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黄土原要进行表层校正工作,是因为黄土原上存在较厚的低、降速层。马岭地区沟内表层结构是否也存在低、降速层呢?这是开始工作之前应该着手调查的问题。我们从环江主沟→野狐支沟→野2毛沟入手,发现从主沟→支沟→毛沟,表层结构是有所变化的。在支沟口外的河漫滩上,冲积层厚度加大,在支沟内部,次生黄土厚度较薄,甚至有青石板(环河组青灰色泥岩)出露,而至毛沟的沟脑处,上第三系红土厚度逐渐增大到好几十米。在记录上又发现野2及野3毛沟从沟口到沟脑的T_5标准层t_0值急剧增大(图1),
Loess correction of the surface to be the original work, because there is a thick loess original low velocity layer. Are there any low and slowdown layers in the ditch’s surface structure in Maling? This is the question that should be investigated before starting work. We start from the main channel of the river → wild fox furrows → wild 2 furrows and found that the surface structure is changed from the main furrow → branch furrow → furrow. On the floodplain outside of the ditch Mizoguchi, the alluvial layer thickness increases. In the branch ditch, the secondary loess is thinner in thickness, and even the bluestone plate (Qinghe mudstone) of the Huanhe Formation is exposed. However, The thickness of red clay on the Tertiary gradually increased to tens of meters. On the record, the value of t_0 in wild 2 and wild 3 furrows increased rapidly from Mizoguchi to ditch brain (Figure 1)