前言为了观测万安大坝水平位移和沉陷情况,我队承包了大坝外部变形观测钻探造孔任务。钻孔地层是中细粒砂岩、粉砂岩、砾岩及第四纪覆盖层(土层、砂卵石层)。可钻性4—7级。要求进入微新基岩2米终孔。孔斜要求终孔不超过0.5度。孔径168毫米,一径到底。共完成十个钻孔,总进尺 Foreword In order to observe the horizontal displacement and subsidence of Wanan Dam, our team contracted the external deformation observation and drilling of the dam to create the hole task. Drilled formations are medium-fine sandstone, siltstone, conglomerate and Quaternary overburden (soil layer, sand and gravel layer). Drilling ability 4-7 level. Requires access to micro-new bedrock 2 meters final hole. Hole oblique hole requirements of not more than 0.5 degrees. Aperture 168 mm, a diameter in the end. A total of 10 completed drilling, the total footage