CAJ | 학술논문

2008年汶川八级地震形成了至少257个堰塞坝，主震后发生的大量余震可能会影响堰塞坝的动力安全状态。堰塞坝体的动力特性参数(包括自振频率和阻尼比等)和加速度分布规律是堰塞坝地震安全研究的基础内容。通过大型振动台模型试验，研究在余震作用下模型堰塞坝体的动力特性参数、加速度分布规律及二者的影响因素，并根据动力相似律，计算原型坝体的动力特性参数。共进行2组不同材料的振动台模型试验，分别模拟含黏粒较多且颗粒较小(坝体I)和基本不含黏粒且颗粒较大(坝体II)的2种坝体。在不同地震波形输入、不同加速度峰值和不同水位条件下进行振动台试验。研究成果表明：(1)模型坝体具有较稳定的X向和Z向自振频率和阻尼比。(2)先期振动使坝体自振频率降低，阻尼比有增大趋势；坝体I的自振频率小于坝体II。水位变化对2种坝体自振频率的影响规律不一致。(3)加速度放大倍数随高程增大而增大，最大加速度发生在坝顶处；相同高程测点加速度放大倍数最大值出现在上游或下游靠近坝坡表面处，即“表面放大”效应明显，说明坝坡表面容易受地震作用破坏。(4)所含频谱成分与坝体自振频率接近的地震波会引起最大的加速度反应。Z 向振动使坝体测点 X 向加速度放大倍数增大。加速度放大倍数一般随输入加速度峰值的增大而减小。
2008년문천팔급지진형성료지소257개언새패，주진후발생적대량여진가능회영향언새패적동력안전상태。언새패체적동력특성삼수(포괄자진빈솔화조니비등)화가속도분포규률시언새패지진안전연구적기출내용。통과대형진동태모형시험，연구재여진작용하모형언새패체적동력특성삼수、가속도분포규률급이자적영향인소，병근거동력상사률，계산원형패체적동력특성삼수。공진행2조불동재료적진동태모형시험，분별모의함점립교다차과립교소(패체I)화기본불함점립차과립교대(패체II)적2충패체。재불동지진파형수입、불동가속도봉치화불동수위조건하진행진동태시험。연구성과표명：(1)모형패체구유교은정적X향화Z향자진빈솔화조니비。(2)선기진동사패체자진빈솔강저，조니비유증대추세；패체I적자진빈솔소우패체II。수위변화대2충패체자진빈솔적영향규률불일치。(3)가속도방대배수수고정증대이증대，최대가속도발생재패정처；상동고정측점가속도방대배수최대치출현재상유혹하유고근패파표면처，즉“표면방대”효응명현，설명패파표면용역수지진작용파배。(4)소함빈보성분여패체자진빈솔접근적지진파회인기최대적가속도반응。Z 향진동사패체측점 X 향가속도방대배수증대。가속도방대배수일반수수입가속도봉치적증대이감소。
At least 257 landslide dams were formed by Wenchuan earthquake in 2008. The aftershocks occurred after the major quake may influence the safety of those landslide dams. Dynamic characteristic parameters, including natural frequency and damping ratio,and distribution of acceleration amplification factor are the focus of the research of landslide dams. This paper presents the studies of large-scale shaking table tests on the dynamic characteristics and the acceleration distribution of landslide dams under aftershocks. The natural frequency,the damping ratio and the distribution of acceleration amplification factor of a model dam and their influencing factors are studied. The dynamic characteristic parameters of prototype landslide dams are calculated according to the similarity law. Two groups of shaking table tests are conducted to simulate the behaviors of two types of landslide dams:one with small particle size having the cohesive materials(dam I) and the other with large particle size not having the cohesive materials(dam II). The shaking table tests were conducted under different earthquake waves, different peak ground accelerations(PGA) and different water depths. The following conclusions are drawn:(1) The model dams have stable X-directional and Z-directional natural frequency and damping ratio. (2) Earlier shaking makes the natural frequency to decrease and the damping ratio to increase. The natural frequency of dam I is smaller than that of Dam II. The effects of water depth on the natural frequency of the two types of dams are different. (3) In vertical direction,acceleration amplification factor increases from the base to the top of the dam. The maximum accelerations occurred mainly on the top of the dams. In horizontal direction,the maximum accelerations occurred on the upstream and downstream surfaces of dam slopes,i.e. the surface amplification effect,which showed that the dam slope surfaces were prone to fail under earthquake action. (4) The earthquake waves with the predominant frequency close to the natural frequency of landslide dams induce the most prominent acceleration response. The earthquake in Z direction made the amplification factor of acceleration in X direction increase. The acceleration amplification factor decreases as PGA increases.