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1.
The presence of a gassy ground condition is an important problem in tunneling. In this study, the effects of groundwater H2S and CH4 emissions are investigated and characterized together with the factors that created these conditions in Nosoud tunnel in Iran. Through the geological investigations, the presence of these gasses was not detected prior to the construction of the tunnel. Groundwater sampling indicated that about 1 L of H2S is released per 100 L of the water inflow into the Nosoud tunnel under normal conditions. However, the volume of the released gas was varying with the changes in the groundwater discharge rate. Thus, estimation of groundwater inflow into the tunnel is necessary for predicting the volume of gas emission. Based on the experience of the Nosoud tunnel excavations, there are several geological and hydrogeological factors that must be considered as the indicators of gas emissions during tunneling. Considering the importance of ground water gas emission into the tunnels located in gassy conditions, the present work was conducted to predict the H2S seepage before the excavation using geological and hydrogeological indicators. 相似文献
2.
Ghassem Jalilian Khave 《Geotechnical and Geological Engineering》2013,31(5):1621-1638
In the late December of 2006 while Zagros tunnel project in western Iran was advancing according to the schedule, a sudden rush of groundwater accompanied by a nauseating odor similar to that of rotten egg intruded the tunnel. Some workers complained from eye and respiratory tract irritation. The presence of hydrogen sulfide (H2S) gas as high as 200 ppm was soon tested positive by gas detectors and subsequently the ventilation fans (2*110 kW) speed were boosted to 1,450 rpm in order to dilute the gas concentration to safe levels (10 ppm). Nonetheless, the work continued at a rather moderate pace for another 11 days and 134 more meters excavated in the gas infested grounds before 4 men died during a damage assessment survey of the TBM after a power failure that had forced the tunnel ventilation system to temporarily shut down. This paper is to discuss hazards and geological sources of H2S gas in of Zagros Water Conveyance Tunnel and to recommend practical solutions to prevent or mitigate the gas destructive effects on human and machinery, as well. 相似文献
3.
本文在梳理前人研究成果的基础上,结合野外实地调查和样品分析数据,分析了四川成都龙泉山城市森林公园的主要环境问题。研究表明,龙泉山城市森林公园总体地质环境条件较好,其总体规划和地质环境相适宜,在建设过程中需要关注局部地区的地质灾害发育、浅层地下空间瓦斯赋存和地下水污染等环境地质问题。区内主要地质灾害发育类型为小型滑坡,其次为崩塌和不稳定斜坡,多发生于龙泉山复背斜核部及断裂带区域,建设旅游道路和游憩设施时,要加强防范。区内局部浅层地下空间瓦斯赋存,建议在园区内进行地下工程建设时,进行超前地质预报,在施工过程中要加强瓦斯浓度监测与通风,注意火源管控。区内浅层地下水类型主要为HCO_3-Ca·Mg和HCO_3-Ca型,局部地区浅层地下水因人类活动而受到污染,其中总硬度、氨氮、氯化物等超标,建议加强公园内重点规划建设区域的地下水用途管控和生态环境保护。 相似文献
4.
邻近建筑物的暗挖隧道施工数值模拟 总被引：3，自引：0，他引：3
软土中采用暗挖法开挖隧道往往会引起土体变形,由于城市中暗挖隧道多建在建筑物高度集中的地区,土体变形对邻近既有建筑物的损伤不容忽视。采用二维有限元方法对邻近中、低层建筑物(采用整体基础)工况下的暗挖隧道施工进行了模拟和分析,建筑物长15 m。研究结果表明：建筑物的存在会增大隧道开挖引起的地面沉降和衬砌的受力与变形,同时隧道开挖也会使邻近建筑物产生附加应力和变形。当隧道轴线与建筑物轴线的水平距离 0 m时,建筑物相对安全;当 时,建筑物会产生朝向隧道一侧的倾斜。当 为2.5～20 m时,产生较大的地面沉降,建筑物的首尾沉降差较大,建筑物较危险;当 为30～40 m时,建筑物的存在对隧道施工的影响较小;当 40 m时,建筑物的存在对隧道施工的影响可以忽略不计。由于基础的存在,建筑物的最大弯矩、轴力和剪力的变化量较小,增大量在10 %以内。 相似文献
5.
S. M. S. Niknejad H. Savoji M. Pourafshari Chenar M. Soltanieh 《International Journal of Environmental Science and Technology》2017,14(2):375-384
In this work, permeation of mixed gases H2S/CH4 through commercial polyphenylene oxide (PPO) hollow fiber and poly (ester urethane) urea (PEUU) flat membranes was studied at pressures of 345–689 kPa, at ambient temperature and at 313.15 K. Various H2S concentrations of about 100–5000 ppm in CH4 binary synthetic gas mixtures as well as a real natural gas sample obtained from a gas refinery containing 0.3360 mol.% H2S (equivalent to 3360 ppm) were tested. It was observed that the permeance of components was affected by the balance between competitive sorption and plasticization effects. Separation factors of H2S/CH4 were in the range of 1.3–2.9, 1.8–3.1 and 2.2–4.3 at pressures of 345, 517 and 689 kPa, respectively. In the range of 101–5008 ppm of H2S in CH4, the effect of temperature on the separation factor was nearly negligible; however, permeances of both components of the mixtures increased with temperature. Additionally, the results obtained by PEUU membrane indicated that it was a better choice for hydrogen sulfide separation from H2S/CH4 mixtures than PPO. For PPO membrane, removal of hydrogen sulfide from high-concentration (up to 5008 ppm) binary mixtures of H2S/CH4 was compared with that of low concentration (as low as 101 ppm) through PPO. At concentrations of 101–968 ppm, plasticization was dominant compared with the competitive sorption, while for the H2S feed concentrations of 3048 ppm, the competitive sorption effect was dominant. For H2S concentration of 5008 ppm, the balance between these two effects played an important role for explanation of its trend. 相似文献
6.
针对连拱隧道复杂的施工力学特性,结合实际工程,通过模型试验和现场监测分别研究了整体式中隔墙连拱隧道在中导正洞台阶法施工过程中的位移和中隔墙应力变化情况,并详细分析了各开挖步骤对其的影响。结果表明,对于整体式中隔墙连拱隧道,上台阶开挖对顶部位移和中隔墙应力的影响大于下台阶开挖产生的影响;隧道顶点位移-历时曲线总体形状呈S形,最大位移发生在后掘隧道的顶部。由于主洞的开挖将使中隔墙另一侧应力增加较大,而本侧应力增加较小甚至降低,因此,先掘隧道的开挖使中隔墙产生由先掘隧道侧向后掘隧道侧偏转的弯矩,而后掘隧道的开挖将使该弯矩值减小 相似文献
7.
8.
The efficiency and sustainability of carbon dioxide (CO2) storage in deep geological formations crucially depends on the integrity of the overlying cap-rocks. Existing oil and gas
wells, which penetrate the formations, are potential leakage pathways. This problem has been discussed in the literature,
and a number of investigations using semi-analytical mathematical approaches have been carried out by other authors to quantify
leakage rates. The semi-analytical results are based on a number of simplifying assumptions. Thus, it is of great interest
to assess the influence of these assumptions. We use a numerical model to compare the results with those of the semi-analytical
model. Then we ease the simplifying restrictions and include more complex thermodynamic processes including sub- and supercritical
fluid properties of CO2 and non-isothermal as well as compositional effects. The aim is to set up problem-oriented benchmark examples that allow
a comparison of different modeling approaches to the problem of CO2 leakage. 相似文献
9.
Hojjat Ollah Safari Saeid Pirasteh Biswajeet Pradhan Hossein Amid 《Arabian Journal of Geosciences》2013,6(4):1101-1112
The Pisa 2 tunnel with 740 m in length and 20° N trend is located along the Kazerun fault zone in Simply Folded Belt of Zagros, Iran. This tunnel has been excavated in the fractured incompetent marl layers with high expansive pressure of up to 2 kg/cm2. In this study, the geological hazards along the tunnel have been recognized and categorized. This study revealed that, in the long-term usage of the tunnel, the lining did not endure against the loading and the secondary leakages. It is mainly attributed due to the non-efficiencies of drainage and isolation systems in the tunnel site. Therefore, it caused asphalt damage, drainage damage, and wall distortion. FLAC3D software has been used in this research. We conducted various analyses for pre-excavation stress states, syn-excavation, and post-excavation strain states. The results showed no indication of instability and critical deformations during the excavation time. It also revealed that due to the non-efficiencies of drainage and isolation systems against secondary leakages and consequently marl expansion, the volumetric and shear strains (i.e., expansions and displacements) have exceeded from the critical states of strain along the tunnel. For various remedy purpose, this paper attempted several measures that can be taken in order to modify the drainage and isolation systems along the tunnel area. The reconstruction of drainage systems with suitable reinforced concrete and adequate slope has been proposed. The width of channel and isolation of backside of lining and implementation of multi-order outlets (i.e., backside of lining) for draining of groundwater into where the main drainage systems are located in the tunnel gallery were suggested. 相似文献
10.
川藏铁路作为史上修建难度最大的铁路,沿线具有显著的地形高差、强烈的板块活动、密集的深大断裂、频发的山地灾害等恶劣地质环境特点,工程建设面临着复杂多变的地表和地下重大地质安全风险挑战。为深入综合分析川藏铁路可研阶段沿线地质风险,定量评价其对工程的影响,基于川藏铁路沿线翔实的时空数据集及资料,采用三维结构建模、数值统计建模、动力建模、时空建模等方法,进行了地表、地下重大工程地质灾害综合定量风险分析。地表工程地质灾害综合风险分析结果表明:在宏观上,川藏铁路沿线存在3个地表地质灾害高风险区,分别是鲜水河断裂带、金沙江断裂带和东构造结地区。由于川藏铁路采用以隧道为主的设计方案,地表地质灾害的风险大大降低。分别建立了活动断裂、岩爆和大变形等风险评估的普适性模型及综合风险分析模型,以易贡隧道为例,对典型重要隧道全线不同段落断裂活动性、岩爆、大变形等典型地下工程地质风险以及综合风险进行了定量评价。结果表明:川藏铁路沿线的地质灾害、断裂活动、岩爆和大变形等重大工程地质灾害的总体风险等级较高,影响工程安全;定量评估结果可以进一步指导后续的设计与施工的优化和深化。本研究为川藏铁路可行性研究提供了有力的科学支撑,同时也为国内外类似线性工程地质灾害风险分析提供参考。 相似文献
11.
Hossain Md. Shahin Teruo Nakai Kenji Ishii Toshikazu Iwata Shou Kuroi 《Acta Geotechnica》2016,11(3):679-692
To investigate the realistic ground behavior during tunneling, a new device has been developed. With the new device, model tests of tunnel excavation considering an existing tunnel and an existing building were carried out. Non-linear finite element analyses corresponding to the model tests were also conducted using FEMtij-2D software where an elastoplastic subloading t ij model was used to describe the mechanical behavior of soil. Earth pressure distribution around the tunnels and ground movements during tunnel excavation depend on the distance and position between the twin tunnels. There is a significant effect of tunneling on the existing foundation of building even in the case where the tunnel is constructed in deep underground. The numerical analyses capture well the results of the model tests. 相似文献
12.
基于对现场地质条件和开挖响应的直观认识和对岩石室内试验所得物理力学特性的深刻揭示,建立了深埋条件下软弱围岩大变形挤压程度分级方法及相对应的安全系数计算方法。该方法考虑到隧洞原岩集聚的能量过大是造成开挖后围岩失稳的根本原因,将隧洞原岩能量和围岩的总变形与弹性变形之比相结合,分析了隧洞的围岩稳定性状况,并在此基础上通过增减隧洞原岩能量得到了其安全系数。通过实际工程应用及与传统经验评价方法的对比,验证了该方法的合理性与适用性。该方法考虑了围岩的地质情况、断面形状、尺寸、开挖方式等多种因素,弥补了传统经验评价方法无法适应复杂多变的现场工程施工情况的不足,更加贴近实际。可为大变形隧洞的安全预测、开挖方案、支护设计等提供重要参考依据。 相似文献
13.
汪德云 《水文地质工程地质》2009,36(6):134-136
以南水北调中线北京段西四环暗涵工程为研究背景,通过详细分析在复杂工程环境下进行浅埋暗挖施工对既有工程环境产生的严重影响及关键控制因素,得到有效控制暗挖施工对既有环境影响的措施,如初期支护方案的勘测设计方法、施工控制监测措施、监测控制效果分析检验等。实践证明,既使是在复杂的工程环境下,地下岩土工程开挖影响也可以得到有效控制。 相似文献
14.
Gas genetic type and origin of hydrogen sulfide in the Zhongba gas field of the western Sichuan Basin, China 总被引：7，自引：0，他引：7
Guangyou Zhu Shuichang Zhang Haiping Huang Yingbo LiangShucui Meng Yuegang Li 《Applied Geochemistry》2011,26(7):1261-1273
Natural gases and associated condensate oils from the Zhongba gas field in the western Sichuan Basin, China were investigated for gas genetic types and origin of H2S by integrating gaseous and light hydrocarbon geochemistry, formation water compositions, S isotopes (δ34S) and geological data. There are two types of natural gas accumulations in the studied area. Gases from the third member of the Middle Triassic Leikoupo Formation (T2l3) are reservoired in a marine carbonate sequence and are characterized by high gas dryness, high H2S and CO2 contents, slightly heavy C isotopic values of CH4 and widely variable C isotopic values of wet gases. They are highly mature thermogenic gases mainly derived from the Permian type II kerogens mixed with a small proportion of the Triassic coal-type gases. Gases from the second member of the Upper Triassic Xujiahe Formation (T3x2) are reservoired in continental sandstones and characterized by low gas dryness, free of H2S, slightly light C isotopic values of CH4, and heavy and less variable C isotopic values of wet gases. They are coal-type gases derived from coal in the Triassic Xujiahe Formation.The H2S from the Leikoupo Formation is most likely formed by thermochemical SO4 reduction (TSR) even though other possibilities cannot be fully ruled out. The proposed TSR origin of H2S is supported by geochemical compositions and geological interpretations. The reservoir in the Leikoupo Formation is dolomite dominated carbonate that contains gypsum and anhydrite. Petroleum compounds dissolved in water react with aqueous SO4 species, which are derived from the dissolution of anhydrite. Burial history analysis reveals that from the temperature at which TSR occurred it was in the Late Jurassic to Early Cretaceous and TSR ceased due to uplift and cooling thereafter. TSR alteration is incomplete and mainly occurs in wet gas components as indicated by near constant CH4 δ13C values, wide range variations of ethane, propane and butane δ13C values, and moderately high gas dryness. The δ34S values in SO4, elemental S and H2S fall within the fractionation scope of TSR-derived H2S. High organo-S compound concentrations together with the occurrence of 2-thiaadamantanes in the T2l reservoir provide supplementary evidence for TSR related alteration. 相似文献
15.
岩爆是高地应力地区影响地下工程施工的主要地质灾害,岩爆预测已成为地下工程的世界性难题之一。地层的岩性条件和地应力的大小是影响岩爆发生的两个最根本因素,对这两个因素的准确判别将直接关系到岩爆预测的成功与否。根据工程的区域地质资料,利用FLAC3D程序建立了该区域的数值计算模型,并结合工程现场实测点的主应力数据,采用径向基函数神经网络,反演了计算区域的初始地应力场。基于现场岩石力学试验和TSP203探测技术,获取了岩爆高风险区域的地层岩性条件。最后结合地应力反演数据和TSP探测结果,对掌子面前面长距离范围内的岩爆强度进行精细预测。工程实际应用表明,该方法可操作性强,岩爆预测结果与实际开挖情况较吻合。 相似文献
16.
《International Geology Review》2012,54(3):305-326
In this article, we describe the geological features of the Ediacaran (upper Sinian), lower Cambrian and lower Silurian shale intervals in the Upper Yangtze Platform, South China, and report on the gas potential of 53 samples from these major marine shale formations. Reflected light microscopy, total organic carbon (TOC) measurement, Rock-Eval, carbon isotope ratio analysis, thermovaporization gas chromatography (Tvap-GC), and open pyrolysis gas chromatography (open py-GC) were used to characterize the organic matter. Measured TOC in this research is normally >2% and averages 5%. TOC contents are roughly positively correlated with increasing geological age, i.e. lower Silurian shales exhibit generally lower TOC contents than lower Cambrian shales, which in turn commonly have lower TOC contents than Ediacaran shales. Kerogen has evolved to the metagenesis stage, which was demonstrated by the abundant pyrobitumen on microphotographs, the high calculated vitrinite reflectance (Ro = 3%) via bitumen reflectance (Rb), as well as δ13 C of gas (methane) inclusions. Pyrolysates from Tvap-GC and open py-GC are quantitatively low and only light hydrocarbons were detected. The lower Silurian shale generally exhibits higher generation of hydrocarbon than the lower Cambrian and Ediacaran shale. Cooles’ method and Claypool’s equations were used to reconstruct the original TOC and Rock-Eval parameters of these overmature samples. Excellent original hydrocarbon generation was revealed in that the original TOC (TOCo) is between 5% and 23%, and original S1+S2 (S1o+S2o) is ranging from 29 to 215 mg HC/g rock. 相似文献
17.
Qi Li Zhishen Wu Xing-lin Lei Yutaka Murakami Takashi Satoh 《Environmental Geology》2007,51(7):1157-1164
Geological sequestration of CO2 into depleted hydrocarbon reserviors or saline aquifers presents the enormous potential to reduce greenhouse gas emission
from fossil fuels. However, it may give rise to a complicated coupling physical and chemical process. One of the processes
is the hydro-mechanical impact of CO2 injection. During the injection project, the increase of pore pressures of storing formations can induce the instability,
which finally results in a catastrophic failure of disposal sites. This paper focuses mainly on the role of CO2-saturated water in the fracturing behavior of rocks. To investigate how much the dissolved CO2 can influence the pore pressure change of rocks, acoustic emission (AE) experiments were performed on sandstone and granite
samples under triaxial conditions. The main innovation of this paper is to propose a time dependent porosity method to simulate
the abrupt failure process, which is observed in the laboratory and induced by the pore pressure change due to the volume
dilatancy of rocks, using a finite element scheme associated with two-phase characteristics. The results successfully explained
the phenomena obtained in the physical experiments. 相似文献
18.
Study on formation mechanism of gas tunnel in non-coal strata 总被引：1，自引：0，他引：1
Gases are common constituents of the underground environment, along with soils, rocks, and water. It is widely believed that gases in underground originate from the bacterial decomposition and thermal decomposition of organic and inorganic compounds, and geochemical reactions. Gases are usually widely dispersed in low concentrations, but under some geologic conditions are abundant. Gas can be a hazard to construction of underground civil works such as tunnels and underground chambers. Besides the gas tunnels in coal seam, there are a large number of tunnels with gas in non-coal strata in China, such as the Paotaishan Tunnel, Hongshiyan Tunnel, and Zengjiaping 2# Tunnel. These tunnels do not cross coal strata, but all encountered gas problems during construction. Due to lack of full understanding and thorough preparation, as well as the random non-uniform distribution of gas emission, the gas disasters in these tunnels are usually larger than the traditional ones. Study on the causes of formation has great scientific significance. This paper focuses on a variety of complete gas tunnels, summarized three types of gas tunnel in the non-coal strata, namely the structure-connected gas tunnel, including fracture, fault, and fold three subtypes according to the different geological structures; the second one is gas tunnel with metamorphic wall rock; the third is gas tunnel by composite forming causes. 相似文献
19.
采矿巷道围岩变形机制数值模拟研究 总被引：6，自引：0，他引：6
研究了大冶铁矿龙洞-62 m、-74 m水平采矿巷道开挖后的二次应力分布及巷道变形机制。首先根据现场工程地质勘查和室内岩石力学试验对巷道围岩进行了工程地质分组和岩石力学参数确定;在此基础上运用FLAC3D数值模拟软件研究了巷道开挖后的应力应变状态,分析了围岩变形机制;并根据-74 m水平采矿巷道的收敛监测数据对比验证了数值模拟结果。研究结果表明,围岩条件不同的采矿巷道其二次应力分布影响范围有所差异,但围岩主应力总体上表现为由巷道边墙中下部位的压应力集中带逐步过渡到拱顶、底板一定范围内的拉应力集中带。 相似文献
20.
S. M. Fatemi Aghda K. Ganjalipour M. Esmaeil Zadeh 《Geotechnical and Geological Engineering》2016,34(5):1487-1512
According to the International Society of Rock Mechanics, squeezing is a time dependent large deformation occurring during tunnel construction around the tunnel associated with creep caused by exceeding a limiting shear stress (Barla in ISRM News J 2:44–49, 1995). This research is conducted using a case study on the Nowsoud Tunnel, Iran. Being 14 km in length and 4.5 m in diameter, the tunnel is located in the western part of Iran near the Iraq border. Nowsoud tunnel, which was excavated using a double shield TBM, exhibited severe squeezing (with 8919 m) in its critical zone which resulted in excavation termination. In this research, the best approach for predicting squeezing among the recommended methods for reducing the damages caused by squeezing on TBM was determined. In this regard, approaches commonly used to predict squeezing are empirical, semi-empirical, and theoretical–analytical methods. Besides, these methods, numerical modeling is used to estimate convergence generated along the tunnel pathways, which is ultimately used to categorize squeezing. This paper compares squeezing prediction methods in 68 section of Nowsoud Tunnel. These 68 sections indicate that the empirical methods propose a general estimation/overview of squeezing. Among the semi-analytical approaches, the one proposed by Hoek and Marinos (Rock engineering in difficult rock conditions—soft rocks and karst, Taylor & Francis Group, London, pp 49–60, 2000) are compatible with the occurrence of squeezing in the critical zone. However, the degree of predicted squeezing is less than the real degree of squeezing in this zone. Based on the result of Aydan approach, 75 % of the tunnel sections are under squeezing condition. Theoretical–analytical approaches underestimate the possibility of squeezing in the critical zone. Barla?s approach (1995) demonstrated the possibility of squeezing in the critical zone with low intensity. The numerical computations in this paper were performed using Plaxis (version 8.5), a two-dimensional numerical program based on the finite element method. Plaxis results, classified by Hoek and Marinos (2000) method, show that 8800 m of the tunnel length is under the non-squeezing condition. According to all prediction methods, the squeezing zones depend on faulted zones, argillaceous limestone and shale formations such as J1Kh, J4Kh, J5Kh, and Kgr. These formations were identified with a high quantity of shale and argillaceous limestone. Bedding of these geological formations is thin and their geotechnical properties are weaker than those of limestone formations. On the other hand, non-squeezing zones depend on limestone formations such as J2Kh, J3Kh, J6Kh, Kabg, and Kbg. Moreover, all approaches predicted squeezing potential for the critical zone where TBM is jammed. 相似文献