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1.
To analyze the stability of a shallow square tunnel, a new curved failure mechanism, representing the mechanical characteristics
and collapsing form of this type of tunnel, is constructed. Based on the upper bound theorem of limit analysis and the Hoek-Brown
nonlinear failure criterion, the supporting pressure derived from the virtual work rate equation is regarded as an objective
function to achieve optimal calculation. By employing variational calculation to optimize the objective function, an upper
bound solution for the supporting pressure and the collapsing block shape of a shallow square tunnel are obtained. To evaluate
the validity of the failure mechanism proposed in this paper, the solutions computed by the curved failure mechanism are compared
with the results calculated by the linear multiple blocks failure mechanism when the Hoek-Brown nonlinear failure criterion
is converted into the Mohr-Coulomb linear criterion. The influences of rock mass parameters on the supporting pressure and
collapsing block shape are discussed. 相似文献
2.
李彦民 《福建工程学院学报》2019,(6):539-544
为研究地面线路运营对下穿盾构隧道结构的影响规律,基于相似比理论建立室内大型试验模型,模拟上部列车荷载作用下土层及其内部盾构隧道结构的受力变形过程,总结变形规律。结果表明,模型试验能够较好地反映外部荷载影响下土层以及内部盾构隧道结构的受力和变形特性;地表列车荷载在土层传递过程中,同一层面上沿地面线路方向的土压力大于两侧土压力,远离线路的地层受列车荷载影响相对较小,同一竖向截面土压力变化量由上至下逐渐减小,即外部荷载对浅层土的影响明显大于深层土;盾构隧道在地表列车行驶过程中,环向出现背车面受拉迎车面受压的受力特性,呈斜向压扁,纵向应变从中间交叉点向盾构隧道两侧逐渐减小,呈下凹压弯;盾构隧道埋深越小,受地表荷载影响越显著,增大一倍埋深对应纵向应变最大值减小约44.5%。 相似文献
3.
以南宁地铁一号线南湖段下穿隧道为工程背景,建立隧道开挖的三维有限元模型,通过数值分析,得到盾构施工过程中地层变形的分布规律,讨论盾构施工过程中注浆压力对地表沉降、水平位移及拱顶位移的影响,分析掌子面压力对地表隆起的影响规律。研究结果表明,注浆压力对地表变形会产生明显的影响,随着注浆压力的增大,地表沉降及水平位移明显减小。当掌子面压力大于0.1 MPa时,会引起掌子面前方土体产生向上的位移,地表隆起量随掌子面压力的增加而增大。 相似文献
4.
In most studies of tunnel boring machine(TBM)tunnelling, the groundwater pressure was not considered, or was simplified and exerted on the boundary of lining structure. Meanwhile, the leakage, which mainly occurs in the segment joints, was often ignored in the relevant studies of TBM tunnelling. Additionally, the geological models in these studies were simplified to different extents, and mostly were simplified as homogenous bodies. Considering the deficiencies above, a 3D refined model of the surrounding rock of a tunnel is firstly established using NURBS-TIN-BReP hybrid data structure in this paper. Then the seepage field of the surrounding rock considering the leakage in the segment joints is simulated. Finally, the stability of TBM water diversion tunnel is studied coupled with the seepage simulation, to analyze the stress-strain conditions, the axial force and the bending moment of tunnel segment considering the leakage in the segment joints. The results illustrate that the maximum radial displacement, the minimum principal stress, the maximum principal stress and the axial force of segment lining considering the seepage effect are all larger than those disregarding the seepage effect. 相似文献
5.
煤与瓦斯突出严重影响了矿井安全生产,开采保护层是最有效、最经济的防治措施;通过对海孜矿上保护层开采效果研究,结果表明：开采前后瓦斯压力及含量降低明显,卸压区内瓦斯抽采率可达33.2%;卸压区内煤层透气性系数比未卸压区的增大三倍;相似模拟实验表明9煤的膨胀率为8.1‰,综合分析确定开采上保护层后对9煤起到了明显的卸压保护作用,研究结果为相似条件下保护层开采提供了参考。 相似文献
6.
The indirect boundary element method (IBEM) is used to study the surface motion of an alluvial valley in layered half-space for incident plane P-waves based on Wolf’s theory. Firstly, the free field response can be solved by the direct stiffness method, and the scattering wave response is calculated by Green’s functions of distributed loads acting on inclined lines in a layered half-space. The method is verified by comparing its results with literature and numerical analyses are performed by taking the amplification of incident plane P-waves by an alluvial valley in one soil layer resting on bedrock as an example. The results show that there exist distinct differences between the wave amplification by an alluvial valley embedded in layered half-space and that in homogeneous half-space and there is interaction between the valley and the soil layer. The amplitudes are relatively large when incident frequencies are close to the soil layer’s resonant frequencies. 相似文献
7.
杨光煦 《长江工程职业技术学院学报》1999,(2)
总结了九江江堤溃口段复堤设计经验。阐述堤防地基渗流控制应确保有一定渗径长度,防止产生渗透破坏,减少作用在防洪墙底板上的扬压力。采用迎水侧具有隔渗作用的格栅状深层搅拌桩结构,可提高地基承载力,消除不均匀沉降,确保地基抗滑及抗渗稳定。 相似文献
8.
A case study of a significant surface settlement induced by tunneling in permeable strata with the shallow tunneling method is presented in this paper. The measurements of surface settlements along the excavation direction were first analyzed to highlight the impacts of groundwater seepage. Due to the groundwater inflow inside a double-arched tunnel, the surface settlement developed to a high level far beyond the measured crown settlement. The settlement-affected zone extended to 4 times the tunnel height ahead of the forefront heading and 1.5 times the tunnel height behind the hindmost heading. Consolidation resulting from high pore pressure change was considered to be the main mechanism for the large surface settlements. In addition, a 3D fluid-mechanical coupled numerical analysis was carried out to confirm the relationship between the significant surface settlement and pore pressure variation. This analysis reveals that lowering the permeability of the small pipe grouting zone, especially of the primary lining, could lessen the drop in pore pressure in the overlying strata, further reducing the total surface settlement. The numerical results also suggest that the transverse range of vertical displacement could be quite wide, and the settlement developed integrally from the tunnel crown towards the ground surface due to groundwater seepage. Moreover, the effect of advance drainage on surface settlement was investigated based on the same numerical model. Drainage with horizontal boreholes could considerably increase the safety of tunnel heading but had limited impact on surface settlement. Finally, the applications of pre-grouting and advance drainage measures were discussed for tunneling cases in permeable strata. 相似文献
9.
Pressurized bentonite slurry is applied on a tunnel face to form a filter cake to stabilize the tunnel face when the slurry shield excavates through the sandy soil. Failure of the tunnel face may be caused by a high permeable filter cake, which commonly has a long penetration distance of slurry in sands. A column system with a height of 680 mm and a diameter of 300 mm was developed to model pressurized slurry infiltration in sands. Pressure transducers were installed to estimate the hydraulic conductivity of the filter cake during slurry infiltration. The electrical conductivity of the leachate of collected samples was measured. Results show that the majority of fine particles in slurry are within the range 100–300 mm into the sand specimen. The time for forming an impermeable filter cake is about 300 s, which indicates the impermeable filter cake is hard to form during the excavation. 相似文献
10.
在使用瑞利波对隧道进行地质超前预报时,经常会遇到掌子面积水的情况。文章从分析瑞利波的波动方程入手,将掌子面积水假定为自由面上覆盖一层非弹性覆盖层,以此为基础推导出积水对瑞利波传播的影响方程,认为掌子面积水情况下,受到垂直应力的作用瑞利波发生频散,同时岩体质子的振动也会由于外界水体的存在而受到黏滞力的影响,瑞利波周期变大、频率变小。但是经过深入研究和结合工程实例,发现这种影响仅仅停留在积水层表面,对整个工程地质超前预报没有明显影响。 相似文献
11.
锦屏二级水电站深埋隧洞渗控研究 总被引：3，自引：0，他引：3
王美芹 《长江工程职业技术学院学报》2003,20(4):26-28
用降雨入渗渗流有限单元法对锦屏二级水电站深埋隧洞最大埋深断面渗流场的水头分布进行了数值模拟。结合工程的现拟渗控措施经多种计算方案的求解，较详细地综合分析了各计算方案的渗控情况与特点，并获得了该断面隧洞支护上的外水压力及最优的渗控方案。 相似文献
12.
蔡德智 《延安教育学院学报》2012,26(3):106-107
隧道路面排水基层,在隧道路面工程中起着相当重要的作用,它既要承担行车荷载,还要排除部分来自路面清洁、消防、行车和隧道围岩的渗水。就现行《公路隧道施工技术规范JTGF60-2009》、《公路隧道设计规范JTGD70-2004》非常粗略,并无隧道路面结构层及原材料相关技术标准要求,在实际施工过程中,只能完全依赖设计文件要求或参考其他资料进行相关试验。这样以来一：给施工、及工程管理带来不便,二：无形中给工程埋下质量隐患。 相似文献
13.
大龙潭水利枢纽大坝基础为近于直立的层状岩体,坝体上下游为岩溶强烈发育的灰岩分布区,左右两岸岩体中分布有大量顺河向断裂,成为绕坝渗流的通道.为了监测坝址两岸蓄水前后的地下水运移状况,了解工程运行期地下渗流场的变化规律,建立了大龙潭水利枢纽大坝防渗帷幕渗流监测网. 相似文献
14.
朱占虎 《河北能源职业技术学院学报》2004,4(3):64-64,71
通过架棚巷道支护结构分析,架棚巷道破坏原因多是由于巷道的侧压力和底鼓引起,造成棚子相对下沉,使巷道变形、断面变小,采取在巷道两墙打锚杆和棚脚穿钢筋混凝土鞋后巷道围岩对侧压力减小了,支架支承能力增强,提高了巷道的稳定性。 相似文献
15.
土石坝的除险加固方案中常采用冲抓套井回填夯实粘土作为防渗体,即粘土心墙防渗体,该方法已在许多水库和相当长度的堤防工程建设中得到广泛的应用;然而其渗透稳定一直是工程设计和施工中的关键问题之一.本文结合某水库土石坝除险加固工程坝体渗透稳定问题,开展了坝体心墙粘土的物理特性、渗透特性、临界坡降的研究,为工程设计和施工提供了必要的分析成果和参考依据. 相似文献
16.
王睿 《河北职业技术学院学报》2010,(2)
隧道工程是构筑在地表之下的结构物,因而总是处在各种地下水的包围之中。在隧道设计、施工或使用过程中任何有害扰动都会造成隧道防排水体系的缺陷,从而引起隧道渗水。文章从多方面对隧道渗水的原因展开讨论,并结合我国隧道工程施工技术现状,提出隧道渗漏水的防治措施。 相似文献
17.
18.
我国绝大部分采煤工作面均采用"U"型通风方式,其落山角是采空区瓦斯的集中涌出区域。本文通过对综采工作面落山角瓦斯来源和瓦斯超限原因的分析,探索出一套"两进两回"治理落山角瓦斯的通风方式。该方式能有效提高局部积聚区域内瓦斯扩散强度,并能加强巷道中风流的瓦斯运移,治理落山角瓦斯简单易行、稳定可靠,有较好的推广应用价值。 相似文献
19.
窦仲四 《淮南职业技术学院学报》2010,12(4)
以皖北五沟矿井1011采掘工作面的测井钻孔资料及岩土试验报告为依据,按照该采掘面的实际情况,按照一定建模原则,设计两个计算模型:走向模型Ⅰ和倾向模型Ⅱ,分析开采后上覆岩层移动演化特征,分别从覆岩横向、竖向移动规律进行探讨,从而预测冒落带的分布、导水裂隙带的高度。 相似文献
20.
矫永刚 《福建工程学院学报》2020,(1):46-52
以滨海软土地层中盾构隧道平行上穿既有隧道为背景,通过数值仿真软件对开挖动态过程进行了精细化模拟,研究盾构隧道施工顶推力对周边地层及其内部既有隧道受力变形的影响。结果表明,在新建隧道上穿施工过程中,开挖扰动对地层的影响范围主要集中在距离开挖面-1.0~1.5D区域内(D为盾构隧道外径),扰动效果以新建隧道轴线为中心呈环状向外扩散,盾构顶推力从0.1MPa增至0.4MPa时,地表变形及1.0D范围内地层压力均增大20%以上;新建隧道平行上穿既有隧道过程中,既有隧道断面变形从横向鼓曲变为竖向拉伸,且整体出现上浮现象,顶推力达0.3MPa后,既有隧道拱底和拱顶隆起速度增加,以拱底为基准,顶推力自0.1MPa增加至0.4MPa时,隧道上浮量增大34.2%;施工过程中除保证常规地表变形监测外,对于近接平行上穿施工还需加强对既有隧道竖向变形的监控,必要时采取结构加固措施和施工参数综合调整办法,以降低开挖扰动对周边地层和结构物的影响。 相似文献