深厚冲积层破损井筒修复过程中的控制冻结技术

Controlled freezing technology for repairing damaged shaft in deep alluvium

为了解决板集煤矿副井破损井筒修复过程中面临的突水问题,针对该井筒实际的破损情况以及所处地层的含水层分布规律,考虑到冻结壁在形成过程中将产生土体冻胀,从而对既有井筒产生较大的冻胀压力,为减少其对既有井筒的破坏作用,提出采用双圈孔控制冻结的方式对破损井筒的周边进行封水处理,即外圈孔采用全深(673 m)冻结,内圈孔只对破损、突水严重的380 m以深的地层进行局部冻结。为了实现对各个层位冻结壁厚度的有效控制以避免冻胀对既有井壁结构安全产生威胁,在冻结初期,根据冻结孔实际成孔情况和各个层位土体的热物理特性参数,以及冻结过程中测温孔实测数据,通过数值计算对各个层位的冻结壁的发展情况进行预测,并基于预测结果对部分冻结孔的冷量进行了控制。为了防止施工热扰动对冻结壁的稳定性造成不利影响,在井筒清理以及套壁施工过程中,根据温度场发展情况及时调整冷量供给。由现场实测数据可知,深度380 m以浅控制冻结地层的整体温度较深度380 m以深地层的温度高5℃左右,在整个修复施工过程中没有出现突水现象且冻结壁温度保持稳定。由此可见,控制冻结技术可有效限制土体冻胀,且冻结壁厚度较为均匀,封水性能较好,达到了预期的施工效果,该项施工技术可为今后类似工程的开展提供重要参考。

In order to solve the water inrush problem during the repair process of the damaged shaft of the auxiliary shaft in Banji coal mine,according to the actual damage of the shaft and the distribution law of aquifers in the stratum,and considering that the frozen wall would produce frost heaving during the formation process,in order to reduce the damage to the existing wellbore,it was proposed to use the control freezing technique with double-circle hole to seal the surrounding of the damaged wellbore.That is,the outer row of holes was frozen at full depth( 673 m),and the inner row of holes was partially frozen in severely damaged formation( 380 m and deeper).In order to effectively control the thickness of the frozen wall at each horizon to avoid the threat of frost heaving to the safety of the existing wellbore,according to the actual formation condition of frozen holes and the thermo-physical characteristics of the soil in each layer,during the freezing process,the measured data of the temperature measuring holes were used to predict the development of the frozen wall at various levels through numerical calculations,and the cooling capacity of some freezing holes was controlled based on the prediction results. In order to prevent the construction thermal disturbance from adversely affecting the stability of the frozen wall,in the process of wellbore cleaning and casting wall construction,the cooling supply was adjusted in time according to the development of the temperature field.It was known from the field test data that the overall temperature of the frozen formation above the depth of 380 m is about 5 ℃ higher than that of the stratum below the depth of 380 m.There is no water inrush phenomenon and the temperature of the frozen wall remained stable during the entire restoration process.It can be seen that the freezing control technology effectively limited the soil frost heaving,and the thickness of the frozen wall was relatively uniform,and the water sealing performance could meet design requirements,and the expected construction effect was achieved.This construction technology could provide an important reference for the development of similar projects in the future.