Study On Key Construction Technologies Of The New Monolayer Freezing Shaft Lining In Deep Water-rich Bed Rock

In deep water-rich bedrock in West China, how should we do to prevent pore water pressurefrom separating shaft lining from surrounding rock when frozen wall thawing, how to avoid totalhydrostatic pressure on whole outer surf_ace of the shaft lining, what measures should we take toprevent leaking cracks in shaft lining in advance and deal with them through grouting technologyafterwards, the key technologies to solve these problems have become an urgent task in theconstruction of the new monolayer freezing shaft lining.In this paper, the variation of the radial interaction force f_acaused by shaft lining excavationis firstly discussed through numerical analysis. The results show that:1) f_acan be represented asa function of shaft depth H (f_a=K_fH);2) The common value of radial unloading rate η of frozenwall inner edge is0.403~0.911.Based on axisymmetrical plane strain model, stress and displacement analytical solution ofthe new monolayer freezing shaft lining during freeze sinking are obtained through stressanalysis. In addition, after analyzing the variation of total radial interaction forcef_x, thetechnical measures are also promoted to avoid the tensile stress between shaft lining and bedrockwhen frozen wall thawing.Aiming at the three probable leaking channels of the new monolayer freezing shaft lining,firstly, the generation mechanism of shaft lining cracks during shaft sinking is described. Then,through numerical analysis and field measurement, the key construction technologies used innew monolayer freezing shaft lining in the bedrock are discussed detailedly. The research resultsshow that:1) When the distance between freezing pipes and sidewall D_f≥3m and sidewalltemperature t_b≥-5℃, the positive temperature curing time of shaft lining can be ensured to begreater than or equal to26.7d;2) When the gradually stabilized concrete expansion strain tisnot less than300μ and the28-day expansion strain is not less than50%(i.e.150μ), thetangential and vertical temperature cracks in shaft lining can be avoided;3) Verticalreinforcement preload can take the value of20kN, and the pre-tightening process should becompleted before concrete is poured to half of construction segment height;4) Radial interactionforce f_aplays a significant role in controling temperature tensile stress of the shaft lining;5)"Top-down concentrated grouting process" is suggested for new-old concrete interf_acegrouting. The grouting pressure should be taken as1times the hydrostatic pressure;6) If thenew-old concrete interf_ace do not leaking for about3minute and grouting pressure do notdecrease, then the effect of grouting can be thought good.Based on the project example of Hulusu auxiliary shaft of Hujierte coal mine in Erdos, theconstruction technology and monitoring method of the first new single-layer shaft lining are described in bed rock during freeze sinking in China. The In-situ monitoring results show that:1) The freezing pressure is mainly affected by rock moisture content and rock strength, but therocks buried deep H affects little;2) The measured value of Pmaxis1.08~1.74MPa. Pmaxis muchsmaller than hydrostatic pressure P0and the maximum freezing pressure Pωin deep alluvium;3) The maximum stress of vertical steels is less than70.8MPa and the maximum stress of hoopsteels is less than101.0MPa. The maximum stress is only equal to about1/3of the strengthdesign value300MPa of reinforcement HRB335.4) Among the in-situ measurement stratumsF1~F3, the extreme compressive strain is just only25.7%,19.2%and19.0%of the concreteultimate compressive strainmax.5) In conclusion, the new single-layer shaft lining of Hulusuauxiliary shaft is in safe status during shaft freezing sinking.Finally, the key construction technologies are summarized for the new monolayer freezingshaft lining in bedrock. The research results can provide a reference for field technicians andhave important reference value for follow-up application of the new monolayer shaft lining.