深部冻结井筒内壁早期温度-应力场演化特征研究

Research on evolution characteristics of early-age temperature-stress field of inner lining at deep frozen shaft

为了研究深部热-力耦合条件下冻结井筒内壁早期温度应力问题,基于固体热传导原理与轴对称热应力理论,提出了考虑如内热源、外部冷源、塑料板摩擦约束、上覆井壁荷载和地层侧压力等多种边界条件的深井内壁大体积混凝土热-力耦合方法。获得了深部冻结井筒内壁早期温度-应力场演化特征,确定了易出现早期温度裂缝的高风险区,提出了混凝土早期温度裂缝防治措施优化方向。结果表明:①应用热-力耦合数值模拟方法求解出内壁大体积混凝土温度、应变最大值与现场实测结果较一致;②由于内壁水化放热导致内壁浇筑后中心位置的温度远高于内、外缘附近区域,极易导致温度裂缝的出现;③内壁浇筑初期,内壁各个位置应变为正,呈内缘至中部大于外缘的规律;浇筑后期,内壁外缘至中心区域出现收缩变形,应变最大为-6×10-5;④内壁浇筑初期,内壁内部储存了一定的压应力,分布规律为内壁中部压应力大于内、外缘。随着内壁温度的不断下降,内壁外缘拉应力达到2.2 MPa,极易在此区域内出现井壁早期温度裂缝。

In order to study scientific problem of early thermal stress of inner lining at deep frozen shaft under thermo-mechanical coupling,the thermo-mechanical coupling numerical simulation method with many boundary conditions such as internal heat,external cold source,friction constraints,upward shaft load and formation lateral pressure were proposed based on heat conduction and axial symmetry thermal stress theory.The evolution characteristics of temperature-stress field was obtained.The high-risk area of early-age thermal cracking was identified.The optimized direction of many measures of reducing early-age thermal cracking were proposed.The results as follows:①the results of temperature and strain of inner lining by numerical model are consistent with field measurement.②Temperature in the center of inner lining is far higher than inner and outer edge due to the hydration exothermic and this easy to cause temperature crack⁃ing.③The strain value of inner lining is positive at early period of concrete poured,and center to inner edge value is higher than outer edge.Shrinkage strain emerged from center to outer edge and its value is-6×10-5 at the later period.④Pressure stress is stored in the inner lining at early period of concrete poured,and center value is higher than inner and outer edge.The tensile stress of inner lining at out⁃er edge is 2.2 MPa with temperature decline.