共查询到20条相似文献，搜索用时 31 毫秒
1.
钻孔灌注桩后压浆后,与坑外含水层相比,基坑范围内含水层的渗透系数减小,这对基坑降水渗流场具有比较明显的影响。某广场式建筑由五幢塔楼和地下车库组成,采用桩侧后压浆钻孔灌注桩,基坑开挖深度21m,承压含水层组厚10m,透水性较强,采用敞开式完整井降水,井位主要沿基坑周边布置。在对水文地质条件进行概化后,建立了地下水三维非稳定流数值模型,进行了非均质渗流场模拟,并与均质渗流场作比较。结果表明,坑内后压浆区域的渗透系数减小后,坑内水力坡度变陡,单井涌水量减小,井数应相应增加;若模型计算域全部按注浆后的渗透系数考虑,则会严重降低补给强度、低估基坑总涌水量;在相同的降深要求下,坑内后压浆后渗透系数减小、但坑外渗透系数不变,基坑总补给量基本没有变化。现场监测与模拟结果较为一致。研究成果对类似工程地下水控制有一定的借鉴意义。 相似文献
2.
将降水工程抽取的地下水进行资源性回灌是高渗透性富水地层地下水控制中保护地下水资源的一种有效选择。当回灌场地受限离降水影响区域不够远时,降水与回灌可能存在耦合作用。基于潜水完整降水-回灌井群的浸润线方程,建立了一体化降水回灌井点群系统等流量近似理论解和等效大井近似理论解公式,并进行了误差分析。以北京某基坑工程为例,一体化降水回灌工程的近似理论解、数模分析、流量实测三者结果能互相符合,验证了公式的可靠性。给出了应用公式进行场地受限条件下一体化降水回灌设计问题的求解思路、求解步骤,建立了潜水完整井的一体化降水回灌设计方法。 相似文献
3.
基坑降水的成功与否,关系到整个基坑的安全。南通市南山湖综合楼基坑开挖过程中虽建立了止水帷幕,但仍需对基坑降水的方案进行安全评估。采用MIDAS/GTS数值分析软件建立三维渗流模型,通过对现场单井抽水试验进行模拟分析,综合地勘报告中室内试验渗透系数和抽水试验的渗透系数,反向推演出符合工程实际的渗流边界函数和渗透系数;然后利用反推得到的计算参数,建立三维渗流模型,模拟群井抽水状态下水位降深与时间的变化关系,对群井降水效果进行分析,验证降水井设计是否合理,指导基坑土方的开挖。 相似文献
4.
深厚强透水含水层超大基坑降水群井效应研究 总被引：1，自引：0，他引：1
基坑减压降水的幅度与群井效应密切相关。某超大面积基坑,含水层组厚40m,中下部透水性强,采用非完整井降水。对水文地质条件概化,建立了地下水三维非稳定流数值模型,对均匀布置群井、不均匀布置群井、分块开挖降水、不同的井结构、布设回灌井等工况,进行了渗流场模拟。研究表明,强透水性含水层超大面积基坑降水的群井效应极为明显;井位角密中疏布置,可实现降深调平,避免降深不足和超降;基坑分块降水,可减少坑外降深;短滤管井结构可减少基坑总涌水量和坑外降深;强透水性含水层可灌性强,回灌对减少坑外水位下降有较明显的效果。模拟结果与现场监测较为一致。研究成果可为类似工程地下水控制设计提供参考。 相似文献
5.
基坑降水的成功与否,将对基坑开挖和周边环境产生重要影响,因此有必要对基坑降水方案进行评估。针对扬中金源时代购物中心基坑降水问题,采用MIDAS/GTS对基坑降水效果进行研究。首先,依据地勘报告中提供的土体渗透系数,结合单井、双井抽水试验结果,反演出MIDAS/GTS中需要的土层渗流系数和边界函数;然后利用反演得到的参数,建立了考虑回灌井补水效应的三维基坑降水效果分析模型,模拟基坑内水位降深与时间的变化关系,并对基坑降水效果进行分析和评估,以期指导土方开挖工程的施工。 相似文献
6.
压实黄土非饱和渗透系数试验研究 总被引：2，自引：0，他引：2
压实黄土非饱和渗透特性具有重要的工程意义。对不同干密度的压实黄土试样,采用非饱和导水率测定系统进行非饱和渗透系数量测,得到不同干密度压实黄土的渗透系数与吸力的关系。试验结果表明：渗透系数随吸力的增大而成非线性减小,随干密度的减小而增大;在低吸力时,干密度对渗透系数的影响较大;在较高吸力时,干密度对渗透系数的影响较小。进一步给出了压实黄土的渗透系数模型并进行回归分析,得到各Wind幂函数模型参数与干密度的关系,建立了基于干密度的压实黄土渗透系数的确定方法。 相似文献
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8.
Z. Yarmohammadtooski A. Salmachi A. White M. Rajabi 《Australian Journal of Earth Sciences》2017,64(3):319-333
Fluid flow characteristics of cleat systems in coalbed methane reservoirs are crucial in reservoir management and field development plans. This paper aims to evaluate the cleat system properties including cleat porosity, permeability, and aperture as well as the impact of permeability growth on production performance in the Bandanna Coal Formation of the Fairview Field, eastern Queensland. Owing to the presence of bad hole conditions and poor core recovery of the coal intervals, the petrophysical well logs and laboratory measurements cannot be used as a source of information for this purpose. Hence, a new approach is employed that utilises early water production data to measure water in place and absolute permeability of the coal. In addition, micro-computed tomography (CT) scan method is used to investigate the cleat system that is preserved in a core sample and results are compared with the ones obtained by analysis of production data. Cleat system evaluation by analysis of production data and micro-CT scan technique provides a comprehensive approach that brings confidence in measurements and helps to obtain cleat properties at the sufficient scale for reservoir engineering purposes. The necessary information including production data and core samples are collected from a dewatering well and the nearby observation well in the study area. Analysis of early water production data (single-phase flow) indicates that coal permeability is 189 mD and the average cleat porosity is approximately 5%. High cleat porosity describes the large volume of water produced over the life of the study well. The 3D model of the fossilised cleat system constructed by the micro-CT scan method reveals that coal is well-cleated and cleat spacing and mean cleat aperture are 4 and 0.136 mm, respectively. The average cleat porosity that is measured by the micro-CT scan method is 5.7%, which is fairly close to the cleat porosity measured by analysis of production data. Production data analysis indicates that effective permeability to gas starts to grow at the midlife of the well and it strongly controls the shape of the production profile. The results of this study help in future field development and infill drilling programs in the Fairview Field and provide important insights into cleat system of Bandanna Coal Formation. 相似文献
9.
A review of some tracer-test design equations for tracer-mass estimation and sample-collection frequency 总被引：2，自引：0，他引：2
Malcolm S. Field 《Environmental Geology》2003,43(8):867-881
Determination of necessary tracer mass, initial sample-collection time, and subsequent sample-collection frequency are the three most difficult aspects to estimate for a proposed tracer test prior to conducting the tracer test. To facilitate tracer-mass estimation, 33 mass-estimation equations have been developed over the past century. These 33 equations are reviewed here, 32 of which were evaluated using previously published tracer-test design examination parameters. Comparison of the results produced a wide range of estimated tracer mass, but no means is available by which one equation may be reasonably selected over the others. Each equation produces a simple approximation for tracer mass. Most of the equations are based primarily on estimates or measurements of discharge, transport distance, and suspected transport times. Although the basic field parameters commonly employed are appropriate for estimating tracer mass, the 33 equations are problematic in that they were all probably based on the original developers experience in a particular field area and not necessarily on measured hydraulic parameters or solute-transport theory. Suggested sampling frequencies are typically based primarily on probable transport distance, but with little regard to expected travel times. This too is problematic in that tracer sampling remains a haphazard process that tends to result in false negatives or data aliasing. Simulations from the recently developed efficient hydrologic tracer-test design methodology (EHTD) were compared with those obtained from 32 of the 33 published tracer-mass estimation equations and suggested sampling frequencies. EHTD applies functional relationships developed from hydrologic measurements in a solute-transport model to develop a preliminary tracer-breakthrough curve that has been shown to reasonably predict actual tracer-test results. 相似文献
10.
淮南矿区地应力条件及其对煤层顶底板稳定性的影响 总被引：4，自引：1，他引：3
通过现场地应力测量和理论分析以及数值模拟计算,研究了淮南矿区地应力分布规律,探讨了圆形硐室围岩应力分布和不同侧压下回采工作面顶板稳定性分布。研究结果表明:淮南矿区原岩应力主要表现为自重应力场,除局部构造应力集中外,不存在高构造应力;区内侧压力系数λ值一般为0.49~1.49,平均为0.92,并且与测点距地表深度有一定的趋向性,表现为在浅部λ值较大,变化范围也大,而在深部λ值渐小,变化范围也缩小;回采工作面顶底板稳定性与侧压系数λ的大小密切相关,且随侧压系数λ的增大,顶板垂直位移减小,顶板岩层易于形成结构平衡而保持稳定,但底板垂直位移量增大,且易于形成底鼓破坏。这些认识为研究区煤层顶底板岩层支护控制提供了科学依据。 相似文献
11.
涌漏点的存在使得落底式止水帷幕条件下基坑涌水量的计算成为一个有待解决的技术难题。在承压含水层中开挖落底式深基坑时,针对落底式止水帷幕渗漏的不确定性,建立承压含水层中落底式基坑非完整井降水水文地质模型。基于Theis非完整井非稳定流理论,结合映射原理,推导等效渗透系数计算公式,并提出涌漏系数法用以评价落底式止水帷幕隔渗效果以及计算基坑涌水量。以武汉某深基坑降水工程为例,采用该方法评价止水帷幕的隔渗效果以及对其基坑涌水量进行计算,并与实测结果和传统方法计算结果分别进行对比验证。结果显示涌漏系数法计算误差较小,且计算过程简便,兼具安全性和经济性。研究结果可应用于指导工程设计,具有一定实际应用价值。 相似文献
12.
大型地下水封石油洞库渗流场时空演化特征研究 总被引：1，自引：0，他引：1
地下水封石油洞库是利用饱水岩体密封性进行石油储存的方式。在地下水封石油洞库的建设中,由于工程体的出现,改变了区域地下水的补给、径流和排泄条件,干扰了原来平衡的地下水渗流场,为保证地下石油洞库的水封效果,需进行裂隙岩体渗透特性及地下水渗流场时空演化研究。以国内首个在建的大型地下水封石油储库为工程背景,结合现场试验数据分析,运用等效连续介质的方法,采用裂隙岩体各向异性渗透张量,建立三维地下水数值模拟模型,预测不同施工进程时地下水位的变化。分析预测结果表明：在地下洞室开挖过程中,无水幕条件下地下水位逐渐降低,主洞室部分区域出现零水头压力区,无法保证水封性;模拟运营期水幕巷道施加定水压力,地下水位上升至设计高度35 m且趋于稳定,可以满足水封效果要求。研究结果对地下石油洞库的水封性评价具有一定的工程意义和理论价值。 相似文献
13.
The problem of predicting dependence of constant pressure batch dewatering of particulate suspensions on feed solids concentration is considered. Scaling transformations which demonstrate that evolution in the cake consolidation stage of dewatering is governed by an underlying self-similar behavior are proposed. The self-similar master curve, which can be obtained using only one set of experimental dewatering data obtained with a feed suspension having solids concentration above the gel point, is employed for estimating dependence of key dewatering process parameters on feed solids concentration. Using the parameter estimates in a Darcy's law based dewatering model, it is shown that the complete evolution of dewatering for a desired feed solids concentration can be predicted with reasonable accuracy. The approach is simpler to implement in comparison to available pressure filtration models, which require several suspension characterization experiments. 相似文献
14.
裂隙岩体的渗透特性受控于裂隙的发育特征、连通特性和充填情况,并与岩体的地应力水平具有显著的相关性。基于裂隙岩体渗透性的影响因素,并考虑现有渗透系数估算模型的不足,利用钻孔压水试验和钻孔电视图像资料,建立考虑埋深(Z)、岩石质量指标(RQD)以及充填物指标(FSD)等3个指标的渗透系数估算ZRF模型,并应用到牙根二级水电站及其他工程区的渗透系数估算中。结果表明,与已有的渗透系数估算模型相比,ZRF模型较好地反映了岩体渗透性的影响因素,且模型参数物理意义明确,便于获取,对分析裂隙岩体渗透性具有一定的工程参考价值。 相似文献
15.
介绍了磁西超千米井筒设计和地质条件,展示了井壁受力的实测方案以及依据包神解析公式进行地层原岩应力反演计算的原理。实测结果反演得到了井筒1 208 m深处的水平应力平均估值以及不均匀分布情况,水平应力与垂直应力之比符合自重应力场的规律,侧压力系数估值约为0.256~0.278之间。通过有限元数值模拟,图形化展示了井筒地应力分布,验证了实测反演数据的合理性,同时也反映了岩层剪切模量和构造等地质条件对水平应力不均匀分布的影响规律。结合对该矿区宏观地质构造运动演化和地质力学的定性分析原理,综合地分析了实测结果、解析反演和数值计算之间的一致性,对水平原岩应力Hoek & Brown统计规律的普适性提出了质疑,讨论了现有原岩应力解析计算方法,为采用包神公式进行井壁设计供了参考。 相似文献
16.
为准确获取原状Q3黄土的竖向和水平饱和渗透系数,进行了原位、室内试验测试以及数值模拟反演,并应用大型试坑浸水试验检验了所获饱和渗透系数的可靠性。进行了不同内径尺寸的原位双环入渗试验,获取了竖向饱和渗透系数,并应用室内试验测试了竖向和水平饱和渗透系数以及持水曲线;应用COMSOL软件对双环入渗试验进行数值模拟,检验了所测饱和渗透系数的可靠性,利用正交试验获得了最优的竖向和水平饱和渗透系数取值,并利用反演结果对试坑进行数值模拟,将其水分入渗情况与实测值对比。研究结果表明：在现场进行双环入渗试验时选取较大内径的双环获得的竖向饱和渗透系数更为合理。针对双环入渗试验,数值模拟反演所得最优饱和渗透系数在竖向上接近于原位试验所得竖向饱和渗透系数、水平向上接近室内所测水平向饱和渗透系数,竖向饱和渗透系数比水平向饱和渗透系数更加显著地影响水分入渗过程。通过对大型试坑水分入渗情况的验证,检验了反演所得最优饱和渗透系数的可靠性。 相似文献
17.
渗透系数决定了深基坑工程涌水量的估算及止水帷幕的型式,影响工程安全及造价,对富水地区深基坑工程建设具有重大的意义。对于非均质含水层组,现有的解析公式中,很难找到合适的方法计算水文地质参数,特别是垂直方向的渗透系数。通过在现场施作临时止水帷幕,利用帷幕的绕流阻水作用进行抽水试验,模拟基坑开挖过程中的降水问题,再建立水文地质概念模型和地下水流数学模型,并利用三维有限差分数值模拟软件反演出各层渗透系数,最后通过验证性抽水资料对模型进行了验证,为福州一临江巨厚砂卵石地层地铁车站的围护结构设计中地下水控制提供了设计参数。该试验和数值模拟结果可为类似工程参考。 相似文献
18.
Abouzar Sadrekarimi 《Geotechnical and Geological Engineering》2016,34(4):1135-1154
Static liquefaction failure of a sloping ground occurs when the shear stress applied by a monotonic triggering load exceeds the undrained yield (peak) shear strength of the saturated liquefiable cohesionless soil. Current practices for determining the in-situ undrained yield strength for ground subject to static shear stress either rely on a suite of costly laboratory tests on undisturbed field samples or empirical correlations based on in-situ penetration tests which do not account for the effects of anisotropic consolidation, intermediate principal stress, and mode of shear on the degree of strain-softening and brittleness of cohesionless soils. This study investigates the effects of variations in the direction and relative magnitudes of principal stresses associated with different modes of shear and ground slopes on static liquefaction failure of cohesionless soils. Empirical relationships are developed between soil brittleness index and maximum excess pore water pressure ratio to characterize soil shearing behavior observed in a database of 271 undrained laboratory shear tests collected from the past literature. The application of these relationships for estimating the static liquefaction triggering strength of cohesionless soils under sloping grounds is described for plane-strain boundary conditions and the results are compared with those back-calculated for several cases of static liquefaction flow failures. The proposed procedure incorporates variations in mode of shear and initial stress anisotropy in an empirical formulation based on in-situ penetration tests. 相似文献
19.
基坑工程中,通常采用地下水回灌措施降低降水对周边地质环境产生的不良影响,然而目前基坑降水—回灌的相关设计理论仍处于探索阶段。本文通过引入平面二维流势函数理论和叠加原理,分别求解得到了无止水帷幕工况下潜水完整井和承压完整井在降水—回灌共同作用下的地下水浸润曲线方程;此外,本文通过空间汇点原理和镜像原理分别求得基坑内降水和基坑外回灌对基坑外地下水位的影响,并运用叠加原理得到了有止水帷幕工况下,深基坑降水—回灌作用下的地下水浸润曲线解析式。本文利用得到的解析式探讨了在具有止水帷幕条件下回灌井距基坑围护结构的距离、渗透系数等主要因素对浸润曲线的影响,为基坑降水—回灌设计提供了参考依据。 相似文献
20.
The compressed air energy storage(CAES) is a much-awaited new system for load leveling power supply. An economical system must be developed, preventing leakage of stored air (with pressures of more than 20 atm) using groundwater pressure surrounding an unlined cavern in hard rock. The air tightness of the rock around the cavern must be confirmed. In this study, the hydrogeology of the test site was examined prior to field air tightness tests in the borehole. The results indicate that, when evaluating the hydrogeology of the test site related to the air tightness of rocks, it is necessary to understand the geological structure and fracture characteristics of the site. This is done by means of a field survey, investigations and tests in and between the boreholes, and the examination of the distribution of permeability and pore water pressures. 相似文献