黄土覆盖土、岩接触地层中隧道围岩变形特征及支护技术研究
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摘要
土、岩接触带是越岭隧道常出现的一种围岩条件。如已建神延铁路羊马河隧道,甘肃陇西新松树湾隧道,山西离军高速公路以及宝天高速公路隧道等都遇到了这种地层。土、岩接触带中由于结构面的存在,不仅使得隧道围岩力学性质发生显著变化,而且也导致水文地质条件发生改变。当隧道开挖穿越这种特殊地层时往往引起围岩变形过大或塌方问题,这就促使人们对土、岩接触带中隧道成洞时围岩的变形特征和稳定性应开展深入研究。
本文结合宝天高速公路黑岭段隧道工程,首先通过室内试验研究了黄土、砂岩以及土、岩接触面物理指标和力学性质；其次,通过建立土、岩接触带隧道计算模型,定量分析了隧道围岩变形规律和衬砌结构内力变化特征；再次,通过建立隧道开挖初期支护锁脚锚管的数值模型,分析了钢拱架锁脚作用机理和锁脚锚管的合理长度和打入角度；最后,通过土压力系数和围岩变形内表比探讨了隧道埋置的临界深度。主要得出以下成果：
1)土、岩接触面是一个软弱结构面,其抗剪强度主要取决于软弱黄土的强度特性。随着土、岩接触面处上覆黄土含水量的增加,接触面的粘聚力显著减小；摩擦角亦减小,且小于黄土的摩擦角。
2)土、岩接触带隧道围岩的变形主要表现为围岩沉降位移较大,不均匀沉降较明显；最大沉降位移位置一般在土、岩接触面土体侧。这种围岩变形导致隧道衬砌结构内力变化较大,主要表现为衬砌结构轴力和弯矩一般在土、岩接触面岩体侧较大。
3)提出了用土、岩接触面的倾角、面积比、刚度比和埋深来定量描述土、岩接触带的方法；分析了倾角、面积比、刚度比、埋深以及开挖方式对土、岩接触带隧道围岩变形规律和衬砌结构内力变化特征的影响。表明影响最大为埋深和开挖方式,其次是面积比、倾角和刚度比。
4)锚管的长度和角度对支护结构的内力均有较大的影响,适宜的长度和角度不仅有利于限制围岩的变形,而且有利于发挥支护结构的内力一般的土质隧道锁脚锚管宜取3.0m。锁脚锚管的打入角度宜取30°。
5)用土压力系数界定深、浅埋临界深度约为洞径的2倍；用围岩变形内表比界定深、浅埋临界深度为洞径的1.7～3.0倍。
6)在土、岩接触带中开挖隧道时,应适当加强洞周边土体侧的支护,尤其在土体侧拱肩处应加强支护,从而保证支护结构的变形统一均匀；应进行合理地布局分步开挖,减小对土层的扰动。提出了开挖方式和支护方案选取的原则,即“防止扰动,土为重点；土侧强支,拱肩加强”。
The strata including soil and rock often appear in mountain of loess zone which often covers with four Era. When the tunnel passes through the loess mountain, there are the shallow-buried broken wall rock with soil-rock interface, Such as Shenyan railway Yangma river tunnel, Xinsongshuwan tunnel in Longxi county of Gansu province and Lijun speedway tunnel in Shanxi and Baotian speedway heiling tunnel and so on. This kind of geological strata not only affacts the mechanical properties of tunnel evidently, but also hydro-geological conditions taking place change significantly, which resultes in the water content significantly increasing on the interface. Because the complex stratum with soil-rock interface doesn't arouse a wide range of people's attention, a number of incidents include landslides, and too large rock deformation occure in the past practice. It also prompts to study the necessity and urgency of the soil and rock contacted stratum tunnel wall rock.
Firstly, this paper studies physical index and mechanics index of loess, standstone and soil and rock's interface-by indoor test; Secondly,establishing a describe mean of soil and rock contected stratum, and qualitative and quantification evaluating the deformation of soil and rock marched with stratum tunnel wall rock and the internal force changing features of lining structure by numerical simulation; Thirdly,creating a numerical analysis mean of the locked anchor tube, anaslysing mechanism of action of steel rib locked feet and determining the rational length and infiltrate angle of the locked anchor tube; Finally,determining deep or shallow burial critical depth by coefficient of earth pressure and inter and outer ratio of wall rock deformation.Enduce mostly conclusion as follows:
1) The soil and rock interface forms shear failure surface easily. The shear strength of interface depends mainly on the strength characteristics of weak loess. With the loess water content increasing on the soil and rock interface, cohesive strength on the interface decreases significantly; Angle of friction attenuate little,but smaller than loess's.
2) The deformation features of soil and rock contected stratum tunnel wall rock manifest mainly on wall rock settlement displacement too big and settlement not equality.The maximum settlement displacement is not in the biggest dome and is in the dome away from the soil tend to the location of about 30°. This differential settlement caused internal forces changes large in the structure of the tunnel lining,it manifests mainly that lining structure axial force and bending moment are larger near the rock in the soil and rock interface.
3) For the sake of convenience study and achievement application,putting forward a new mean that it describe quantificatively the soil and rock contected stratum with obliquity,area ratio,rigidity ratio and burial depth of the soil and rock interface.Analysising separate the influences of obliquity, area ratio, rigidity ratio, burial depth and excavate ways to the deformation rule of the soil and rock stratum tunnel wall rock and changed rule of lining structure internal force. Of these, the greatest impact is the depth and excavation methods, followed by the area ratio, angle and stiffness ratio.
4) The locked anchor tube should be bound by its rotation along the z-axis degree of freedom to consider. Anchor tube length and angle have a greater influence to the internal forces of the supporting structure.Appropriate length and angle is not only conducive to limit the deformation of rock,but also help to play the internal force of supporting structure.Determining the locked anchor tube effective or not and reasonable should consider it's influence to the deformation of wall rock and the internal force of supporting structure.Study results indicate that general soil tunnel the locked anchor tube should be 3.0m and lock pin into the anchor tube should be 30°.
5) Determining deep or shallow burial critical depth by coefficient of earth pressure is 2 times of hole diameter. Determining deep or shallow burial critical depth by inter and outer ratio of wall rock deformation is 1.7 to 3.0 times of hole diameter.
6) Through the above numerical simulation, we consider that excavating tunnel in the soil and rock stratum, it's supporting approach of the soil surrounding the hole should be appropriate to strengthen,especially in spandrel so as to ensure the unity and uniform deformation of supporting structure;We should make a reasonable layout in excavation approaches and reduce the disturbance of the soil. We also put forward to reduce the disturbance of the soil:"Preventing disturbance, and soil is emphases; Soil side strengthens to support,and spandrel is strengthen".
本文结合宝天高速公路黑岭段隧道工程,首先通过室内试验研究了黄土、砂岩以及土、岩接触面物理指标和力学性质；其次,通过建立土、岩接触带隧道计算模型,定量分析了隧道围岩变形规律和衬砌结构内力变化特征；再次,通过建立隧道开挖初期支护锁脚锚管的数值模型,分析了钢拱架锁脚作用机理和锁脚锚管的合理长度和打入角度；最后,通过土压力系数和围岩变形内表比探讨了隧道埋置的临界深度。主要得出以下成果：
1)土、岩接触面是一个软弱结构面,其抗剪强度主要取决于软弱黄土的强度特性。随着土、岩接触面处上覆黄土含水量的增加,接触面的粘聚力显著减小；摩擦角亦减小,且小于黄土的摩擦角。
2)土、岩接触带隧道围岩的变形主要表现为围岩沉降位移较大,不均匀沉降较明显；最大沉降位移位置一般在土、岩接触面土体侧。这种围岩变形导致隧道衬砌结构内力变化较大,主要表现为衬砌结构轴力和弯矩一般在土、岩接触面岩体侧较大。
3)提出了用土、岩接触面的倾角、面积比、刚度比和埋深来定量描述土、岩接触带的方法；分析了倾角、面积比、刚度比、埋深以及开挖方式对土、岩接触带隧道围岩变形规律和衬砌结构内力变化特征的影响。表明影响最大为埋深和开挖方式,其次是面积比、倾角和刚度比。
4)锚管的长度和角度对支护结构的内力均有较大的影响,适宜的长度和角度不仅有利于限制围岩的变形,而且有利于发挥支护结构的内力一般的土质隧道锁脚锚管宜取3.0m。锁脚锚管的打入角度宜取30°。
5)用土压力系数界定深、浅埋临界深度约为洞径的2倍；用围岩变形内表比界定深、浅埋临界深度为洞径的1.7～3.0倍。
6)在土、岩接触带中开挖隧道时,应适当加强洞周边土体侧的支护,尤其在土体侧拱肩处应加强支护,从而保证支护结构的变形统一均匀；应进行合理地布局分步开挖,减小对土层的扰动。提出了开挖方式和支护方案选取的原则,即“防止扰动,土为重点；土侧强支,拱肩加强”。
The strata including soil and rock often appear in mountain of loess zone which often covers with four Era. When the tunnel passes through the loess mountain, there are the shallow-buried broken wall rock with soil-rock interface, Such as Shenyan railway Yangma river tunnel, Xinsongshuwan tunnel in Longxi county of Gansu province and Lijun speedway tunnel in Shanxi and Baotian speedway heiling tunnel and so on. This kind of geological strata not only affacts the mechanical properties of tunnel evidently, but also hydro-geological conditions taking place change significantly, which resultes in the water content significantly increasing on the interface. Because the complex stratum with soil-rock interface doesn't arouse a wide range of people's attention, a number of incidents include landslides, and too large rock deformation occure in the past practice. It also prompts to study the necessity and urgency of the soil and rock contacted stratum tunnel wall rock.
Firstly, this paper studies physical index and mechanics index of loess, standstone and soil and rock's interface-by indoor test; Secondly,establishing a describe mean of soil and rock contected stratum, and qualitative and quantification evaluating the deformation of soil and rock marched with stratum tunnel wall rock and the internal force changing features of lining structure by numerical simulation; Thirdly,creating a numerical analysis mean of the locked anchor tube, anaslysing mechanism of action of steel rib locked feet and determining the rational length and infiltrate angle of the locked anchor tube; Finally,determining deep or shallow burial critical depth by coefficient of earth pressure and inter and outer ratio of wall rock deformation.Enduce mostly conclusion as follows:
1) The soil and rock interface forms shear failure surface easily. The shear strength of interface depends mainly on the strength characteristics of weak loess. With the loess water content increasing on the soil and rock interface, cohesive strength on the interface decreases significantly; Angle of friction attenuate little,but smaller than loess's.
2) The deformation features of soil and rock contected stratum tunnel wall rock manifest mainly on wall rock settlement displacement too big and settlement not equality.The maximum settlement displacement is not in the biggest dome and is in the dome away from the soil tend to the location of about 30°. This differential settlement caused internal forces changes large in the structure of the tunnel lining,it manifests mainly that lining structure axial force and bending moment are larger near the rock in the soil and rock interface.
3) For the sake of convenience study and achievement application,putting forward a new mean that it describe quantificatively the soil and rock contected stratum with obliquity,area ratio,rigidity ratio and burial depth of the soil and rock interface.Analysising separate the influences of obliquity, area ratio, rigidity ratio, burial depth and excavate ways to the deformation rule of the soil and rock stratum tunnel wall rock and changed rule of lining structure internal force. Of these, the greatest impact is the depth and excavation methods, followed by the area ratio, angle and stiffness ratio.
4) The locked anchor tube should be bound by its rotation along the z-axis degree of freedom to consider. Anchor tube length and angle have a greater influence to the internal forces of the supporting structure.Appropriate length and angle is not only conducive to limit the deformation of rock,but also help to play the internal force of supporting structure.Determining the locked anchor tube effective or not and reasonable should consider it's influence to the deformation of wall rock and the internal force of supporting structure.Study results indicate that general soil tunnel the locked anchor tube should be 3.0m and lock pin into the anchor tube should be 30°.
5) Determining deep or shallow burial critical depth by coefficient of earth pressure is 2 times of hole diameter. Determining deep or shallow burial critical depth by inter and outer ratio of wall rock deformation is 1.7 to 3.0 times of hole diameter.
6) Through the above numerical simulation, we consider that excavating tunnel in the soil and rock stratum, it's supporting approach of the soil surrounding the hole should be appropriate to strengthen,especially in spandrel so as to ensure the unity and uniform deformation of supporting structure;We should make a reasonable layout in excavation approaches and reduce the disturbance of the soil. We also put forward to reduce the disturbance of the soil:"Preventing disturbance, and soil is emphases; Soil side strengthens to support,and spandrel is strengthen".
引文
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[10]蒋建平,章杨松,高广运等.土体中第四纪断层结构面特征及其地震和岩土工程意义[J].西北地震学报,2002,24(3)：215～219.
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[2]中国科学院地质研究所工程地质与抗震研究室.岩体工程地质力学的原理和方法[J].中国科学,1972,(1)：56～62.
[3]中国科学院地质研究所.谷德振文集[M].北京：地质出版社,1994.
[4]王思敬,杨志法,刘竹华.地下工程岩体稳定分析[M].北京：地质出版社,1984.
[5]孙广忠.岩体力学的进展—岩体结构力学[J].岩石力学与工程学报,1991,10(2)：112～116
[6]蒋建平,罗国煜.土坡中的优势结构面分析[J].工程地质学报,2000,8(4)：438～441.
[7]蒋建平,章杨松,罗国煜,阎长虹.优势面理论在岩土工程中的应用[J].水利学报,2001,55(8)：90～95.
[8]蒋建平,章杨松,罗国煜.基于土体中结构面的岩土工程问题探讨[J].工程地质学报,2002,10(2)：160～165.
[9]蒋建平,章杨松,罗国煜.土体宏观结构面及其对土体破坏的影响[J].岩土力学,2002,23(4)：482～485.
[10]蒋建平,章杨松,高广运等.土体中第四纪断层结构面特征及其地震和岩土工程意义[J].西北地震学报,2002,24(3)：215～219.
[11]杜时贵.岩体结构面的工程性质[M].北京：地震出版社,1999.
[12]何满潮,竞海河,孙小明.软岩工程力学.北京：科学出版设,2002
[13]王永岩.软岩巷道变形与压力分析控制及预测.辽宁工程技术大学博士学位论文,2001.06
[14]傅冰峻.国际岩石力学发展动向.岩石力学与工程学报,1996,No.1,344～351
[15]何满潮,黄福昌,闫吉太.软岩工程技术现状与展望.世纪之交软岩工程技术现状与展望.北京：煤炭工业出版社,1999.04,33～41
[16]徐干成,白洪才,郑颖人,刘朝.地下工程支护结构.北京：中国水利水电出版社,2001
[17]孙广忠.岩体结构力学,北京,科学出版社,1998.
[18]于学馥,郑颖人等.地下工程围岩稳定分析.北京：煤炭工业出版社,1983.
[19]王思敬,张菊明.岩体结构稳定分析原理和方法.地质科学,第1期,1976.
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