏聚力与含水量关系曲线
Figure 11. Relationship between cohesion and water content of coral sand with different compactions
图 12 不同密实度吹填珊瑚砂内摩擦角与含水量关系曲线
Figure 12. Relationship between the angle of internal friction and water content of coral sand with different compactions
表 1 珊瑚砂基本物理参数
Table 1. Basic physical parameters of the coral sand
d60
/mmd30
/mmd10
/mm比重
GsCu
(d60/d10)Cc
(d302/d60×d10)2.0 0.5 0.25 2.70 8 0.5 
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表 2 密实度80%不同含水量珊瑚砂C、φ值
Table 2. C and φ value of coral sand with different water contents when compactness is 80%
抗剪
指标0含水量
(干燥)5%
含水量10%
含水量15%
含水量C/MPa 0.361 0.316 0.474 0.331 φ/(°) 62.52 56.53 50.90 49.89
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表 3 密实度90%不同含水量珊瑚砂C、φ值
Table 3. C and φ value of coral sand with different water contents when compactness is 90%
抗剪
指标0含水量
(干燥)5%
含水量10%
含水量15%
含水量C/MPa 0.391 0.316 0.301 0.30 φ/(°) 65.09 57.82 57.81 56.08
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