Seismic Response Analysis Of Coal Mine Shaft Tower Based On Soil-Wellbore-Shaft Tower

The seismic response of coal mine shaft tower under soil-wellbore-shaft tower interaction is obviously different from the due response presented by only the seismic response of shaft tower taken into consideration.However,when the structure of the shaft tower is designed,it is traditionally presupposed that the shaft tower is built on the rigid foundation,with the soil-wellbore-shaft tower interaction force on the seismic response of the shaft tower neglected.Based on the current engineering background,the influence of soil-wellbore-shaft tower interaction on seismic response analysis of inverted cone foundation shaft tower and piled raft foundation shaft tower was studied under different site conditions systematically.Taking the interaction force into considerations is the key to the rational seismic design of both inverted cone foundation shaft tower and piled raft foundation shaft tower.It is also of great significance in improving the seismic safety of new shaft towers.The main research work,the specific findings and major conclusions are summarized as follows.1)The experiment adopted Winkler foundation beam model and Penzien centralized mass model.By means of theoretical analysis and numerical analysis,it was systematically studied in site Ⅱ and site Ⅲ,the influence of soil-wellbore-shaft tower interaction on seismic response analysis of inverted cone foundation shaft tower.In this way,the study fills the gap and improves the research in this field to some extent.The results showed that the enhancement coefficients of seismic action of inverted cone foundation shaft tower in site Ⅱ and site Ⅲ(tower acceleration)were 1.8 and 2.4respectively.That is,the shaking degree of shaft tower is amplified because of the interaction of soil-wellbore-shaft tower,which may affect the normal use of the equipment and the comfort of personnel,or cause the damage and collapse of shaft tower structure,which directly threatens the safety of life and property.2)With the soil-wellbore-shaft tower interaction taken into consideration,the theoretical analysis simplified model and theoretical motion equation in the time domain of the piled raft foundation shaft tower system were proposed and established.The influence of different foundation and its basic forms,different site conditions and different seismic waves on the seismic response analysis of shaft tower were systematically studied.It fills the research gap of the influence of soil-wellbore-shaft tower interaction on the seismic response analysis of shaft tower of pile raft foundation,and provides theoretical basis and support for relevant research.Among them,the adoption of non-fixed theoretical analysis simplified model and theoretical motion equation on the wellbore and the piled raft foundation shaft tower provides new ideas and methods for related researches.3)Compared with the rigid foundation shaft tower,the enhancement coefficients of seismic response of piled raft foundation fixed shaft tower and piled raft foundation nonfixed shaft tower was basically the same.The average values of the enhancement coefficients of interlayer displacement in site Ⅱ、Ⅲ and Ⅳ were in the range of 1.30-1.61,0.88-1.25 and 0.73-0.97,respectively.The average values of the enhancement coefficients of tower displacement in site Ⅱ、Ⅲ and Ⅳ were 1.27～1.41,0.86～0.94 and0.72～0.80 respectively.The average values of the enhancement coefficients of tower acceleration in site Ⅱ、Ⅲ and Ⅳ were mainly in the range of 1.70～1.95,1.20～1.71 and1.00～1.40 respectively.The increase of the enhancement coefficients of interlayer displacement,tower displacement and tower acceleration reflects the increase of the internal force,deformation and shaking degree of the shaft tower during earthquake.Small increase of enhancement coefficient can impact the normal functions of the shaft tower and equipment.However,a very big increase of enhancement coefficient will threaten the safety of the shaft tower.4)In site Ⅲ,with soil-wellbore-shaft tower interaction taken into consideration,the influence of the number of piles(12,22,44,66 and 88)on the seismic response of the shaft tower of piled raft foundation fixed shaft tower system and piled raft foundation non-fixed shaft tower system were studied.It is found that the seismic responses of the shaft tower of the two systems increase with the increase of pile number.The seismic response of the shaft tower of piled raft foundation shaft tower system with 88 piles was about 7%～13% larger than the system with 12 piles.The maximum absolute values of the differences between the two systems of interlayer displacement and tower acceleration were less than 5%,which proved that the results have little to do with the two connection forms.This argument has great theoretical and practical significance.Based on the above analysis,it is suggested that attention should be paid to the influence of soil-wellbore-shaft tower interaction on the seismic response analysis of coal mine shaft tower in project’s earthquake resistant design and seismic response analysis of inverted cone foundation shaft tower and piled raft foundation shaft tower.Figure 56;Table 109;Reference 131...