基于离心振动台的堆积型滑坡加速度响应特征

 加速度响应规律是解释滑坡震害、合理确定地震影响系数的基础。为此，设计完成了50倍重力加速度条件下的堆积型滑坡离心振动台模型试验，用来研究堆积型滑坡的加速度响应特征及规律。模型滑坡放置于600 mm×400 mm×500 mm(L×W×H)的刚性模型箱内，采用汶川地震清溪台站反演的基岩波作为基底输入，调整其幅值，研究不同强度地震动作用下堆积型滑坡的加速度响应特征及规律。试验结果表明：坡面水平向和竖直向峰值加速度(PGA)放大系数随滑坡的高程增加而增大，趋于坡顶时，增速明显变大，具有明显的高程放大效应；地震动作用下坡面与坡体内部的加速度响应特征明显不同，具有坡面浅表放大效应；滑床岩体自下向上水平向加速度有放大趋势，但与滑坡浅表土体相比，放大倍数则明显减弱；坡顶附近存在显著的波型转换现象；随着输入地震波强度的增大，PGA放大系数总体上表现为递减趋势。所得到的成果初步揭示了堆积型滑坡的加速度响应特征，为解释滑坡震害、确定地震影响系数等提供较可靠的依据。

ACCELERATION RESPONSE CHARACTERISTICS OF COLLUVIAL LANDSLIDE BASED ON CENTRIFUGAL SHAKING TABLE MODEL TEST

The law of acceleration response can be used to analyse landslide damage mechanisms and determine the earthquake influencing coefficient reasonably. Hence，a centrifuge shaking table model test of colluvial landslide was designed and carried out on a centrifuge shaking table at 50 gravitational accelerations in order to research its acceleration response characteristics. The model landslide was installed into a rigid aluminum alloy container with the length of 600mm，width of 400mm and height of 500mm. Bedrock wave (Qingxi wave) was inputted from the bottom of the model to study the dynamic response behavior of the colluvial landslide under earthquakes of different intensities by scaling the amplitude of the input seismic wave. And the bedrock wave was derived from the one recorded by Qingxi station during the Wenchuan earthquake. Results show that both the horizontal and vertical peak ground acceleration (PGA) amplification coefficients at landslide surface increase with the increasing height of landslide. The landslide shows an obvious elevation amplification effect，i.e.，the increasing rate of PGA amplification coefficients becomes notably larger approaching the slope crest. The acceleration response characteristics of the landslide surface and landslide body are significantly different under earthquake，which shows the surface effect. The horizontal acceleration at bedrock has amplification effect on input seismic wave along the height of the landslide，but it is weaken much weaker by comparison with that at the landslide surface. The slope crest has an obvious wave mode conversion phenomenon to the input seismic wave. The PGA amplification coefficients along landslide surface decrease with the increasing of the earthquake amplitudes. The results are helpful to reveal acceleration response characteristics of the same type of colluvial landslide under earthquake，and provided valuable references for determining the earthquake influence coefficient and analysing landslide damage mechanisms.