为研究超大直径盾构隧道联络通道冻结法施工中的交界面温度场，以及冻结管非循环段长度等因素对土体与管片交界面冻结壁厚度的影响，以北京东六环超大直径盾构隧道盾构段联络通道冻结施工为背景，采用现场实测和数值模拟的方法，对土体与管片交界面温度场及交界面冻结壁厚度等进行分析。结果表明： 1）冻结过程中冻结管前部的非循环段长度会显著影响交界面处的冻结效果，交界面冻结壁厚度随非循环段长度增加而减小； 在北京东六环工况下，冻结管间距为1 m时，非循环段长度达到450 mm冻结壁无法在56 d内闭合。2）单排管叠加冻结能显著提高交界面的冻结壁厚度及冻结管容许最大非循环段长度，而等管距的环形单圈冻结同直线单排管冻结无明显差距。3）冻结交界面为弧形时，交界面冻结壁厚度较管片为平面时有显著增加； 非循环段长度为300
mm时，上壁厚度比平面管片增加了15%，下壁和侧壁则增加了35%，可以认为管片弧度对交界面冻结有利。4）冻结壁与隧道管片交界面是冻结壁的薄弱位置，在冻结施工中应尽量减小非循环段长度，并重点关注交界面处的温度变化，积极冻结及开挖过程中应对交界面位置做好保温，防止施工过程中交界面位置化冻引起地下水击穿冻结壁，造成涌水涌砂事故。
The authors investigate the
interface temperature field during the freezing method used for the connecting
channel of a super-large diameter shield tunnel.
They also examine how the length of the non-circulating
section of the freezing pipe affects the thickness of the frozen wall at the
interface between the soil and segments. The research focuses on the freezing
construction of the connecting channel for the super-large
diameter shield tunnel on the East Sixth Ring Road of Beijing, employing both
field measurements and numerical simulations to analyze both the temperature
field and the thickness of the freezing wall at the soil-pipe segment interface. The results reveal the following: (1) The
length of the non-circulating section in front of the
freezing pipe significantly affects the freezing effect at the interface. As
this length increases, the thickness of the freezing wall at the interface
decreases. Under the working conditions of the Beijing East Sixth Ring Road, a
non-circulating section length of 450 mm with a
freezing pipe span of 1 m results in the inability to achieve a closed freezing
wall within 56 d. (2) The thickness of the freezing wall at the interface and
the maximum permissible length of the non-circulating
section are greatly enhanced through the superposition freezing of a single-row of tube. Notably, a circular single-ring
freezing configuration with an equivalent span yields similar results to that
of single-row of tube freezing. (3) The thickness of
the frozen wall at the interface significantly increases when the frozen
interface is curved, compared to when the segment is flat. For a non-circulating segment length of 300 mm, the upper wall thickness
increases by 15%, whereas the lower wall and sidewall each increase by 35%.
This indicates that segment curvature is beneficial for freezing at the
interface. (4) The interface between the frozen wall and tunnel segment
represents a weak point in the frozen wall structure. During the freezing
construction process, efforts should be made to minimize the length of the non-circulating section, and careful attention should be given to
temperature fluctuations at the interface. Active thermal insulation measures
should be implemented during freezing and excavation to prevent groundwater
from penetrating the frozen wall, thereby avoiding potential water and sand
gushing incidents due to defreezing at the interface during construction.
