富水砂层交叠联络通道冻结设计方案研究

Freezing Method Design for Overlapping-Connecting Galleries in Water-Rich Sandy Stratum

与常规联络通道冻结相比,交叠联络通道的冻结体量大、开挖构筑时间长、冻结孔布置形式更加复杂,其冻结设计与常规冻结设计有明显差异。为实现富水砂层叠落区间联络通道安全高效施工,结合叠落区间交叠联络通道结构形式,进行异型联络通道冻结方案设计。首先,在哈尔滨地铁3号线2期河松街站工程现场取土,并送至冻土实验室进行土体低温物理力学试验,得到-10℃时低温土体物理力学参数,确定粉质黏土-10℃环境下单轴抗压强度为3.53 MPa;根据试验结果进行冻结壁厚度设计,得到通道顶部及侧墙冻结壁厚度为3.0 m,集水井底部冻结壁厚度为4.0 m,平均温度为-10℃。数值计算结果表明,冻结壁强度和位移指标均满足安全要求。根据冻结壁厚度布置冻结孔,提出“地面垂直+洞内水平冻结”加固方式。针对距离建筑物较近的特点,为控制冻胀,采用地面垂直泄压孔与洞内水平泄压孔相结合的方式,施工期间地表最大冻胀量为8.59 mm,对环境影响可控。工程实践表明,采用该设计方案开挖工作面稳定性好,冻胀量可控。

Compared to conventional-connecting galleries,overlapping-connecting galleries present unique challenges.These include larger frozen volumes,longer excavation and construction times,and more complex freezing hole layouts.To safely and efficiently construct overlapping-connecting galleries in water-rich sandy strata,a freezing scheme is designed based on their structural forms.First,soil samples are collected from the Hesongjie station site of phase Ⅱ of the Harbin metro line 3.Physico-mechanical tests are then conducted at the temperature of-10℃.The results reveal a uniaxial compressive strength of 3.53 MPa for silty clay.Then,the thickness of the frozen walls at an average temperature of-10℃is determined.The top and sidewalls are found to be 3.0 m thick,while the collecting well is estimated to be 4.0 m thick.Numerical calculation results illustrate that both the strength and displacement indicators of the frozen walls meet the safety requirements.Moreover,freezing holes are arranged according to the thickness of the frozen walls.A reinforcement method of"vertical freezing on ground and horizontal freezing in the tunnel"is also proposed.The implementation of pressure-relief holes on the ground and horizontal pressure-relief holes in the tunnel effectively control frost heave,limiting it to a maximum of 8.59 mm.This reduces the impact on the surrounding environment.In conclusion,the proposed method ensures the stability of the excavation face and controls frost heave within the allowable range.