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1.
为提高方形抗滑桩开挖成孔效率,研究适用于复杂条件岩质滑坡抗滑桩快速成孔的工艺,以成都东部某大型岩质滑坡101根大截面抗滑桩为对象,通过现场调查、理论分析及工程试验等方法,研究了方形抗滑桩工程成孔工艺、施工特征和不同地层成孔工艺适用体系。研究表明,研制的“旋挖钻孔+人工辅助清边”成孔工艺作业效率大大提高,在该抗滑桩工程中实施达到日平均进尺2.0 m高效率,顺利达到工期要求,进而解决了岩石成孔效率慢、工艺落后的问题;根据滑坡所处条件选择合适的施工工艺对抢险救灾工程至关重要,对于交通条件好、工期要求高的大型滑坡治理工程,优先考虑“旋挖钻孔+人工辅助清边”工艺;对于交通条件差、作业受限的小型滑坡治理工程,采用风镐开挖土体、水磨钻开挖岩石成孔工艺。 相似文献
2.
Tunnel water inrush disaster is a serious problem in karst tunnel construction and occurs extensively in southwestern China. To prevent water inrush, hydraulic lining has been utilized extensively in karst tunnel construction. The failure of the hydraulic lining in the Tongxi tunnel is an example of a typical failure case that has yet to be fully analyzed. In this paper, the failure of the waterproof liner was studied by theoretical and numerical methods. By field investigation, the failure of the tunnel lining was attributed to a high hydraulic pressure head converging in the large karst caves behind the lining. The corresponding mechanical model can be simplified as a “karst cave water pressure” model. The key to the mechanical model was to determine the water pressure of the karst caves produced by the lining. The variation in water pressure was directly related to the cave’ reservoir volume, catchment flow and catchment time. Thus, volume calculation formulas for two types of karst caves (strike and oblique caves) in the studied tunnel were constructed based on the engineering geological conditions. Considering the precipitation, the flow rate in the karst caves was regarded as nearly constant during the catchment period. Hence, reservoir volumes during different periods can be calculated and converted to the stress boundary conditions of the lining. Then, the mechanical response of the tunnel under different water levels was calculated by numerical simulation. Combining the field investigation and monitoring data, the tunnel lining failure was mainly believed to be triggered by hydraulic fracturing failure due to a high-pressure head. Finally, prevention measures were proposed based on the results of this study. 相似文献
3.
Earthwork and surface excavation activities play an important role in construction projects. Selecting the best technique to loosen the overburden material within the surface excavation in open mining and geotechnical projects is of great importance from economical and technical viewpoints. Surface excavation includes direct digging, ripping and blasting. To select the most effective method and plan for excavation, geotechnical investigation is very important. It is also a big help in avoiding conflict between contractors and clients when they do not reach mutual agreement regarding the price of rock and soil excavation. There are many engineering classification systems used to assess rock masses for excavation purposes. All of these systems consider several geotechnical parameters to assess the earth masses. This study reviews these systems and then offers a new categorization based on the Rock Mass index (RMi) classification system and block volume to assess excavation in rock masses. The original dataset was obtained from the literature review as well as the surface excavation in Upper Gotvand dam and Hydro Power Plant (HPP). The offered system was also validated through the data extracted from the surface excavation in Sardasht dam and HPP in Iran. 相似文献
4.
岩溶塌陷的产生会严重影响隧道的安全施工及运营,而隧道的开挖又加剧了岩溶塌陷发生的可能性,并使其发生机制变的更加复杂。本文选择隧道埋深、隧道涌水量及距离隧道的远近3个因素来衡量隧道开挖对岩溶塌陷的影响。并以长基岭隧道为例,运用模糊数学理论结合层次分析法,选择了包括隧道埋深、涌水量等在内的14个因素,建立研究区岩溶塌陷模糊综合评判模型,并通过程序与GIS集成实现了研究区岩溶塌陷危险性分区。评价结果对岩溶地区隧道的施工及运营提供依据。 相似文献
5.
One of the most important steps in designing underground structures is the evaluation of ground conditions in terms of squeezing potential and behavior of the geological structures. Generally, constructing a tunnel in the squeezing condition is a very slow and difficult task. Therefore, recognition and evaluation of the squeezing potential is very important in selecting a suitable excavation method and support, especially in weak rocks. This research is concerned with the assessment of squeezing potential along tunnel T4 of water conveyance system from Azad dam to Ravansar plain with the length of 11,380 m, located between Kurdistan and Kermanshah provinces, west of Iran. This tunnel is in an almost NS direction and flows through the contact zone of Iran and Arabic plates. According to the engineering geological investigations, the squeezing potential has been recognized as the most important difficulty in the excavation of tunnel T4. This conclusion can be explained by the several indicators including lithology, high disintegration of rock masses, alteration of rocks on the border of Iran and Arabic plates’ contact zone, low rock mass quality, high overburden, and highly jointed rock masses in a shuffle tectonic condition. This paper deals with the engineering geological and geomechanical properties of rock masses. Then, it evaluates squeezing intensity using empirical, semi-empirical, and analytical properties methods. The analysis conducted in these work shows that the tunnel excavation would encounter squeezing problems, which is most severe in region 2 due to the effects of the major young Zagros fault. 相似文献
6.
Excavation-induced ground movements and the resulting damages to adjacent structures and facilities is a source of concern for excavation projects in urban areas. The concern will be even higher if the adjacent structure is old or has low strength parameters like masonry building. Frame distortion and crack generation are predictors of building damage resulted from excavation-induced ground movements, which pose challenges to projects involving excavations. This study is aimed to investigate the relation between excavation-induced ground movements and damage probability of buildings in excavation affected distance. The main focus of this paper is on masonry buildings and excavations stabilized using soil nail wall method. To achieve this purpose, 21 masonry buildings adjacent to 12 excavation projects were studied. Parametric studies were performed by developing 3D FE models of brick walls and excavations stabilized using soil nail wall. Finally, probability evaluations were conducted to analyze the outputs obtained from case studies. Based on the obtained results, simple charts were established to estimate the damage of masonry structures in excavation affected distance with two key parameters including “Displacement Ratio” and “Normalized Distance”. The results also highlight the effects of building distance from excavation wall on its damage probability. 相似文献
7.
拱北隧道暗挖段作为港珠澳大桥珠海连接线的重点工程,首次运用管幕冻结法进行施工。该法综合管幕法和人工地层冻结法的优势,可在隧道断面形成“顶管?冻土帷幕”复合支护体系,有效实现“承载”与“顶管间止水”的双重目标,确保隧道开挖时的稳定与安全。为获得“顶管?冻土”复合结构的温度、变形与力学特性,基于相似理论自主研发构建一套相似模型试验系统并开展试验研究,同时利用有限元软件COMSOL Multiphysics建立数值计算模型进行模拟验证。结果表明:复合结构的冻结温度场因空、实顶管及其内部冻结器的布置形式呈现不均匀分布特征,冻土形成速率在冻结后期明显变缓;土体竖向冻胀变形在60~160 min内急剧增大,且冻胀量随深度增加而增大,整体规律与温度场分布密切相关;土体冻结产生的冻胀力对顶管水平受力影响较大,空顶管相对刚度较小而产生较大水平变形;在加载阶段,顶管受力与变形均以竖向为主。因空、实顶管刚度差异和冻土厚度不均匀的共同影响,空顶管竖向变形包含了“弯曲”与“压扁”并具有非线性特征,其跨中截面底部竖向位移峰值约为实顶管的1.6倍;加载至0.28 MPa时,管间冻土首先发生破坏,进而导致顶管间封水功能失效,实际施工中应重点监测空顶管的变形规律、管间冻土帷幕的温度变化及其完整性。研究成果可为管幕冻结法的施工与监测提供参考,也可为热力耦合数值计算模型提供验证依据。 相似文献
8.
Net present value (NPV) is the most popular economic indicator in evaluation of the investment projects. For the mining projects, this criterion is calculated under uncertainty associated with the relevant parameters of say commodity price, discount rate, etc. Accurate prediction of the NPV is a quite difficult process. This paper mainly deals with the development of a new model to predict NPV using artificial neural network (ANN) in the Zarshuran gold mine, Iran. Gold price (as the main product), silver price (as the byproduct), and discount rate were considered as input parameters for the ANN model. To reach an optimum architecture, different types of networks were examined on the basis of a trial and error mechanism. A neural network with architecture 3-15-10-1 and root mean square error of 0.092 is found to be optimum. Prediction capability of the proposed model was examined through computing determination coefficient ( R 2?=?0.987) between predicted and real NPVs. Absolute error of US$0.1 million and relative error of 1.4 % also confirmed powerfulness of the developed ANN model. According to sensitivity analysis, it was observed that the gold price is the most effective and discount rate is the least effective parameter on the NPV. 相似文献
9.
Liquefaction potential (LP) assessment plays a significant role in damages due to earthquake. The spirit underlying the present work is the evaluation of LP by correlating most significant parameters reflecting the dynamic response of soil with actual field behavior wherein an attempt of integrating the effect of dynamic soil properties and ground motion parameters simulating the actual site conditions is being made. Accordingly, a dynamic response–based Elementary Empirical Liquefaction Model (EELM) is proposed by processing a total of 314 reported case records covering a wide range of parameters demarcating “yes” and “no” zones of liquefaction. The method to develop the EELM essentially consists of evaluation of liquefaction potential, defining functional form of EELM representing dynamic response of soil to earthquake shaking, collection of data, computation of model parameters and formulation followed by validation of the model. The proposed empirical model though in fundamental form is found to perform fairly well resulting into an overall success rate of 86 % for both liquefaction and non-liquefaction points with significantly high success rate of 98 % for liquefied cases. Comparison of predictive performance of the proposed EELM with other approaches shows higher efficiency and thus signifies the theme of employing integrated approach. 相似文献
10.
In recent decades, the high population growth has increased the demand for agricultural lands and products. Groundwater offers reliability and flexibility in access to water for irrigation purposes, especially in arid and semi-arid areas, such as Amol-Babol Plain, Iran. However, the quality and quantity of groundwater may not be suitable for irrigation purposes in all areas due to urbanizations, and intensive agricultural and industrial activities. Groundwater suitability zoning for irrigation purposes could be useful to improve water resources and land use planning, mostly in areas with water scarcity. Therefore, a GIS-based indices method is proposed to assess suitable zones for agricultural activities, integrating the irrigation water quality (IWQ) index and hydrogeological factors. IWQ index was utilized to assess groundwater quality based on salinity hazard, infiltration hazard, specific ions, and trace elements hazards, and miscellaneous effects such as pH, bicarbonate, and nitrate. The potential of the aquifer for irrigation water abstraction was investigated using hydrogeological surveys such as slope angle of the plain, hydraulic conductivity, and aquifer thickness. The groundwater suitability index classified most of the study area (more than 90 %) as “excellent” or “good” suitability zones for irrigation purposes. A limited area of around 5.6 % of the total area has moderate suitability for irrigation purposes due to the Caspian Seawater intrusion and the presence of fossil saline water. The proposed methodology provides useful information in order to allow irrigation management to prevent water and soil deterioration. 相似文献
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