地震波频率对岩质斜坡加速度动力响应规律的影响

 斜坡在地震作用下的动力响应是地震波各频率组分与斜坡体共同作用的结果，不同的地震波频率将产生不同的斜坡响应。依托于振动台模型试验，针对均质和层状结构模型斜坡，首先分析试验不同阶段白噪声激振下的动力特性，得出两模型斜坡的共振频率呈现降低趋势，模型内部结构趋于松散，且水平向加速度的第1阶共振频率要低于竖直向加速度的第1阶共振频率。着重分析斜坡加速度动力响应规律及其与地震波频率变化的相关性，结果表明：(1) 两模型的水平向加速度响应在相对坡底高程(h/H＞1/2)时具有明显的高程放大效应，竖直向加速度响应的高程放大效应出现在h/H＜3/4的部位，且这一特征与激振频率的大小无关；(2) 在同等激振强度下，随着激振频率增大，越靠近模型斜坡的共振频率，两模型斜坡水平向加速度的响应程度也越高，而竖直向加速度响应强度与激振频率的相关性因模型斜坡结构不同而异；(3) 激振强度增加时伴随的模型结构恶化(即共振频率降低)并不一定导致加速度响应强度的减弱，相反，高频激振波由于更加接近模型的共振频率，使得响应减弱的可能性变小；(4) 层状结构模型斜坡的加速度响应强度大于均质结构模型斜坡，当激振强度较大时，这种层状结构效应与激振频率的相关性增强，表现为随着激振频率增大，该效应对水平向加速度而言逐渐明显，对竖直向加速度而言则相对减弱。

EFFECT OF FREQUENCY OF SEISMIC WAVE ON ACCELERATION RESPONSE OF ROCK SLOPES

Slope dynamic response to an earthquake is a product of interaction between seismic waves of complex frequencies and slope body；different frequency components induce different slope responses. Through shaking table tests，effect of wave frequency on two model slopes is analyzed. The two model slopes are composed of the same materials of high strength，but different structures，isotropic and layered. Firstly，dynamic characteristics of model slopes calculated through excitations of white noises show that，resonance frequency of each model decreases and the internal structure becomes loose as the test is going on；and the first resonance frequency of horizontal component acceleration is larger than that of vertical component acceleration. Then，emphasis is put on the slope acceleration responses and their correlations with changing frequencies. Results show that：(1) Obvious topographic amplification occurs in relative elevation h/H＞1/2 for horizontal component acceleration；while topographic amplification occurs in relative elevation h/H＜3/4 for vertical component acceleration；and the phenomena are independent of the excitation frequency. (2) Under the same excitation intensity，the horizontal component motion produces stronger response as the excitation frequency is increasing，more close to the resonance frequency. The correlation between vertical component response and frequency depends on the structure of model slope. (3) When the excitation intensity increases，the decay of slope structure (i.e. decease of resonance frequency) does not always cause attenuation of response，instead，high frequency excitation still can produce strong response due to the narrowing gap between excitation frequency and resonance frequency. (4) The layered model slope responses more severely than the isotropic model slope. Under strong motion，the structure effect is intensified for horizontal component and weakened for vertical component as excitation frequency increases.