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层状地基中海洋大直径管桩水平动力响应分析

岩土力学 2024年第6期45卷 1873-1883页

作者：林浩郑长杰丁选明福建理工大学福建省土木工程新技术与信息化重点实验室福建福州350118 福建理工大学土木工程学院福建福州350118 重庆大学土木工程学院重庆400045

考虑桩−海水−层状土相互作用,研究了水平动荷载作用下层状地基中海洋大直径管桩的动力响应特性。将海水视为无黏性可压缩流体介质建立桩周、桩芯海水的运动方程,通过分离变量法并结合海水的边界条件求得桩周、桩芯海水作用在管桩上的动... 详细信息

考虑桩−海水−层状土相互作用,研究了水平动荷载作用下层状地基中海洋大直径管桩的动力响应特性。将海水视为无黏性可压缩流体介质建立桩周、桩芯海水的运动方程,通过分离变量法并结合海水的边界条件求得桩周、桩芯海水作用在管桩上的动水压力。将海床土体视为黏弹性介质并考虑其成层非均质性,利用微分变化并结合土体振动边界条件解得桩周、桩芯土体作用在管桩上的水平抗力。进而根据各桩段上水平力的平衡建立管桩控制方程,利用传递矩阵法并结合桩身的连续条件以及桩顶、桩底的边界条件,得到层状海床土中海洋大直径管桩的水平动力响应解析解,给出了桩顶位移解析表达式。将所得解与有限元模拟结果以及退化解与已有文献解进行对比,验证了本研究计算方法的合理性。并基于所得解分析了管桩−海水−层状土系统水平动力响应对动水压力、水深、土体模量、土层厚度等关键参数的敏感性。

关键词：桩顶位移海洋大直径管桩水平振动特性桩芯海水层状海床地基

Application of transparent soil model tests to study the soil-rock interfacial sliding mechanism

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Journal of Mountain Science 2019年第4期16卷 935-943页

作者： WANG Zhuang LI Chi ding xuan-ming Department of Civil Engineering Inner Mongolia University of Technology Key Laboratory of New Technology for Construction of Cities in Mountain Area Ministry of Education Chongqing University

When transparent soil technology is used to study the displacement of a slope, the internal deformation of the slope can be visualized. We studied the sliding mechanism of the soil-rock slope by using transparent soil technology and considering the influence of the rock mass Barton joint roughness coefficient, angle of the soil mass, angle of the rock mass and soil thickness factors on slope stability. We obtained the deformation characteristics of the soil and rock slope with particle image velocimetry and the laser speckle technique. The test analysis shows that the slope sliding can be divided into three parts: displacements at the top, the middle, and the bottom of the slope; the decrease in the rock mass Barton joint roughness coefficient, and the increase in soil thickness, angles of the rock mass and soil mass lead to larger sliding displacements. Furthermore, we analyzed the different angles between the rock mass and soil thickness. The test result shows that the displacement of slope increases with larger angle of the rock mass. Conclusively, all these results can help to explain the soil-rock interfacial sliding mechanism.

关键词： Slope engineering Transparent soil Model test Interfacial sliding mechanism

Bearing Behavior of Cast-in-Place Expansive Concrete Pile in Coral Sand Under Vertical Loading

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China Ocean Engineering 2021年第3期35卷 352-360页

作者： ding xuan-ming DENG Wei-ting PENG Yu ZHOU Hang WANG Chun-yan Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing 400045China National Joint Engineering Research Center of Geohazards Prevention in the Reservoir Areas Department Chongqing UniversityChongqing 400045China College of Civil Engineering Chongqing UniversityChongqing 400045China

The low side friction of piles in coral sand results in the low bearing capacity of foundations.In this paper,expansive concrete pile is utilized to improve the bearing capacity of pile foundations in coral sand.Both model tests and numerical simulation are performed to reveal the bearing mechanism of expansive concrete pile in coral sand.Results showed that the lateral earth pressure near pile increases obviously and the side friction of piles is improved,after adding expansion agent to the concrete.The horizontal linear expansion is 1.11%and the bearing capacity increased 41%for the pile,when 25%expansion agent is added.Results in finite element numerical simulation also show that ultimate bearing capacity increases with the increase of the linear expansion ratio.Besides,the area for obvious increase in side friction is below the surface of soil about three times the pile diameter,and the expansion leads to a high side friction sharing of the pile.Therefore,the cast-in-place expansive concrete pile is effective in improving the bearing capacity of piles in coral sand.

关键词： bearing behavior expansive concrete pile coral sand side friction numerical simulation

Effects of topography on dynamic responses of single piles under vertical cyclic loading

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Journal of Mountain Science 2020年第1期17卷 230-243页

作者： QU Li-ming ding xuan-ming WU Chong-rong LONG Yong-hong YANG Jin-chuan College of Civil Engineering Chongqing UniversityChongqing 400045China Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing 400045China Citation:Qu LMDing

This paper describes model tests of single piles subjected to vertical cyclic compressive loading for three kinds of topography: sloping ground, level ground, and inclined bedrock. Comprehensive dynamic responses involving cyclic effects and vibration behaviours are studied under various load combinations of dynamic amplitude, mean load,frequency and number of cycles. Test results show that permanent settlement can generally be predicted with a quadratic function or power function of cycles.Sloping ground topography produces more pronounced settlement than level ground under the same load condition. For vibration behaviour,displacement amplitude is weakly affected by the number of cycles, while load amplitude significantly influences dynamic responses. Test results also reveal that increasing load amplitude intensifies nonlinearity and topography effects. The strain distribution in a pile and soil stress at the pile tip are displayed to investigate the vibration mechanism accounting for sloping ground effects. Furthermore, the dynamic characteristics among three kinds of topography in the elastic stage are studied using a three-dimensional finite method. Numerical results are validated by comparing with experimental results for base inclination topography. An inclined soil profile boundary causes non-axisymmetric resultant deformation, though a small difference in vertical displacement is observed.

关键词： Pile Model test Dynamic response Permanent settlement Vibration displacement Topography effects

Performance of X-Section Concrete Pile Group in Coral Sand Under Vertical Loading

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China Ocean Engineering 2020年第5期34卷 621-630页

作者： PENG Yu LIU Jia-yi ding xuan-ming FANG Hua-qiang JIANG Chun-yong College of Civil Engineering Chongqing UniversityChongqing 400045China Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing 400045China CCTEG Chongqing Engineering Co. LtdGeotechnical Engineering InstituteChongqing 400042China

To reveal the bearing capacity of the X-section pile group in coral sand, a series of model load tests are conducted.The testing results are presented as load-settlement curves, pile-soil stress ratios, distributions of side friction and axial force, and load-sharing ratio between side and tip resistances. The reliability and accuracy of the numerical simulation model are verified by comparing the results of the model test. Comparative analysis between X-section and circular section piles with the same cross-sectional area indicates that the bearing capacity of the X-section pile group is much larger than that of the circular pile group. The axial force of X-section piles is smaller while the peak skin friction is larger than that of circular piles at the same depth. The skin friction of the core pile is the largest,followed by the side pile and the corner pile is the smallest when the load is relatively small;however, it is converse when the load is larger than 10 k N. Compared with piles in silica sand, the pile in coral sand has a lower bearing capacity, and the sand breakage leads to the steep drop failure of pile foundation. Moreover, pile positions under the raft have less effect on the load-share differences among corner, side and core piles in coral sand. This study provides a reference for the construction of pile foundations in coral sand.

关键词： X-section pile group coral sand model test numerical analysis pile-soil stress ratio

Seismic responses of slopes with different angles in coral sand

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Journal of Mountain Science 2021年第9期18卷 2475-2485页

作者： ZHANG Yan-ling ding xuan-ming CHEN Zhi-xiong WU Qi WANG Cheng-long College of Civil Engineering Taiyuan University of TechnologyTaiyuan 030024China College of Civil Engineering Chongqing UniversityChongqing400045China Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing400045China

This paper investigates the seismic responses of slopes in coral sand taken from a reef island in the South China Sea.A series of shaking table model tests were conducted to explore the responses of soil acceleration,excess pore pressure,and slope displacement for three slope angles(5°,10°,and 15°).The results show that the excess pore pressure ratio of the slope decreases due to an increase in the initial shear stress when the slope angle increases.The acceleration response of the soil increases with the increase of the slope angle.The slope displacement presents substantial increments as the excess pore pressure ratio increases.In addition,the lateral movement,and slope settlement present substantial increments as the slope angle increases.No liquefaction is observed under a dynamic excitation of 0.2 g in the coral sand site.Under a dynamic excitation of 0.4 g,the site liquefies quickly,the acceleration amplification factor decreases,and the lateral movement and the settlement of the slope surface both increase compared with that under 0.2 g excitation.For the slope with an angle of 15°at 0.4 g,the flow distance of the sand strip increase by 289.47%compared with that in the 5°case.The lateral movement of the slope surface near the water level line is substantially larger than that away from the water line.The largest settlement is observed near the middle section of the slope(below the water level)under a dynamic excitation of 0.2 g.In contrast,the largest settlement under a dynamic excitation of 0.4 g occurs at the top of the slope.

关键词： Coral sand Slope angle Shaking table tests Seismic response Liquefaction

基于CEL法的砂土中相邻XCC桩贯入对既有XCC单桩影响的研究

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中国公路学报 2024年第4期37卷 141-154页

作者：周鹏夏良利刘汉龙徐长节崔杰曹光伟丁选明华东交通大学土木建筑学院江西南昌330013 广州大学工程抗震研究中心广东广州510006 重庆大学土木工程学院重庆400045 福州大学紫金地质与矿业学院福建建福州350116

目前现浇X形桩(XCC桩)的研究主要集中于黏土地基,而对于砂土中XCC桩的相关研究却很少;此外,在研究XCC桩贯入问题时,主要分析的是沉桩挤土效应,而忽略了实际工程施工中挤土位移荷载会对邻近既有桩产生附加桩身响应这一关键问题。为此,利... 详细信息

目前现浇X形桩(XCC桩)的研究主要集中于黏土地基,而对于砂土中XCC桩的相关研究却很少;此外,在研究XCC桩贯入问题时,主要分析的是沉桩挤土效应,而忽略了实际工程施工中挤土位移荷载会对邻近既有桩产生附加桩身响应这一关键问题。为此,利用耦合的欧拉-拉格朗日(CEL)大变形数值技术,建立了相邻贯入XCC桩-砂土-既有XCC桩的整体CEL有限元数值模型,并且将数值结果与室内模型试验测量数据进行比较,验证了CEL数值技术在分析相邻XCC桩-土体-既有XCC桩相互作用的可行性和有效性。然后,开展了一系列参数研究,探讨了贯入深度、相邻桩与既有桩的间距、既有桩桩头边界条件等因素对既有桩侧向响应的影响。最后,基于参数分析的结果,编制了一套可用于岩土工程师在设计初期阶段评估相邻XCC桩贯入引起的既有XCC桩最大侧向响应的设计图,以减轻桩基施工带来的相关风险。

关键词：路基工程 XCC桩 CEL大变形数值技术砂土侧向响应设计图

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砂土中能量桩单桩水平承载特性模型试验研究

工程力学 2024年第3期41卷 114-123页

作者：陈志雄赵华王成龙丁选明孔纲强高学成重庆大学土木工程学院重庆400045 河海大学土木与交通学院江苏南京210098 重庆大学产业技术研究院重庆401329

为探究能量桩单桩水平承载特性,针对砂土中能量桩在水平荷载下的承载特性进行研究,基于模型试验,分析了水平荷载作用下能量桩在制冷和加热过程中的桩顶位移、桩前土压力以及桩身弯矩等的变化规律。研究结果表明:制冷会引起能量桩桩顶水... 详细信息

为探究能量桩单桩水平承载特性,针对砂土中能量桩在水平荷载下的承载特性进行研究,基于模型试验,分析了水平荷载作用下能量桩在制冷和加热过程中的桩顶位移、桩前土压力以及桩身弯矩等的变化规律。研究结果表明:制冷会引起能量桩桩顶水平位移略微增大,增量为0.48%D(D为桩体直径),而加热会引起较大的桩顶水平位移,达到了2.38%D;制冷和加热在初始阶段会引起桩前土压力增大,初始增长阶段结束后,土压力变化较小,多为缓慢增长或基本不变。相较于初始土压力,制冷和加热结束时的土压力基本呈增长趋势,仅个别埋深处土压力减小。制冷过程中,埋深0%L~40%L(L为有效桩长)范围内的弯矩增大,埋深40%L~100%L位置处的弯矩变化较小;加热过程中,埋深0%L~60%L范围内的弯矩均有所增大,0%L~40%L位置处的弯矩增大最为明显。制冷和加热过程中均在20%L处产生了最大弯矩,最大弯矩的增加量分别为9.93%和10.32%。进一步基于圆孔扩张理论提出了弯矩计算的理论解,并与试验结果进行对比分析,理论计算值与实测值较为吻合。

关键词：能量桩水平承载特性模型试验砂土圆孔扩张理论

Comparative study of shaking table model tests on seismic behavior of underground structures in coral sand and quartz sand sites

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Yantu Lixue/Rock and Soil Mechanics 2020年 41卷 357-366页

作者： Zhang, Yan-Ling ding, xuan-ming Wu, Qi Wang, Cheng-Long Chen, Zhi-Xiong Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing University Chongqing 400045 China College of Civil Engineering Chongqing University Chongqing 400045 China

In order to reveal the seismic performance of underground structures in coral sand site, shaking table tests of the dynamic response of underground structures in the coral sand site under two excitation intensities were carried out and compared with the quartz sand site. The results show that with the increase of ground motion intensity, the excess pore pressure ratio, horizontal dynamic earth pressure and strain response of the two sites increase, and the separation between the structure and the surrounding soil is more obvious. The coral sand site has a lower excess pore pressure ratio than that in the quartz sand site, about 42.61%-67.35% of the quartz sand site. The peak acceleration of coral sand site is less than quartz sand site. The horizontal dynamic soil pressure response of the two kinds of sand sites shows a "Z" shaped distribution along the depth, and the horizontal dynamic soil pressure of the coral sand site is less than that of the quartz sand site. On the inner and outer surface of the same wallboard of the underground structure, the strain appears to be large at the corners and small at the midpoints. The strain in the coral sand site is smaller than that of the quartz sand site. With the increase of shaking input intensity, the uneven ground settlement is more obvious, the uneven ground settlement of quartz sand site is higher than that of coral sand site. © 2020, Science Press. All right reserved.

关键词： Sand