极地粒雪层融水旋喷成桩方法的可行性研究

Feasibility study on method of rotary jetting pile-formation in firn with melting water in polar regions

摘要:

钻穿极地冰盖，并获取冰下基岩样品对于揭示极地冰下地质环境具有重要意义。极地冰盖上部一般覆盖有高渗透性的粒雪层。使用高压空气或钻井液在粒雪层钻进时，如果不进行粒雪层的加固，则高压空气和钻井液就会渗漏进周围粒雪层，导致钻进作业无法继续开展。因此，在极地开展冰下基岩取心钻探的过程中，必须对粒雪层孔壁进行封隔加固。本文提出了一种利用融水旋喷成桩加固孔壁的方法，并对该方法进行了理论分析以及试验研究。研究结果表明，为了在粒雪层中得到0.4 m的融孔，注浆管的提升速度应为15~30 mm/min左右。当粒雪层厚度不超过100 m时，融水向下注入过程中的温度损失大致在16 ℃以下。一般条件下，成桩所需的水量不会超过16 m³。在极地寒冷环境下，在粒雪层通过融水旋喷再冻结的方法可以形成桩体。在-15 ℃的条件下，冻结成桩的时间约为60 h。

Abstract:

It is of great significance to drill across the polar ice sheet and obtain subglacial bedrock samples for revealing the geological environment beneath ice sheet. The upper part of the polar ice sheet is generally covered with highly permeable firn. When drill in the firn， the compressed air and drilling fluid would leak into the surrounding firn if it is not reinforced， resulting in the inability to continue drilling operations. Therefore， it is necessary to seal and reinforce the borehole wall of firn in the process of sampling subglacial bedrocks. In this paper， a method of rotary jetting pile formation with melting water is proposed， and the theoretical analysis and experimental study were carried out. The research results show that in order to obtain a 0.4m borehole in firn， the lifting speed of the grouting pipe should be about 15~30mm/min. When the firn thickness is less than 100m， the temperature loss of meltwater during downward injection is approximately below 16℃. In normal conditions， the amount of water required for pile formation does not exceed 16 m³. In the cold polar environment， piles can be formed in the firn through the method of meltwater rotary jetting and refreezing. At the temperature of -15℃， the time for freezing into piles is approximately 60h.