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Penetration Resistance of Skirt-Tip with Rough Base for Suction Caissons in Clay

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China Ocean Engineering 2020年第6期34卷 784-794页

作者： WU Yu-qi li da-yong YANG Qing State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China College of Civil Engineering Fuzhou UniversityFuzhou 350108China College of Civil Engineering and Architecture Shandong University of Science and TechnologyQingdao 266590China

Suction caissons can readily penetrate into the seabed under the combination of the self-weight and suction resulted from the encased water being increasingly pumped out. During suction-assisted penetration, the equivalent overburden at the skirt-tip level outside the caisson is generally higher than that inside because the vertical stress within the soil plug is reduced by the exerted suction. This may result in a uniform shear stress developing over the base of the skirt-tip as the soil below the skirt-tip tends to move into the caisson, which leads to an asymmetric failure wedge existing below the base of the skirt-tip. Besides, different adhesion factors along the inside(αi) and outside(αo) of the skirt wall will cause asymmetric plastic zones inside and outside the caisson. Accordingly, an asymmetric failure mechanism is therefore proposed to calculate the penetration resistance of the skirt-tip. The proposed failure mechanism is the first to consider the effect of different adhesion factors(αi) and(αo) on the failure mechanism at the skirt-tip, and involves the contribution from the weighted average of equivalent overburdens inside and outside caisson at the skirt-tip level. The required suction pressure can be obtained in terms of force equilibrium of the caisson in a vertical direction. Finally, the asymmetric failure mechanism at the skirt-tip is validated with the FE calculations. By comparing with the measured data, the predictions of the required suction pressure are found to be in good agreement with the experimental results.

关键词： suction caisson required suction pressure penetration resistance skirt-tip rough base clay

Experimental Studies on Extraction of Modified Suction Caisson (MSC) in Sand by Reverse Pumping Water

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China Ocean Engineering 2021年第2期35卷 272-280页

作者： HUANG ling-xia ZHANG Yu-kun li da-yong College of Civil Engineering Fuzhou UniversityFuzhou 350108China Key Laboratory of Civil Engineering Disaster Prevention and Mitigation Shandong University of Science and TechnologyQingdao 266590China

A suction caisson can be extracted by applying reverse pumping water,which cannot be regarded as the reverse process of installation because of the dramatically different soil−structure interaction *** tests were first carried out in this study to investigate the extraction behavior of the modified suction caisson(MSC)and the regular suction caisson(RSC)in sand by reverse pumping *** effects of the installation ways(suction-assisted or jacking installation)and the reverse pumping rate on the variations of the over-pressure resulting form reverse pumping water were *** was found that neither the RSC nor the MSC can be fully extracted from *** the maximum extraction displacement is obtained,the hydraulic gradient of the sand in the suction caisson reaches the critical value,leading to seepage *** addition,the maximum extraction displacement decreases with the increasing reverse pumping *** the same reverse pumping rate,the final extraction displacements for the RSC and MSC installed by suction are lower than those for the RSC and MSC installed by *** final extraction displacement of MSC is almost equal to that of the RSC with the same internal compartment *** on the force equilibrium,a method of estimating the maximum extraction displacement is *** has been proved that the proposed method can rationally predict the maximum extraction displacement and the corresponding over-pressure.

关键词： modified suction caisson(MSC) model test extraction critical hydraulic gradient maximum extraction displacement

Earth Pressure Distribution and Sand Deformation Around Modified Suction Caissons(MSCs) Under Monotonic Lateral Loading

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China Ocean Engineering 2019年第2期33卷 198-206页

作者： li da-yong li Shan-shan ZHANG Yu-kun CHEN Fu-quan College of Civil Engineering Fuzhou University Key Laboratory of Civil Engineering Disaster Prevention and Mitigation Shandong University of Science and Technology

The modified suction caisson(MSC) is a novel type of foundation for ocean engineering, consisting of a short external closed-top cylinder-shaped structure surrounding the upper part of the regular suction caisson(RSC). The MSC can provide larger lateral bearing capacity and limit the deflection compared with the RSC. Therefore, the MSC can be much more appropriate to use as an offshore wind turbine foundation. Model tests on the MSC in saturated sand subjected to monotonic lateral loading were carried out to investigate the effects of external structure sizes on the sand surface deformation and the earth pressure distribution along the embedded depth. Test results show that the deformation range of the sand surface increases with the increasing width and length of the external structure. The magnitude of sand upheaval around the MSC is smaller than that of the RSC and the sand upheaval value around the MSC in the loading direction decreases with the increasing external structure dimensions. The net earth pressure in the loading direction acting on the internal compartment of the MSC is smaller than that of the RSC at the same embedded depth. The maximum net earth pressure acting on the external structure outer wall in the loading direction is larger than that of the internal compartment, indicating that a considerable amount of the lateral load and moment is resisted by the external skirt structure.

关键词： MSC (modified suction caisson) RSC (regular suction caisson) model tests monotonic lateral loading deformation of sand surface earth pressure distribution

Lateral Bearing Capacity of Modified Suction Caissons Determined by Using the limit Equilibrium Method

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China Ocean Engineering 2018年第4期32卷 461-466页

作者： li da-yong MA Shi-li ZHANG Yu-kun CHEN Fu-quan College of Civil Engineering Fuzhou University Key Laboratory of Civil Engineering Disaster Prevention and Mitigation Shandong University of Science and Technology

The modified suction caisson(MSC) adds a short-skirted structure around the regular suction caissons to increase the lateral bearing capacity and limit the deflection. The MSC is suitable for acting as the offshore wind turbine foundation subjected to larger lateral loads compared with the imposed vertical loads. Determination of the lateral bearing capacity is a key issue for the MSC design. The formula estimating the lateral bearing capacity of the MSC was proposed in terms of the limit equilibrium method and was verified by the test results. Parametric studies on the lateral bearing capacity were also carried out. It was found that the lateral bearing capacity of the MSC increases with the increasing length and radius of the external skirt, and the lateral bearing capacity increases linearly with the increasing coefficient of subgrade reaction. The maximum lateral bearing capacity of the MSC is attained when the ratio of the radii of the internal compartment to the external skirt equals 0.82 and the ratio of the lengths of the external skirt to the internal compartment equals 0.48, provided that the steel usage of the MSC is kept constant.

关键词： modified suction caissons(MSCs) lateral bearing capacity limit equilibrium method parametric studies

Studies on Suction-Assisted Installation Behavior of Suction Caissons in Clay Under Various Undrained Shear Strengths

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China Ocean Engineering 2023年第6期37卷 989-999页

作者： li da-yong HOU Xin-yu ZHANG Yu-kun MA Shi-li li Shan-shan Key Laboratory of Civil Engineering Disaster Prevention and Mitigation Shandong University of Science and TechnologyQingdao 266590China College of Pipeline and Civil Engineering China University of Petroleum(East China)Qingdao 266580China College of Civil Engineering Weifang UniversityWeifang 261061China

Suction caissons are widely used for anchoring floating platform and offshore wind *** of the suction caisson into the desired position under the combination of its self-weight and applied suction resulted from pumping out the encased water is integral to practical *** tests were carried out to investigate the suctionassisted installation of suction caissons in clay under various undrained shear *** was found that there exists a critical penetration depth *** the penetration depth is smaller than the critical value,the soil plug undrained shear strength is higher than intact clay(i.e.,clay prior to installation).However,when the penetration depth is greater than the critical penetration depth,the undrained shear strength of soil plug is lower than intact *** critical value decreases with the increasing consolidation time and undrained shear strength of *** suction-assisted installation,cracks occur around suction *** installation way has little effect on the crack *** influence range(i.e.,the maximum distance between the crack and the suction caisson edge)was found to increase with the increasing friction coefficient of interface between the suction caisson wall and soil and decreases with the increasing soil undrained shear *** addition,the drained condition of the clay during installation is dominated by the caisson aspect ratio,the undrained shear strength and the friction coefficient between the caisson wall and *** to estimate the penetration resistance and the required suction to install the suction caisson are summarized.

关键词： suction caisson suction-assisted installation model tests undrained shear strength of clay soil deformation

Resistance Factor of Caisson-Tip with Internal Fillet for Suction Caissons Penetrating into Clay

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China Ocean Engineering 2023年第3期37卷 525-532页

作者： WU Yu-qi li da-yong ZHANG Yu-kun ZHANG Yu li Shan-shan College of Pipeline and Civil Engineering China University of Petroleum(East China)Qingdao 266580China College of Civil Engineering and Architecture Shandong University of Science and TechnologyQingdao 266590China Weifang Key Laboratory of Coastal and Offshore Engineering Weifang UniversityWeifang 261061China

This paper presents failure mechanisms of the soil at the caisson-tip with fillet during suction-assisted penetration of suction caissons in undrained *** solutions of resistance factor N_c of the caisson-tip are obtained in terms of the caisson-tip geometry ratio of the flat section of the caisson-tip to the caisson wall thickness m/t and adhesion factorsα_i along inside of caisson wall andα_b at the base of the *** is indicated that the factor N_c increases with the increase of m/t,α_i and a_*** resistance factors N_c for the rough base(α_b=1)are larger by 0.57than that for the smooth base(α_b=0).Besides,the factors N_c of caisson-tip with flat base(m=t)are larger by 1.14 than that with full internal fillet(m=0).The required suction to penetrate suction caissons with various fillets is obtained in terms of the force equilibrium in vertical *** finite element limit analysis and centrifuge model test results are used to verify the rationality of the presented failure mechanisms and theoretical predictions.

关键词： suction caissons suction-assisted penetration internal fillet resistance factor undrained clay

A Modified Model for Soil–Structure Interface Considering Random damage of Mesoscopic Contact Elements

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China Ocean Engineering 2023年第5期37卷 807-818页

作者： KE li-jun GAO Yu-feng ZHAO Zi-hao li da-yong JI Jian Institute of Geotechnical Engineering Yangzhou UniversityYangzhou 225127China Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai UniversityNanjing 210098China School of Civil Engineering Shenyang Jianzhu(Architecture and Engineering)UniversityShenyang 110819China College of Pipeline and Civil Engineering China University of Petroleum(East China)Qingdao 266580China

The interaction between soil and marine structures like submarine pipeline/pipe pile/suction caisson is a complicated geotechnical mechanism *** this study,the interface is discretized into multiple mesoscopic contact elements that are damaged randomly throughout the shearing process due to the natural *** evolution equation of damage variable is developed based on the Weibull function,which is able to cover a rather wide range of distribution shapes by only two parameters,making it applicable for varying ***,a statistical damage model is established by incorporating Mohr–Coulomb strength criterion,in which the interfacial residual strength is considered whereby the strain softening behavior can be described.A concept of“semi-softening”characteristic point on shear stress–displacement curve is proposed for effectively modeling the evolution of strain ***,a series of ring shear tests of the interfaces between fine sea sand and smooth/rough steel surfaces are *** predicted results using the proposed model are compared with experimental data of this study as well as some results from existing literature,indicating that the model has a good performance in modeling the progressive failure and strain softening behavior for various types of soil–structure interfaces.

关键词： soil–structure interface statistical damage model mesoscopic element Weibull function “semi-softening”characteristic point

Repetitive DNA Sequences in Wheat and Its Relatives

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Agricultural Sciences in China 2001年第1期 5-13页

作者： ZHANG Xue-yong li da-yong ICGR of Chinese Academy of Agricultural Sciences Key Laboratory of Crop Germplasm Resources & BiotechnologyMinistry of Agoriculture Beijing 100081 College of Life Science Beijing University Beiing 100871

Repetitive DNA sequences form a large portion of eukaryote genomes. Using wheat ( Triticum )as a model, the classification, features and functions of repetitive DNA sequences in the Tritieeae grass tribe is reviewed as well as the role of these sequences in genome differentiation, control and regulation of homologous chromosome synapsis and pairing. Transposable elements, as an important portion of dispersed repetitives,may play an essential role in gene mutation of the host. Dynamic models for change of copy number and sequences of the repetitive family are also presented after the models of Charlesworth et al. Application of repetitive DNA sequences in the study of evolution, chromosome fingerprinting and marker assisted gene transfer and breeding are described by taking wheat as an example.

关键词： Wheat Genome Repetitive DNA sequence Evolution Chromosome fingerprint Marker-assisted breeding

铸造生产过程在线快速检测技术研究及应用进展

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铸造 2022年第5期71卷 517-543页

作者：李大勇哈尔滨理工大学材料科学与化学工程学院

随着智能铸造、绿色铸造步伐的不断加快，铸造生产过程检测技术特别是在线检测技术的重要性愈加突出。为了进一步提高我国铸造检测技术研究及应用水平，服务智能铸造车间构建，本文综述了合金熔体质量、型砂及砂型质量、铸件质量三大方... 详细信息

随着智能铸造、绿色铸造步伐的不断加快，铸造生产过程检测技术特别是在线检测技术的重要性愈加突出。为了进一步提高我国铸造检测技术研究及应用水平，服务智能铸造车间构建，本文综述了合金熔体质量、型砂及砂型质量、铸件质量三大方面的检测与监测技术的研究及应用进展概况，简要分析了主要在线检测技术的发展趋势。

关键词：智能铸造在线检测快速检测研究应用进展