MULTI-PROBE IN-SITU TESTING SYSTEM AND EVALUATION METHOD FOR UNDRAINED SHEAR STRENGTH OF DEEP-SEA SHALLOW SEDI ̄MENTS
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摘要: 海洋工程建设已步入深海,但与之匹配的浅表层沉积物不排水剪切强度原位测试技术尚不成熟。为此,本文开发了可用于评估深海浅表层沉积物土力学性质的多探头原位测试系统,包括锥形触探仪、球形贯入仪和十字板剪切仪,可实现对深海沉积物土力学性质的快速、准确和智能化评价。进一步,通过CEL大变形数值模拟和足尺土工模型试验确定锥形触探仪的锥尖阻力系数,基于离心模型试验给出球形贯入仪的贯入阻力系数,从而完善深海浅表层沉积物不排水剪切强度的评价方法;在此基础上,探讨3种特定仪器各自适合的强度测试区间。结果表明:对于深海浅表层沉积物不排水剪切强度的评估,锥形触探仪和球形贯入仪的阻力系数建议分别取值为9.5和11.1。Abstract: Ocean engineering has moved towards the deep sea. But in-situ testing technology for undrained shear strength of deep sea shallow sediments is not yet mature. This paper develops a multi-probe in-situ test system that can evaluate the soil mechanical properties of deep-sea shallow sediments. It includes CPT, Ball Full-flow Penetrometer and VST to achieve a rapid, accurate and intelligent evaluation of the soil mechanical properties of deep-sea shallow sediments. Further the resistance coefficient of CPT is determined with CEL large-deformation numerical analysis method and the full-scale geotechnical model test, and the resistance coefficient of Ball Full-flow Penetrometer is given by the centrifugal model test. Then the undrained shear strength evaluation method of deep sea shallow sediments is improved. On this basis, the undrained shear strength test intervals suitable for each of the instruments are discussed. Results indicate that for the evaluation of the deep-sea shallow saturated soft clay undrained shear strength, the recommended penetration coefficients of CPT and Ball Full-flow Penetrometer are respectively 9.5 and 11.1.
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Key words:
- CPT /
- Ball Full-flow Penetrometer /
- VST /
- Deep sea shallow sediments /
- Undrained shear strength /
- Evaluation method /
- Test interval
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表 1 仪器尺寸及贯入或扭转参数
Table 1. Instrument size and penetration or torsion parameters
仪器类型 探头尺寸/mm 杆轴直径/mm 贯入或扭转速率 锥形触探仪 直径 DCone=35.7 35.7(探杆) 20±5mm·s-1 球形贯入仪 DBall=113 十字板
剪切仪高×直径×板厚 100×50×2 13.0(连接杆) 35.7(探杆) 12(°)/min 表 2 CEL方法模拟参数
Table 2. Parameters of CEL method
本构模型 单元类型 模型尺寸/mm 模拟工况/kPa 莫尔-库仑 EC3D8R
欧拉体
R3D3
拉格朗日体长×宽×高
17.85×17.85×53.55
细网格尺寸
0.357
粗网格尺寸
3.570.5
1.0
2.0
5.0
10.0表 3 T-bar与微型十字板剪切仪(Mini-VST)尺寸
Table 3. Size of T-bar and Mini-VST
直径/mm 长度/mm 板高/mm T-bar 6 42 — Mini-VST 10 — 20 表 4 球形贯入仪阻力系数结果
Table 4. Results of NBall
土样编号 测试深度/D 手动十字板结果/kPa 贯入阻力/kPa 阻力系数 K1-75g 2.5 2.4 25.9 10.8 K1-125g 27.0 11.3 K2-75g 2.5 3.6 39.3 10.9 K2-125g -
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