Researches On Behavioral Characteristics Of Traffic Engineering Slopes Under Seismic Actions

Researches on behavioral characteristics of traffic engineering slopes under seismic actions have been the hot issue in recent years. With the investment in national engineering construction, large numbers of line projects in China will inevitably run through seismically active areas, as a result, scientific researchers will face lots of complicated slope problems, and slope problems will stand out increasingly along with the proceeding of engineering construction. In this paper, theoretical researches on dynamics of slope engineering geological problems were performed by laboratory physical model tests, numerical simulation algorithm and other methods based on comprehensive research on various slope failure modes of modern transport line projects, thus providing theoretical dynamic basis for control and protection of traffic engineering slopes as well as prediction and evaluation of geological hazards of traffic engineering slopes. Major research achievements are as follows:(1) A2D one-way vibration test bench is designed according to mechanical design principles and structural dynamic principles. The displacement-time curve of a model box is acquired using a displacement sensor and a dynamic acquisition system, and the displacement-time curve in one-way vibration under ideal conditions is acquired by theoretical calculation of structural dynamics, and comparison between the two curves shows that the vibration test bench has stable overall performance and can meet vibration tests of small loads.(2) Slope forms have direct impact on deformation and failure of slopes; for convex slopes, overall deformation and failure can occur instantaneously in case of application of vibration force due to large sliding masses, for concave slopes, segmental sliding of sliding masses easily occurs under the action of vibration force due to small sliding masses, masses below sliding masses slide, resulting in overall sliding failure of the sliding masses, the resulting macro phenomena are that surface fissure occurs earlier than top fissure for concave slopes, on the contrary, top fissure occurs earlier than surface fissure for convex slopes. Deformation and failure of combined concave and convex slopes are impacted by projections of slopes.(3) Deformation and failure of slopes and dip angles of sliding surfaces are directly related to concave and convex extent of slope surfaces; the stronger the concave or convex extent of the slope is, the less the remaining slope crest is after vibration tests; and analysis reveals that dip angles of sliding beds of sliding surfaces increase gradually with the decline of the concave or convex extent of the slope surfaces.(4) Slope forms have direct impact on the distribution of slope acceleration; the maximum slope acceleration amplification coefficient appears at local concave and convex slope areas, and gradually decreases outwards, under the same circumstances, the acceleration magnification effects of convex slopes are stronger than the amplification effects of concave slopes. With regard to combined concave and convex slopes, the maximum acceleration magnification effects occur at depression and projection of slopes. Acceleration tends to increase with the increase of slope height with regard to the same slope, and the amplification effects of slopes at the same height are larger than those in slopes, however, internal acceleration distribution of slopes of different slope forms is the same, indicating that slope forms have small impact on internal acceleration distribution of slopes.(5) Physical model tests on stratified rock slopes reveal that deformation and failure of bedding model slopes are mainly sliding failure along fixed bedding surfaces, and deformation and failure of anti-dip model slopes are mainly failure of avalanche masses.(6) Tunnel portals at higher elevation are prone to overall failure as they are included in sliding masses, and tunnel portals at lower elevation are easily blocked due to slump accumulation.(7) Parameters of structural planes have great impact on dynamic response of slopes; lower slopes of slopes with small structural plane stiffness have smaller peak values of the three factors, and upper slopes have larger peak values of the three factors; the closer the structural planes is to the slope crest, the larger the amplification coefficient of the three factors of upper slopes of the structural planes is; with the increase of dip angles of structural planes, the slope acceleration amplification coefficient of bedding structural planes increases, and the slope acceleration amplification coefficient of anti-dip structural planes decreases, the slope acceleration amplification coefficient of bedding structural planes is integrally larger than the slope acceleration amplification coefficient of anti-dip structural planes. Slopes with smaller structural plane thickness have stronger dynamic response, and slopes with larger structural plane thickness have weaker dynamic response; slopes with different connectivity rates of structural planes have obvious differences in acceleration peak values, and structural planes with larger connectivity rates have stronger amplification effects at structural planes. (8) By summarizing the analysis on seismic safety of the slope project at Taiping Tunnel portal, the slope at Taiping Tunnel portal is greatly impacted by structural planes, in an earthquake, cutting blocks of structural planes will slide in overall and individual blocks under the action of tensile stress and shear stress. However, as the tunnel portal is located in a moderate position, sliding surfaces of sliding masses are above the tunnel portal, and the portal will not be blocked by the sliding masses, this pattern provides good prerequisite conditions for quick traffic operation after earthquake of slopes at tunnel portals. Generally speaking, the slope site of Taiping Tunnel portal is appreciable.