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Dynamic Behavior of Gravity Retaining Walls with Coral Sand Backfill Under Earthquakes:Shaking Table Tests

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China Ocean Engineering 2022年第6期36卷 839-848页

作者： ZHANG Yan-ling WANG Cheng-long ding xuan-ming WU Qi College of Civil Engineering Taiyuan University of TechnologyTaiyuan 030024China Key Laboratory of New Technology for Construction of Cities in Mountain Area School of Civil EngineeringChongqing UniversityChongqing 400045China

The retaining walls in coral sand sites are inevitably threatened by earthquakes. A series of shaking table tests were carried out to study the seismic stability of gravity retaining walls with coral sand backfill. Parallel tests with quartz sand were performed to compare and discuss the special dynamic properties of coral sand sites. The results show that the acceleration difference between the retaining wall and the coral sand backfill is 76%-92% that of the quartz sand,which corresponds to the larger liquefaction resistance of coral sand compared with the quartz sand. However, the horizontal displacement of the retaining walls with coral sand backfill reaches 79% of its own width under 0.4g vibration intensity. The risk of instability and damage of the retaining walls with coral sand backfill under strong earthquakes needs attention.

关键词： coral sand seismic response liquefaction shaking table test gravity retaining walls

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 *** this paper,expansive concrete pile is utilized to improve the bearing capacity of pile foundations in coral *** model tests and numerical simulation are performed to reveal the bearing mechanism of expansive concrete pile in coral *** showed that the lateral earth pressure near pile increases obviously and the side friction of piles is improved,after adding expansion agent to the *** horizontal linear expansion is 1.11%and the bearing capacity increased 41%for the pile,when 25%expansion agent is *** in finite element numerical simulation also show that ultimate bearing capacity increases with the increase of the linear expansion ***,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 ***,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 *** 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 *** 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 *** acceleration response of the soil increases with the increase of the slope *** slope displacement presents substantial increments as the excess pore pressure ratio *** addition,the lateral movement,and slope settlement present substantial increments as the slope angle *** liquefaction is observed under a dynamic excitation of 0.2 g in the coral sand *** 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 *** 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°*** lateral movement of the slope surface near the water level line is substantially larger than that away from the water *** largest settlement is observed near the middle section of the slope(below the water level)under a dynamic excitation of 0.2 *** 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

Vertical vibration of a large diameter pipe pile considering transverse inertia effect of pile

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Journal of Central South University 2016年第4期23卷 891-897页

作者：郑长杰刘汉龙丁选明周航 Key Laboratory of New Technology for Construction of Cities in Mountain Area (Chongqing University) Chongqing 400045 China

Considering the transverse inertia effect of pile, the vertical soil layer is studied. The wave propagations in the outer and inner soil dynamic response of a large diameter pipe pile in viscoelastic are simulated by three-dimensional elastodynamic theory and those in the pile are simulated by Rayleigh-Love rod theory. The vertical and radial displacements of the outer and inner soil are obtained by utilizing Laplace transform technique and differentiation on the governing equations of soils. Then, based on the continuous conditions between the pile and soils, the displacements of the pile are derived. The frequency domain velocity admittance and time domain velocity response of the pile top are also presented. The solution is compared to a classical rod model solution to verify the validity. The influences of the radii and Poisson ratio of pile on the transverse inertia effect of pile are analyzed. The parametric study shows that Poisson ratio and outer radius of pile have significant influence on the transverse inertia effect of large diameter pipe piles, while the inner radius has little effect.

关键词： large diameter pipe pile vertical vibration Rayleigh-Love rod transverse inertia effect

Numerical investigation of piled raft foundation in mitigating embankment vibrations induced by high-speed trains

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Journal of Central South University 2015年第11期22卷 4434-4444页

作者：付强刘汉龙丁选明郑长杰 College of Civil and Transportation Engineering Hohai University Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering

A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds(36-432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic velo

关键词： finite element simulation track-ballast-embankment

Model test on vertical bearing capacity of X-section concrete pile raft foundation in silica sand

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Journal of Central South University 2020年第6期27卷 1861-1869页

作者： XU Lai PENG Yu ding xuan-ming LIU Jia-yi Guangdong Zhonggong Architectural Design Institute Co. Ltd.Guangzhou 510670China 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 concrete piles pile raft foundation in silica sand,a series of vertical load tests are carried *** X-section concrete piles are compared with circular section pile with the same section *** load−settlement curves,axial force and skin friction,strain on concave and convex edge of the pile,pile-sand stress ratio,distributions of side and tip resistance are *** results show that bearing capacity of the X section concrete pile raft foundation is much larger than that of the circular pile raft ***,compared with the circular pile,the peak axial force of X-section piles under raft is deeper and smaller while the neutral point of X-section concrete pile is ***,the strain on the concave edge is much larger than that on the convex edge of the pile,and the convex edge has more potential in bearing capacity as the vertical load *** X-section pile has higher pile-sand stress ratios and load-sharing between side resistance and tip *** all,the X-section concrete pile can significantly increase the bearing capacity of pile-raft foundations in silica sand.

关键词： X-section pile pile raft foundation model test neutral point pile-soil stress ratio

基于径向不变假定的变阻抗现浇大直径管桩瞬态动测响应频域解

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四川大学学报（工程科学版） 2011年第3期43卷 18-25,80页

作者：丁选明谭慧明河海大学水资源高效利用与工程安全国家工程研究中心江苏南京210098 江苏省地震工程研究院江苏南京210014

为了分析低应变检测时有缺陷的现浇混凝土大直径管桩在瞬态集中荷载作用下的动力响应问题,基于径向不变假定建立了任意段变阻抗大直径管桩的计算模型和波动方程,采用Laplace变换法求得了波动方程的频域解析解,采用Fourier逆变换求得了... 详细信息

为了分析低应变检测时有缺陷的现浇混凝土大直径管桩在瞬态集中荷载作用下的动力响应问题,基于径向不变假定建立了任意段变阻抗大直径管桩的计算模型和波动方程,采用Laplace变换法求得了波动方程的频域解析解,采用Fourier逆变换求得了时域响应。将计算结果与3维有限元、1维波动理论和3维解析解的结果进行了对比分析。研究结果表明:本文解析方法的计算结果和3维有限元结果较为接近;在90°测点,3维有限元、本文解析解和1维波动理论的速度响应差别不大。通过桩顶不同点的动力响应分析可知,入射波峰到达的时间随测点与激振点夹角不同而变化,夹角越小,到达时间越早;深度较浅缺陷反射波峰到达的时间随测点与激振点夹角而异,但达到一定深度后,缺陷反射波峰到达时间差别较小;高频干扰最小的点在夹角90°的点;对工程实测曲线的较好拟合表明该频域解析解具有一定的工程实用价值。

关键词：大直径管桩低应变检测动力响应 3维效应解析解