Research and Application of the Local Differential Freezing Technology in Deep Alluvium

Bin Wang,Chuanxin Rong,Haibing Cai,Hua Cheng,Zhishu Yao

doi:10.1155/2020/9381468

Bin Wang, Chuanxin Rong + Show 3 more

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https://doi.org/10.1155/2020/9381468

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Abstract

Aiming at the complicated engineering conditions of the auxiliary shaft repair in the Banji coal mine, it was proposed to seal the water around the shaft lining by differential control freezing technology using double rows of holes. The outer row of holes is completely frozen, and the inner row of holes is local differential frozen according to the degree of destruction of the shaft lining. The local differential freezing pipe was successfully developed according to engineering requirements. Numeral simulations were used to predict the development of the freezing temperature field; the results showed that the inward expansion range of the frozen wall formed by the inner row freezing holes was effectively limited and the temperature drop rate of the shaft lining was significantly reduced after the local differential freezing technique was adopted. The on-site monitoring data showed that the temperature of the limited freezing layer was about 5°C higher than that of the conventional freezing layer. During the drainage work and the construction of the new shaft lining, the thickness and average temperature of the frozen wall remained stable, indicating that the implementation of the local differential freezing technology achieved the expected results. Further analysis showed that when the temperature of the limited freezing part of freezing pipes in the inner row was controlled within the range of −15 to −10°C, not only could the frozen wall reach the design thickness and strength but the frost heaving pressure on the existing shaft lining could be effectively eliminated.

Highlights

Since 1987, more than 200 shafts have been damaged in Huang-Huai and Northeast China, severely threatening the safety of mine production and causing major economic losses
The repair of damaged shaft linings has become an important part of mine construction engineering [1,2,3,4,5]. e problem of water inrush has always been a major problem in the repair work of damaged shaft linings in water-rich areas. e artificial layer freezing method can form a frozen wall with a certain strength and good sealing performance by allowing constant heat exchange between the low-temperature refrigerant in the freezing pipes and the surrounding soil, which can provide a stable construction environment for the repair work of the shaft wall [6,7,8,9,10,11,12]
Erefore, to ensure that the frozen wall reached the design thickness as early as possible, and to ensure a certain safe distance between the frozen wall and the shaft lining, it is necessary to limit the temperature of the limited freezing part to a certain range, and the temperature range was determined to be from − 15 to − 10°C in this study

Summary

Introduction

Since 1987, more than 200 shafts have been damaged in Huang-Huai and Northeast China, severely threatening the safety of mine production and causing major economic losses. E problem of water inrush has always been a major problem in the repair work of damaged shaft linings in water-rich areas. E artificial layer freezing method can form a frozen wall with a certain strength and good sealing performance by allowing constant heat exchange between the low-temperature refrigerant in the freezing pipes and the surrounding soil, which can provide a stable construction environment for the repair work of the shaft wall [6,7,8,9,10,11,12]. Shi used low-temperature liquid nitrogen to reinforce and freeze the partially unfrozen area, which solved the problem of brine being unable to form a closed frozen wall under complex formation conditions [14].

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