With the development of global urbanization,the utilization of underground space is more critical and attractive for civil purposes.Various shapes of shield tunnels have been gradually proposed to cope with different ...With the development of global urbanization,the utilization of underground space is more critical and attractive for civil purposes.Various shapes of shield tunnels have been gradually proposed to cope with different geological conditions and service purposes of underground structures.Generally,reducing the burial depth of shield tunnel is conducive to construction and cost saving.However,extremely small overburden depth cannot provide sufficient uplift resistance to maintain the stability and serviceability of the tunnel.To this end,this paper firstly reviewed the status of deriving the minimum sand over-burden depth of circular shield tunnel using mechanical equilibrium(ME)method.It revealed that the estimated depth is rather conservative.Then,the uplift resistance mechanism of both circular and rectangular tunnels was deduced theoretically and verified with the model tests.The theoretical uplift resistance is consistent with the experimental values,indicating the feasibility of the proposed equations.Furthermore,the determination of the minimum soil overburden depth of rectangular shield tunnel under various working conditions was presented through integrated ME method,which can provide more reasonable estimations of suggested tunnel burial depth for practical construction.Additionally,optimizations were made for calculating the uplift resistance,and the soil thickness providing uplift resistance is suggested to be adjusted according to the testing results.The results can provide reference for the design and construction of various shapes of shield tunnels in urban underground space exploitation.展开更多
In this paper, the influence depths of all levels of wind power produced waves are reckoned according to the measured swaying degree when a submarine meets with a force 11 strong tropical storm and has to submerge; Th...In this paper, the influence depths of all levels of wind power produced waves are reckoned according to the measured swaying degree when a submarine meets with a force 11 strong tropical storm and has to submerge; Then the minimum submergence depth is given when a submarine is faced with weather systems with force ≥ 6 wind and the swaying degree of less than 12 degree is assured as reference for a submarine working and sailing in big strong winds and waves.展开更多
Accurately predicting the overlying pressure is crucial for determining an appropriate cover depth of underwater box tunnels to avoid the uplifting failure.Based on the project of box jacking crossing the Beijing-Hang...Accurately predicting the overlying pressure is crucial for determining an appropriate cover depth of underwater box tunnels to avoid the uplifting failure.Based on the project of box jacking crossing the Beijing-Hangzhou Grand Canal in Suzhou,the characteristics of overlying pressure variation during tunneling are investigated.The monitoring results reveal that the fluctuation of overlying pressure is weakened during the rapid tunneling process.A modified analytical model for vertical earth pressure is conceived,in which the active and passive limit states for multi-layered soils are both considered.The probable range of overlying pressure obtained by the proposed model is suitable to cover the actual values.The anti-floating behavior of underwater box tunnels for two different working conditions is discussed by calculating the minimum cover depth.Using the calibrated analytical models,a parametric study is conducted to explore the influence of injection pressure,hardened slurry unit weight,soil internal friction angle,soil cohesion,and tunnel geometry.It is found that the injection pressure during the construction process is crucial for determining the necessary cover depth,and the change of box tunnel height makes it easier to trigger the variation of minimum cover depth.展开更多
基金support from National Major Scientific Instruments Development Project of China(Grant No.5202780029)Program of Distinguished Young Scholars,Natural Science Foundation of Chongqing,China(Grant No.cstc2020jcyjjq0087)Research on resilience prevention,control and adaptation strategy of flood disaster in megacities under changing environment(Grant No.2021-ZD-CQ-2).
文摘With the development of global urbanization,the utilization of underground space is more critical and attractive for civil purposes.Various shapes of shield tunnels have been gradually proposed to cope with different geological conditions and service purposes of underground structures.Generally,reducing the burial depth of shield tunnel is conducive to construction and cost saving.However,extremely small overburden depth cannot provide sufficient uplift resistance to maintain the stability and serviceability of the tunnel.To this end,this paper firstly reviewed the status of deriving the minimum sand over-burden depth of circular shield tunnel using mechanical equilibrium(ME)method.It revealed that the estimated depth is rather conservative.Then,the uplift resistance mechanism of both circular and rectangular tunnels was deduced theoretically and verified with the model tests.The theoretical uplift resistance is consistent with the experimental values,indicating the feasibility of the proposed equations.Furthermore,the determination of the minimum soil overburden depth of rectangular shield tunnel under various working conditions was presented through integrated ME method,which can provide more reasonable estimations of suggested tunnel burial depth for practical construction.Additionally,optimizations were made for calculating the uplift resistance,and the soil thickness providing uplift resistance is suggested to be adjusted according to the testing results.The results can provide reference for the design and construction of various shapes of shield tunnels in urban underground space exploitation.
文摘In this paper, the influence depths of all levels of wind power produced waves are reckoned according to the measured swaying degree when a submarine meets with a force 11 strong tropical storm and has to submerge; Then the minimum submergence depth is given when a submarine is faced with weather systems with force ≥ 6 wind and the swaying degree of less than 12 degree is assured as reference for a submarine working and sailing in big strong winds and waves.
基金supported by the Natural Science Foundation of Jiangsu Province of China (Grant Nos.BK20230500 and BK20210721)the Young Talent Fund of Association for Science and Technology in Shaanxi,China (Grant No.20240722).
文摘Accurately predicting the overlying pressure is crucial for determining an appropriate cover depth of underwater box tunnels to avoid the uplifting failure.Based on the project of box jacking crossing the Beijing-Hangzhou Grand Canal in Suzhou,the characteristics of overlying pressure variation during tunneling are investigated.The monitoring results reveal that the fluctuation of overlying pressure is weakened during the rapid tunneling process.A modified analytical model for vertical earth pressure is conceived,in which the active and passive limit states for multi-layered soils are both considered.The probable range of overlying pressure obtained by the proposed model is suitable to cover the actual values.The anti-floating behavior of underwater box tunnels for two different working conditions is discussed by calculating the minimum cover depth.Using the calibrated analytical models,a parametric study is conducted to explore the influence of injection pressure,hardened slurry unit weight,soil internal friction angle,soil cohesion,and tunnel geometry.It is found that the injection pressure during the construction process is crucial for determining the necessary cover depth,and the change of box tunnel height makes it easier to trigger the variation of minimum cover depth.
