软岩小净距隧道施工力学效应研究

以软岩小净距隧道在不同开挖方式下达到稳定后围岩和复合衬砌的力学效应为对象,重点分析不同开挖方式下锚杆、喷射混凝土层和二次衬砌的受力特点,考察不同净距对中夹岩柱塑性区的影响.结果表明：施工小净距隧道应慎重选择后继施工隧道的开挖方式;后继隧道施工的开挖方式直接对先行既有隧道锚杆、喷射混凝土层和二次衬砌应力状态产生很大影响;中夹岩柱塑性区大小与净距紧密相关,同时,隧道埋深和围岩类别也是影响塑性区大小的重要因素.     

Full 3D modelling for effects of tunnelling on existing support systems in the Sydney region

The assessment of the interaction between a new tunnel and existing structures is an important issue in urban areas. In this study, the effect of tunnelling on the existing support system (i.e. shotcrete lining and rock bolts) of an adjacent tunnel is firstly investigated using ABAQUS and TUNNEL3D through full three-dimensional (3D) finite element calculations coupled with elasto-plastic material models, which takes into account the tunnelling procedure, the interaction between the shotcrete lining and rock mass, the interaction between the rock bolts and rock mass, and the elasto-plastic behaviour of the rock mass, the shotcrete lining and the rock bolts. Then, on the basis of the calculated results, it is concluded that the driving of the new tunnel significantly affects the existing support system when the advancing tunnel face passes the existing support system and is minor when the face is far from it. Moreover, the support system in the side of the existing tunnel closest to the new tunnel is more significantly affected than that on the side opposite to the new tunnel. It is also found that in a region such as Sydney with relatively high horizontal regional stresses, the driving of the new tunnel will not cause considerable adverse effects on the existing support system, if the new tunnel is driven horizontally parallel to the existing tunnel with a sufficient separation, since both the tensile stress in the existing shotcrete lining in the lateral sides of the preceding tunnel and the compressive stress at the crown decrease although noticeable tensile stress increments are observed on some parts of the existing rock bolts. Finally, it is pointed out that the effects of tunnelling on the existing support system strongly depend on the position between the original and new tunnels. In terms of the stress increments on the existing support system, especially the maximum tensile stress increments on the existing shotcrete lining, the driving of the new tunnel causes increasingly adverse effects on the existing support system in a sequence of: (i) horizontally parallel tunnels with a separation of 30 m; (ii) horizontally parallel tunnels with a separation of 20 m; (iii) staggered tunnels with a separation of 30 m; (iv) vertically alignment tunnels; and (v) staggered tunnels with a separation of 20 m in the cases investigated in this study. For the relatively high regional stresses in the Sydney region, the obtained results qualitatively agree with other’s published observations from the construction of closely parallel subway tunnels.     

小间距浅埋隧道的支护设计探讨

利用奥地利大型岩土工程有限元数值计算软件FINAL计算结果比较研究认为，在新奥法施工的小间距平行土质浅埋隧道中，对于中间岩柱的支护与设计，只要衬砌受力在合理范围内，不需要特别考虑中间岩柱的稳定性，而对其加设锚杆或者其他支护辅助手段，隧道之问的间距可以达到1．0m，甚至更少。列举了慕尼黑地铁隧道对这一结果的成功应用。对于近距离双孔平行隧道，两隧道相互之间的影响，不仅与围岩类别、隧道间距、开挖和支护方式有关，而且不同的开挖顺序，会有不同的结果。分析结果表明，如果先修建好一孔隧道，再修建另一孔隧道，第---~L隧道的修建会对第一孔隧道，特别是相近一侧有较大的影响，仰拱处容易出现拉应力；如果两孔隧道同时交替掘进，则隧道相互影响较大，第一孔隧道的底部和第二孔隧道的拱部，容易出现拉应力，总体衬砌受力比第一种开挖支护方式要小。两种开挖支护方式中，中间岩柱两侧土体和衬砌均处于受压状态。慕尼黑地铁U6段相距0．8m，两隧道的成功修建和运营，是对本文结论的成功验证。     

软岩隧道施工特性及其动态力学行为研究

采用三维快速有限差分软件，以软岩小净距隧道在不同施工方式下达到稳定后围岩和复合衬砌的力学效应为对象，重点分析不同施工方式下锚杆、喷射混凝土层的受力特点，以及洞周围岩特征点的变形和府力。对推荐的施工方式，分析了锚杆轴力、喷射混凝土层弯矩随开挖顺序的变化过程。计算结果表明：施工小净距隧道应慎重选择后继施工隧道的开挖方式，后继施工隧道的开挖方式直接对先行既有隧道锚杆、喷射混凝土层的应力状态产生很大影响。提出了复合衬砌应重点关注的薄弱部位和可能采取的工程措施。     

卵砾石土层大跨公路隧道初期支护优化研究

 江苏省宁常高速公路茅山隧道位于卵砾石土层斜坡中,具有浅埋、大跨扁平的特点,结合现场大型剪切试验分析、获取卵砾石层剪切强度参数,采用弹塑性非线性有限元法模拟并分析开挖和支护的全过程。根据新奥法,喷混凝土是公路隧道施工中体现初期支护柔性支护特点的主要因素之一,针对卵砾石土层II类软弱围岩浅埋地段交叉中隔壁法实际施工工艺特点,选择拱顶区右上部、中轴线、左上部3个测点下沉值(S1,S2,S3)建立协方差函数,并结合围岩和二衬塑性区的分析,对初支喷混凝土厚度进行合理性研究,提出该隧道卵砾石土层拱顶埋深在26 m左右断面最合理的初支喷混凝土厚度为22～28 cm,该典型断面最优初支喷混凝土厚度为26 cm,该研究成果对斜坡浅埋软弱II类围岩地段交叉中隔壁法施工设计有一定参考价值     

Interaction of shotcrete with rock and rock bolts—A numerical study

The shotcrete–rock interaction is very complex and is influenced by a number of factors. The influence of the following factors was investigated by a series of numerical analyses: the surface roughness of the opening, the rock strength and Young's modulus, the discontinuities, the extent and properties of the excavated disturbed zone, the mechanical properties of the interface between shotcrete and rock, and the thickness of the shotcrete lining and the rock bolts. The study was carried out as a sensitivity analysis. The results showed that the rock strength and the surface roughness had significant impact on the number of failures at the rock–shotcrete interface and in the shotcrete lining. Furthermore, the behaviour of the lining is sensitive to small amplitudes of the surface roughness. In all the cases investigated, a high interface strength was favourable. The results indicate that if a thick shotcrete lining is dependent on the bond strength. The benefit of using a thicker lining can be doubtful. The analyses showed that for an uneven surface the extent of the EDZ had a minor effect on the behaviour of the shotcrete lining. Furthermore, if rock bolts were installed at the apex of the protrusion instead of at the depression, the number of failures decreased both at the interface and in the lining.     

隧道钢纤维喷射混凝土性能试验及其工程应用

 根据钢纤维喷射混凝土结构力学原理,为了研究钢纤维混凝土喷层在隧道单层永久衬砌支护中适用性,先分析钢纤维在混凝土中的增强力学作用机制,然后完成钢纤维喷射混凝土合理配比、抗拉、抗压、抗折及抗折初裂强度和弯曲性能等指标的室内试验;并结合具体的隧道现场喷射试验,以及围岩应力、钢纤维混凝土喷层应力及洞周附加水平收敛等监测数据进行分析。研究结果表明,钢纤维喷混凝土抗拉、抗折强度高,韧性好,喷层中的应力分布较均匀,具有较好的让压能力,喷射作业回弹损失量减少,说明钢纤维喷射混凝土是一种理想的单层衬砌支护材料,具有较好的推广应用价值。     

喷锚支护在公路隧道复合式衬砌施工中的应用

以陕西秦岭公路隧道复合式衬砌中喷锚支护实际施工为例,对喷锚支护在不同围岩中的作用及施工工艺进行了探讨,针对隧道施工具体情况,选择合理的支护技术,以达到支护性能和经济效益的最佳组合。     

Rock falls in selected Norwegian hydropower tunnels subjected to hydropeaking

Unlined rock-blasted hydro tunnels are key components of the Norwegian hydropower system (NHS), used both as water collectors and conveyors. Long-term stability of these constructions is essential to ensure continuous and cost-effective operation. Recent trends in the energy market have led to so-called hydropeaking production patterns, which increase the frequency of unsteady flow situations in the hydro tunnels. Such production patterns can trigger structural instability in the tunnel systems in form of rock falls, which reduces the cross-sectional area and cause head loss. This work examines the quantity of rock falls in hydropower tunnels subjected to hydropeaking through a series of inspections. The results indicate that the frequency and total volume of rock falls increases if a tunnel is subjected to hydropeaking.     

穿越软硬围岩隧道设置减震层振动台试验研究

以西部高烈度地震区浅埋公路隧道为依托,通过大型振动台模型试验,研究隧道穿越软硬围岩段在地震荷载作用下设置减震层的动力响应特性,并采用数值模拟方法对试验结果进行验证分析。试验及数值计算结果表明,从洞身段来看,减震层厚度存在最优值;从穿越软硬围岩段来看,增加减震层厚度可降低隧道沿纵向的动力响应差异,但加速度峰值会有所上升;拱顶围岩和隧道衬砌结构加速度响应频谱曲线均表现出“三峰值”现象,设置减震层并不会显著改变围岩频谱特性,衬砌结构也不显著体现自振特性,其响应主要取决所穿越围岩的动力特性;减震层处于最优值时可通过吸收更多的低频组分来降低隧道的动力响应;设置减震层可显著降低二衬动应力,但会使初支动应力呈现不同程度的放大,随减震层厚度的增加,二衬动应力先减小后增大,初支动应力先增大,后呈降低趋势;通过观察衬砌破坏形态,隧道拱顶、拱脚和仰拱易发生开裂,设置减震层后,仰拱相对容易发生破坏,应给予重点关注。研究成果可为西部高烈度地震区浅埋隧道抗震设计提供参考。     

Single-shell In-situ concrete tunnel lining: Experience in the Federal Republic of Germany

Although traffic tunnel construction in West Germany typically has used in-situ concrete as a double-shell lining, this method is both time-consuming and costly to apply. Recent research efforts have focused on the possibilities of single-shell in-situ concrete tunnel lining. This paper describes tests performed recently in West Germany on the use of (1) shotcrete and (2) steel-fibre-reinforced pumped concrete. The discussion deals with problems involved in these types of construction, the site and laboratory tests performed, and recommendations/prospects for application of these types of tunnel linings. The article also reports on two recent research projects, involving: (1) tunnel lining for large cross-sections with steel plate skin and unreinforced backfill concrete; and (2) construction and economic possibilities for creating tunnels in monocoque design.     

Impact of fire on tunnels in Hawkesbury sandstone

The majority of tunnels in Sydney, Australia are within near-saturated Hawkesbury sandstone. Crown support in these tunnels typically comprises permanent rockbolts, and shotcrete ranging in thickness from about 75 mm to 250 mm. Sidewalls are mostly exposed sandstone with occasional rockbolts, and, in places, a thin shotcrete skin for surface protection.Rock will quickly be exposed to high temperature in a tunnel fire where no, or a thin layer of shotcrete exists. Rock with thicker shotcrete may also be exposed where spalling of the shotcrete occurs.The phenomenon of spalling in fire has been widely researched for concrete and, to a lesser extent, shotcrete [e.g. Tatnall, P.C. 2002. Shotcrete in fires: effects of fibers on explosive spalling. Shotcrete, 10–12]. It is assessed as being primarily associated with steam pressures produced by evaporation of water in pores [Hertz, K.D. 2002. Limits of spalling of fire-exposed concrete. Fire Safety Journal 38, 103–116].This paper assesses, by means of laboratory and field tests, how exposed sandstone is likely to respond in a tunnel fire.It is concluded that substantial explosive spalling will occur early and at relatively low temperatures. This spalling could create dangerous conditions for rescue, and escaping personnel. However, beyond the zone of spalled sandstone there would be only minor structural impact on the rock mass.     

隧道初支与二衬间接触压力统计分析

复合式衬砌一般由初期支护和二次衬砌共同组成,二者相互作用关系是隧道工程中的研究热点,本文通过对43座隧道79个监测断面初支与二衬接触压力的统计分析,探讨了接触压力的总体分布特征及其与围岩等级、隧道埋深、跨度等因素的关系,研究了二衬荷载分担比在洞周的分布规律,讨论了接触压力随时间的变化规律及其空间分布特征。结果表明:初支与二衬接触压力值分布在10~200 kPa之间;接触压力及其离散程度随隧道埋深增大而增大,Ⅴ级围岩增大趋势比Ⅳ级围岩更明显;二衬荷载分担比集中在0~20%范围内;接触压力有明显的时间效应,随时间的变化表现为快速增长至峰值之后减小,进而缓慢增大趋于稳定,稳定所需时间在二衬浇筑后30 d左右;接触压力空间分布规律为拱顶→拱肩→拱腰→拱墙增大,拱墙→拱脚→拱底减小。研究结论可为隧道结构受力分析与优化提供参考。     

浅埋黄土隧道衬砌结构受力分析

通过对三十里铺隧道的现场测试,研究浅埋黄土隧道一衬和围岩接触应力、锚杆轴力、喷射混凝土表面应变、二衬中钢筋应力和浇注混凝土应变随时间变化规律及分布特征。结果表明,围岩释放应力最大值在7～10 d,位置在拱腰处;锚杆轴力稳定时间为30 d左右,且在空间上出现压应力区;喷射混凝土表面应变较大且常出现跳跃性变化;二衬钢筋应力初期为拉应力;边墙处的稳定时间为6～8 d后,拱顶处30 d后仍然递减;二衬混凝土应变由初期的拉应变向压应变变化。隧道衬砌的受力分析结果为支护系统的优化提供依据,对同类工程的设计提供借鉴。     

Adhesion strength and shrinkage of shotcrete

Shotcrete is widely used as rock support in mines and in civil engineering projects. In many cases the adhesion between the shotcrete and the rock is one of the most important properties.The objective of this study was to: (i) identify typical failures of shotcrete in a mining environment, (ii) measure the growth of the adhesion strength of shotcrete with respect to age, (iii) investigate the influence of surface treatment (scaling and cleaning) on the adhesion strength of shotcrete and (iv) investigate the occurrence of shrinkage cracks in the shotcrete and failures in the interface between the shotcrete and the rock.The failure mapping showed that most of the observed failures of shotcrete are in areas with a thin shotcrete layer (<20 mm) together with a low adhesion strength. Furthermore, the measured average thickness of shotcrete (40 mm) was almost the same as the ordered thickness, the problem is the wide scatter. In 18% of the thickness measurements, the shotcrete thickness was less than or equal to 20 mm. If the shotcrete lining in the mine has the same thickness distribution as during the tests, the supporting ability of as much as 18% of the shotcrete lining can be considered as more or less negligible.No differences in free shrinkage were observed between plain and steel fibre reinforced shotcrete. Relatively large areas with lack of contact between shotcrete and wall were observed in the shrinkage tests. This indicates that restrained shrinkage can destroy the bond between the shotcrete and rock. The results from the restrained shrinkage tests show the importance of the bond at the interface. If bond failure occurs, the ability to distribute and control the crack width ceases.The growth of the adhesion strength on a sandblasted concrete wall and the growth of the compressive strength showed a correlation. However, the scatter in the results indicates that further investigations have to be done in order to establish a reliable relation between the growth in adhesion and compressive strength with age. The results from the field tests showed that the adhesion strength was significantly higher on rock surfaces that had been water jet-scaled (with 22 MPa water pressure) than those treated by mechanical scaling followed by cleaning of the rock surface (water pressure 0.7 MPa).     

浅埋黄土隧道衬砌结构受力分析

 通过对三十里铺隧道的现场测试,研究浅埋黄土隧道一衬和围岩接触应力、锚杆轴力、喷射混凝土表面应变、二衬中钢筋应力和浇注混凝土应变随时间变化规律及分布特征。结果表明,围岩释放应力最大值在7～10 d,位置在拱腰处;锚杆轴力稳定时间为30 d左右,且在空间上出现压应力区;喷射混凝土表面应变较大且常出现跳跃性变化;二衬钢筋应力初期为拉应力;边墙处的稳定时间为6～8 d后,拱顶处30 d后仍然递减;二衬混凝土应变由初期的拉应变向压应变变化。隧道衬砌的受力分析结果为支护系统的优化提供依据,对同类工程的设计提供借鉴。     

城门洞型压力隧洞衬砌限裂配筋设计方法研究

以城门洞型无压隧洞改建为引水发电隧洞的限裂配筋设计方法为研究对象,综合分析衬砌开裂前后围岩–衬砌混凝土–钢筋的联合作用,建立起二维(平面应变问题)非线性有限元数值仿真分析模型,经分析得到运行期内水压力工况下衬砌中钢筋应力、衬砌混凝土拉应力、衬砌裂缝、裂缝宽度的分布规律、衬砌配筋设计结果,以及检修期外水压力工况下衬砌混凝土裂缝处的应力集中现象和衬砌配筋的验算结果。提出的衬砌限裂配筋设计方法较以往的方法考虑更多影响配筋结果的因素,使结果更符合水工压力隧洞的实际工况,对同类工程设计具有指导意义。     

盾构隧道双层衬砌横向力学结构参数优化研究

随着水下盾构隧道建设及运营环境日益复杂,安全要求日益提高,盾构隧道双层衬砌有望在工程中得到较为广泛的应用。本文依托武汉轨道交通8号线越江隧道工程,采用双层衬砌盾构隧道三维壳—弹簧力学分析模型,研究了不同工况下二次衬砌强度及厚度对双层衬砌内力及变形的影响,并对二次衬砌是否应当配筋的问题进行了探讨。研究结果表明:二次衬砌强度变化对管片衬砌结构内力影响甚微,但二次衬砌弯矩量值略有提高,同时通过提高二次衬砌强度来抑制隧道竖向变形的效果不明显,考虑到工程造价问题,二次衬砌强度不宜过高,取C40为宜;二次衬砌厚度增加对管片横向内力影响甚微,但对其结构受力有不利影响,综合考虑隧道运营期火灾以及列车撞击等因素,二次衬砌厚度取30~40 cm为宜;在外荷载增大情况下,二次衬砌拉应力量值显著增加,超过混凝土规范容许拉应力值,因此,实际工程中建议对二次衬砌进行配筋设计。研究结论可为盾构隧道双层衬砌的设计及施工提供有益的借鉴。     

海底隧道最小岩石覆盖厚度确定方法研究

目前国内正在修建或拟修建多条海底隧道,其最小岩石覆盖厚度是海底隧道纵断面线路设计的主要参数之一,将直接制约着海底隧道的安全和工程造价。为此,开展了确定海底隧道最小岩石覆盖厚度的确定方法和准则研究,并综合分析了各种不同方法确定的海底隧道最小岩石覆盖厚度对最终岩石覆盖厚度的权重影响。通过加权的方法得到了确定海底隧道最小岩石覆盖厚度的方法和原则。最后结合工程实例,应用上述方法,得到了宁波象山港海底隧道最小岩石覆盖厚度。     

隧道围岩-喷射混凝土界面应力解析

根据喷射混凝土支护隧道围岩的界面力学特点,考虑喷层与围岩结合界面受力和变形协调关系,并结合围岩承载拱效应,建立了围岩喷层结构的复合曲梁共同承载模型,然后通过各微单元静力平衡推导复合曲梁的径向位移的控制微分方程,得到任意分布荷载作用下喷层与围岩界面应力以及喷层与围岩各自内力的解析式,可迅速获取喷层与围岩结合界面的力学状况,进而判断围岩稳定性与预测安全性,为隧道施工决策提供技术支撑。最后经隧道台阶法开挖的算例研究表明,喷层支护通过其与围岩的结合界面上传递应力使围岩内部形成压应力带,有利于围岩的稳定。