| In this paper,selecting the small radius curve section in right line of the shield tunneling project from a city subway as an example,according to the geological conditions of the water-rich sand stratum and the features of the shield tunnel with small radius curve segment,the main research contents,including the adaptability of the shield machine selection,selection and correction of the key tunneling parameters of the shield machine,attitude control and deviation correction measures of the shield machine,are investigated and analyzed using field monitoring data.The main research contents and achieved conclusions are provided as follows:1.Analysis and investigation on the adaptability of shield machine selection.According to the main influencing factors such as formation permeability coefficient,water pressure and particle gradation,the most preferred type of the shield machine for the small radius curve segment shield construction in water-rich sand stratum is investigated.The main factors considered in the selection of shield machine cutter head system,shield body setting and auxiliary system parameters are analyzed.Furthermore,the selection basis of the shield machine turning ring segment parameters during the construction of small radius curve segment is further illustrated.Results show that when the river inrush water level is close to the groundwater level and there is a water-rich sand stratum closely related to the river inrush water and groundwater,the slurry balance shield machine is suggested to be selected,and the cutter head opening rate of the shield machine can be appropriately increased to achieve better engineering adaptability for the zone containing clay stratum.The fitting effect of the tunnel curve can be better achieved by determining the wedge of the turning ring.2.Key tunneling parameter selection and correlation investigations of the shield machine.The six key parameters of the slurry water balance shield machine for the shield construction with small radius curve segment in water-rich sand stratum,including the shield thrust,tunneling speed,cutter head torque,cutter head speed,penetration and grouting amount,are statistically analyzed.The correlations among the key tunneling parameters are further investigated.The suggestions for the selection of the key tunneling parameters are given.The specific torque and specific thrust of the slurry balance shield machine show relatively strong positive proportional linear relationship.The tunneling speed and specific thrust show relatively strong negative proportional linear relationship.3.Study on attitude control and deviation correction measures of the shield machine.Combined with the features of the small radius curve of subway and the setting standard of the shield machine articulation mechanism,the control conditions of the shield machine for the small radius curve segment in water-rich sand stratum are illustrated.The attitude control measures of the shield machine are studied from three aspects,including the main control measures of shield machine,the use of hinged jack,and the hinged pressure protection and sealing.Under the premise of maintaining pressure and sealing,the principles and methods for construction control based on the guidelines of scaling and contracting,diligent measurement,gradually correction,speed control,short stroke,and multi-cycle are suggested,which can adjust the attitude to be within stable state.On this basis,through theoretical analysis and case study on the attitude correction measures of shield machine,two criteria of the attitude deviation of the shield machine for the small radius curve segment shield construction and the function relationship between the correction trend of shield machine and the design axis are presented.The research content and results of this paper can provide reliable guidance for the selection of the tunneling parameters,and construction control of the slurry water balance shield machine for the small radius curve segment in water-rich sand stratum.The achievements show valuable reference and practical significance. |
