In the framework of upper bound theorem of limit analysis, the progressive collapse of shallow rectangular tunnels with double-layer rock mass has been theoretically analyzed based on the three-dimensional (3D) veloci...In the framework of upper bound theorem of limit analysis, the progressive collapse of shallow rectangular tunnels with double-layer rock mass has been theoretically analyzed based on the three-dimensional (3D) velocity discontinuity surfaces. According to the virtual work principle, the difference theorem and the variation method, the collapse surface of double-layer rock mass is determined based on the Hoek-Brown failure criterion. The formula can be degenerated to a single-layer rock collapsing problem when the rock mass is homogeneous. To estimate the validity of the result, the numerical simulation software PLAXIS 3D is used to simulate the collapse of shallow tunnels with double-layer rock mass, and the comparative analysis shows that numerical results are in good agreement with upper-bound solutions. According to the results of parametric analysis, the potential range of collapse of a double-layer rock mass above a shallow cavity decreases with a decrease in A1/A2,σci1/σci2 and σtm1/σtm2 and an increase in B1/B2,γ1/γ2. The range will decrease with a decrease in support pressure q and increase with a decrease in surface overload σs. Therefore, reinforced supporting is beneficial to improve the stability of the cavity during actual construction.展开更多
In large-diameter shield tunnels,applying the double-layer lining structure can improve the load-bearing properties and maintain the stability of segmental lining.The secondary lining thickness is a key parameter in t...In large-diameter shield tunnels,applying the double-layer lining structure can improve the load-bearing properties and maintain the stability of segmental lining.The secondary lining thickness is a key parameter in the design of a double lining structure,which is worth being explored.Based on an actual large-diameter shield tunnel,loading model tests are carried out to investigate the effect of the secondary lining thickness on the mechanical behaviours of the double lining structure.The test results show that within the range of secondary lining thicknesses discussed,the load-bearing limit of the double-layer lining increases with growing secondary lining thickness.As a passive support,the secondary lining acts as an auxiliary load-bearing structure by contacting the segment.And changes in secondary lining thickness have a significant effect on the contact state between the segment and secondary lining,with both the contact pressure level and the contact area between the two varying.For double-layer lining structures in large-diameter shield tunnels,it is proposed that the stiffness of the secondary lining needs to be matched to the stiffness of the segment,as this allows them to have a coordinated deformation and a good joint load-bearing effect.展开更多
As a kind of transportation mode for crossing channels, undersea tunnel has incomparable advantages for its directness, convenience, fastness, insusceptibility to weather conditions, and smaller influences on environm...As a kind of transportation mode for crossing channels, undersea tunnel has incomparable advantages for its directness, convenience, fastness, insusceptibility to weather conditions, and smaller influences on environments. In recent years, with the development of undersea tunnel construction, the design and construction technologies have been greatly enhanced. The first undersea tunnel in China has just been built. Waterproofing is the key technique of undersea tunneling. A new concept of waterproofing scheme of grouting, sealing, draining and divided sections was adopted in the construction of the tunnel based on the researches, the in-situ geological features, the astuteness of the current technology and the cost of construction. The structural details of the sealing and draining system are introduced to illustrate the salient features of the new waterproofing technique. It is hoped that experiences described in the paper can offer guidance for the construction of the extensive undersea tunnels in the coming years.展开更多
海底隧道平纵线形组合方式复杂多样,容易导致驾驶人产生分心、疲劳等不良反应。为此,采集了30名驾驶人的实车数据,量化分析了海底隧道平纵线形对驾驶人视觉特征及车速的影响。运用Facelab眼动仪、GPS X10车载坡度计、行车记录仪等设备...海底隧道平纵线形组合方式复杂多样,容易导致驾驶人产生分心、疲劳等不良反应。为此,采集了30名驾驶人的实车数据,量化分析了海底隧道平纵线形对驾驶人视觉特征及车速的影响。运用Facelab眼动仪、GPS X10车载坡度计、行车记录仪等设备采集眨眼频率、单位时间内人眼闭合时间所占比例(percentage of eye closure over the pupil per unit time,PERCLOS)、隧道坡度、车速等数据。利用偏相关性分析得出海底隧道坡度、曲率与驾驶人眨眼频率、PERCLOS、车速的相关性及显著性,采用Ploy 2D非线性曲面拟合方法,分别建立眨眼频率、PERCLOS、车速与坡度-曲率的数学模型,量化分析眨眼频率、PERCLOS及车速与海底隧道平纵线形之间的关系,进而反映出海底隧道不同平纵线形组合对驾驶人的精神状态及行车状态的影响。结果表明:坡度1.3%和圆曲线半径4348 m的海底隧道平纵线形组合方式下,驾驶人的眨眼频率最大,精神最放松,适当增加上坡坡度值、减小圆曲线半径可以提高驾驶人的紧张感;坡度3.05%和圆曲线半径3521 m的海底隧道平纵线形组合方式下,驾驶人的PERCLOS最大,疲劳程度最高,适当增加下坡坡度值、减小圆曲线半径可以缓解驾驶人的疲劳;坡度1.78%和圆曲线半径2433 m的海底隧道平纵线形组合方式下,车速最快,适当增加上坡坡度值和圆曲线半径,可以降低车速。本文构建的视觉特征及车速模型,可以反映驾驶人的精神及行车状态随平纵线形的变化,为海底隧道平纵线形安全设计与运营管理提供理论支撑。展开更多
基金Projects(51478477,51878074)supported by the National Natural Science Foundation of ChinaProject(2017-123-033)supported by the Guizhou Provincial Department of Transportation Foundation,ChinaProjects(2018zzts663,2018zzts656)supported by the Fundamental Research Funds for the Central Universities,China
文摘In the framework of upper bound theorem of limit analysis, the progressive collapse of shallow rectangular tunnels with double-layer rock mass has been theoretically analyzed based on the three-dimensional (3D) velocity discontinuity surfaces. According to the virtual work principle, the difference theorem and the variation method, the collapse surface of double-layer rock mass is determined based on the Hoek-Brown failure criterion. The formula can be degenerated to a single-layer rock collapsing problem when the rock mass is homogeneous. To estimate the validity of the result, the numerical simulation software PLAXIS 3D is used to simulate the collapse of shallow tunnels with double-layer rock mass, and the comparative analysis shows that numerical results are in good agreement with upper-bound solutions. According to the results of parametric analysis, the potential range of collapse of a double-layer rock mass above a shallow cavity decreases with a decrease in A1/A2,σci1/σci2 and σtm1/σtm2 and an increase in B1/B2,γ1/γ2. The range will decrease with a decrease in support pressure q and increase with a decrease in surface overload σs. Therefore, reinforced supporting is beneficial to improve the stability of the cavity during actual construction.
基金supported by the National Natural Science Foundation of China(Grant Nos.52178398,51991394,and 51278424).
文摘In large-diameter shield tunnels,applying the double-layer lining structure can improve the load-bearing properties and maintain the stability of segmental lining.The secondary lining thickness is a key parameter in the design of a double lining structure,which is worth being explored.Based on an actual large-diameter shield tunnel,loading model tests are carried out to investigate the effect of the secondary lining thickness on the mechanical behaviours of the double lining structure.The test results show that within the range of secondary lining thicknesses discussed,the load-bearing limit of the double-layer lining increases with growing secondary lining thickness.As a passive support,the secondary lining acts as an auxiliary load-bearing structure by contacting the segment.And changes in secondary lining thickness have a significant effect on the contact state between the segment and secondary lining,with both the contact pressure level and the contact area between the two varying.For double-layer lining structures in large-diameter shield tunnels,it is proposed that the stiffness of the secondary lining needs to be matched to the stiffness of the segment,as this allows them to have a coordinated deformation and a good joint load-bearing effect.
基金supported by the National Basic Research Program of China (973 Program,Grant No. 2010CB732104)the Fundamental Research Funds for the Central Universities (Grant No. 2011JBM133)
文摘As a kind of transportation mode for crossing channels, undersea tunnel has incomparable advantages for its directness, convenience, fastness, insusceptibility to weather conditions, and smaller influences on environments. In recent years, with the development of undersea tunnel construction, the design and construction technologies have been greatly enhanced. The first undersea tunnel in China has just been built. Waterproofing is the key technique of undersea tunneling. A new concept of waterproofing scheme of grouting, sealing, draining and divided sections was adopted in the construction of the tunnel based on the researches, the in-situ geological features, the astuteness of the current technology and the cost of construction. The structural details of the sealing and draining system are introduced to illustrate the salient features of the new waterproofing technique. It is hoped that experiences described in the paper can offer guidance for the construction of the extensive undersea tunnels in the coming years.
文摘海底隧道平纵线形组合方式复杂多样,容易导致驾驶人产生分心、疲劳等不良反应。为此,采集了30名驾驶人的实车数据,量化分析了海底隧道平纵线形对驾驶人视觉特征及车速的影响。运用Facelab眼动仪、GPS X10车载坡度计、行车记录仪等设备采集眨眼频率、单位时间内人眼闭合时间所占比例(percentage of eye closure over the pupil per unit time,PERCLOS)、隧道坡度、车速等数据。利用偏相关性分析得出海底隧道坡度、曲率与驾驶人眨眼频率、PERCLOS、车速的相关性及显著性,采用Ploy 2D非线性曲面拟合方法,分别建立眨眼频率、PERCLOS、车速与坡度-曲率的数学模型,量化分析眨眼频率、PERCLOS及车速与海底隧道平纵线形之间的关系,进而反映出海底隧道不同平纵线形组合对驾驶人的精神状态及行车状态的影响。结果表明:坡度1.3%和圆曲线半径4348 m的海底隧道平纵线形组合方式下,驾驶人的眨眼频率最大,精神最放松,适当增加上坡坡度值、减小圆曲线半径可以提高驾驶人的紧张感;坡度3.05%和圆曲线半径3521 m的海底隧道平纵线形组合方式下,驾驶人的PERCLOS最大,疲劳程度最高,适当增加下坡坡度值、减小圆曲线半径可以缓解驾驶人的疲劳;坡度1.78%和圆曲线半径2433 m的海底隧道平纵线形组合方式下,车速最快,适当增加上坡坡度值和圆曲线半径,可以降低车速。本文构建的视觉特征及车速模型,可以反映驾驶人的精神及行车状态随平纵线形的变化,为海底隧道平纵线形安全设计与运营管理提供理论支撑。
