CDM格栅复合黏土地基地震反应离心试验研究

doi:10.13722/j.cnki.jrme.2018.0433

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摘要近期国际震害调查统计发现CDM复合地基减灾性能普遍优于预期，提升其地震响应特征及规律认识对于发展适用抗震设计方法十分重要。介绍2组CDM格栅复合黏土地基动力离心模型试验，包含1个未处理地基、3个采用原位TRD工法制作的端承型和悬浮型复合地基，分析加速度峰值放大系数、反应谱比、地表沉降、剪应力–剪应变等特征及变化。结果表明：端承型复合地基加速度反应基本呈线性且放大，平均峰值放大约1.4倍，悬浮型地基下层土体及软化对局部场地放大效应、PGA具有较强约束作用，并在高频地震中出现减震现象；各复合地基墙体沉降均规律性发生于震后再固结过程，而端承型地基墙体与墙侧土体沉降差异较大，表明产生较大负摩阻力，悬浮型地基墙体与墙侧土体沉降则高度吻合；同一深度反演求解得剪应力–剪应变响应特征，较好地验证了地表加速度分析结果，并反映了不同频率地震下土–结作用(SSI)，分别可使墙侧土体剪应变的发展受到约束和牵引作用，合理解释了高频地震过程中端承型地基墙侧土体的规律沉降现象。

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	王永志1
	2
	Mohammad Khosravi2
	Daniel W. Wilson2
	王海1
	田村修次3
	王体强1

关键词 ：土力学, CDM格栅, 动力离心试验, 场地放大效应, 地表沉降, 剪应力&ndash, 剪应变

Abstract：Recent international damage surveys indicate that the performance of ground improved by cement-deep-mixing(CDM) method is generally better than expectations. Enhancing the understanding of the seismic response of CDM improved ground is important in developing suitable design methods of seismic resistance. Two series of dynamic centrifuge model tests to the composite soft clay grounds improved by CDM grids were presented. The unimproved ground and improved ground sites with embedded and floating CDM grids installed following a TRD-like method were tested. The responses and features of peak acceleration amplification，spectral ratios，ground settlement and shear stress-strain were analyzed. The results show that the acceleration responses of two embedded grid-improved grounds are linearly amplified at large and the peak accelerations are amplified by a factor of 1.4 on average，which is in contrast to the response where a floating grid was used. The unimproved soft clay below the floating grid-improved ground significantly affects the local amplification effect and limits the surface PGA especially when the clay is softening. In this case，a reduction in high frequency content were observed. The settlements of grid walls in all cases typically occur mostly due to the post shaking reconsolidation. Differential settlements were observed between the grid walls and the enclosed soils in both embedded grid-improved ground sites，indicating that the negative skin friction was generated. Conversely，the settlements of the grid walls and the enclosed soils in the floating grid-improved ground are in agreement. The results of back analysis indicate that the grid walls by SSI(Soil-Structure Interaction) restrict or mobilize the shear strain response of their enclosed soils dependent on the frequency content and intensity of seismic motions. The effect of mobilizing gave a reasonable explanation for the settlements of the enclosed soils in the two embedded grid-improved grounds during the high frequency earthquakes.

Key words： soil mechanics CDM grid dynamic centrifuge test site amplification effect ground settlement shear stress-strain

引用本文:

王永志1，2，Mohammad Khosravi2，Daniel W. Wilson2，王海1，田村修次3，王体强1. CDM格栅复合黏土地基地震反应离心试验研究[J]. 岩石力学与工程学报, 2018, 37(10): 2394-2405.
WANG Yongzhi1，2，Mohammad Khosravi2，Daniel W. Wilson2，WANG Hai1，Shuji Tamura3，WANG Tiqiang1. Centrifuge modeling of seismic response of soft clay grounds improved by CDM grids. , 2018, 37(10): 2394-2405.

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http://www.rockmech.org/CN/10.13722/j.cnki.jrme.2018.0433 或 http://www.rockmech.org/CN/Y2018/V37/I10/2394

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