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首页> 外文期刊>Geotechnique >Sand response to a large number of loading cycles under zero-lateral-strain conditions: evolution of void ratio and small-strain stiffness
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Sand response to a large number of loading cycles under zero-lateral-strain conditions: evolution of void ratio and small-strain stiffness

机译：砂土在零侧向应变条件下对大量载荷循环的响应：空隙率和小应变刚度的演变

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摘要

Geotechnical structures often experience a large number of repetitive loading cycles. This research examines the quasi-static mechanical response of sands subjected to repetitive loads under zero-lateral-strain boundary conditions. The experimental study uses an automatic repetitive loading frame operated with pneumatic pistons. Both vertical deformation and shear wave velocity are continuously monitored during 10 000 repetitive loading cycles. The void ratio evolves towards the terminal void ratio e(T) as the number of load cycles increases. The terminal void ratio e(T) is a function of the initial void ratio e(0) and the stress amplitude ratio Delta sigma/sigma(0). The number of cycles N* required to reach half of the final volume contraction ranges from N* - 1 for densely packed sands (e(0)- e(min)) to N - 10(3) for loosely packed sands (e(0)- e(max)). As the soil approaches terminal density at a large number of cycles, peak-to-peak strains are dominated by elastic deformations, and the minute plastic strains that remain in every cycle reflect local and sequential contact events. The shear wave velocity increases during cyclic loading with data suggesting a gradual increase in the coefficient of earth pressure K-0 during repetitive loading. Changes in shear wave velocity track the evolution of the constrained modulus M; in fact, the constrained modulus can be estimated from the shear wave velocity to compute soil deformation in a given cycle. A simple procedure is suggested to estimate the potential settlement a layer may experience when subjected to repetitive mechanical loads.
机译：岩土结构经常经历大量的重复加载循环。本研究研究了在零侧应变边界条件下承受重复载荷的砂土的准静态力学响应。实验研究使用了带有气动活塞的自动重复加载框架。在10000次重复加载周期中，垂直变形和剪切波速度都得到连续监测。随着负载循环数的增加，空隙率朝着末端空隙率e（T）发展。末端空隙率e（T）是初始空隙率e（0）和应力振幅比Delta sigma / sigma（0）的函数。达到最终体积收缩一半的循环所需的循环数N *从N *-> 1（对于密堆积的沙子）（e（0）-> e（min））到N-> 10（3）（对于松散堆积的沙子） （e（0）-> e（max））。随着土壤在大量循环中接近末端密度，峰-峰值应变主要由弹性变形控制，每个循环中残留的微小塑性应变反映了局部和顺序的接触事件。剪切波速度在循环加载过程中增加，数据表明在重复加载过程中土压力系数K-0逐渐增加。剪切波速度的变化跟踪了约束模量M的演化；实际上，受约束的模量可以从剪切波速度估算出来，以计算给定周期内的土壤变形。建议使用一个简单的程序来估算一层在承受重复的机械载荷时可能遇到的潜在沉降。

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