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一、问题的由来倒垂观测孔,是用来安装监测水工建筑物水平位移观测装置的,具有特殊要求的钻孔。它的垂直精度之高,难度之大,是一般钻探技术不易胜任的。以葛洲坝工程倒垂孔的施工实践而论,倒垂孔采用φ168毫米孔径终孔,无论钻孔深浅,其偏斜值不得超过50毫米,换句话说,若设计孔深为50米,钻孔偏斜率仅有千分之一,即0.057度(3.44分)。当钻孔更深时,要求偏斜率更小。因此,为了达到钻孔的精度要求,在施工过程中常常要付出很大的代价,采取各种措施纠偏,如调整钻机角度,回填钻孔,扩大钻孔口径等等。即使如此,有时尚达不到目的。
First, the origin of the problem Upside down observation hole, is used to monitor the horizontal structure of hydraulic structures to observe the installation, with special requirements of drilling. Its high vertical accuracy, the difficulty of the general drilling technology is not competent. In Gezhouba inverted inverted hole construction practice, the inverted hole using φ168 mm aperture end hole, regardless of the depth of the drill, the skew value of not more than 50 mm, in other words, if the design hole depth of 50 meters, drilling Skew rate of only one thousandth, that is 0.057 degrees (3.44 points). Smaller skew rates are required when drilled deeper. Therefore, in order to meet the requirements of drilling accuracy, it is often a great deal of expense in the construction process. Various measures are taken to correct the errors, such as adjusting the angle of the drilling rig, backfilling the borehole, expanding the borehole diameter, and the like. Even so, fashion can not achieve its purpose.