Influence of alternating electric field on crystallization of tunnel drainage pipes-based on indoor orthogonal test

The blocking of tunnel drainage pipe caused by crystals from groundwater calcification is prone to bring about lining cracking and water leakage. In this paper, in order to prevent tunnel drainage pipes from the crystallization, this study proposed a method to prevent the binding of Yin and Yang ions based on the alternating electric field. For the purpose of concluding the crystallization rules of drainage pipes and verifying the feasibility of this method, an indoor orthogonal test was adopted to study the crystallization rules and anti-crystallization efficiency of three drainage pipes under three alternating electric fields at three voltages (6 V, 9 V, 12 V) and at three flows (34.7 ml/s, 76.9 ml/s and 192.0 ml/s). The results showed that: During the test, all the three voltages can reduce the crystallization of drainage pipes, and the anti-crystallization efficiency of all the three tested pipes was optimal at 6 V under each of three alternating electric fields, reaching 22%, 25%, 7%, respectively. Case 2 had the best anti-crystallization effect at 6 V. The reason is that, at 6 V, the crystals had the loosest and minimum grains and the largest interplanar spacing, so they were inclined to be discharged through the pipe under the water flow. At 34.7 ml/s, Case 2 had the best anti-crystallization effect at 12 V; At 76.9 ml/s and 192.0 ml/s, Case 2 had the best anti-crystallization effect at 6 V. The alternating electric field can prevent the tunnel drainage pipe from crystallization and blocking, and different drainage pipes in the alternating electric fields should be selected based on according to the groundwater in tunnel.