Estimation of Rock Mass Equivalent Permeability Around Tunnel Route Using the Geostatistical Methods: A Case Study

IF 1.7 4区 工程技术 Q3 ENGINEERING, CIVIL
Sanaz Khoubani, Ali Aalianvari, Saeed Soltani-Mohammadi
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Abstract

The objective of this paper is to estimate the equivalent permeability of the rock surrounding the tailrace tunnel of the Azad Dam pumped storage power plant, using geostatistical methods. The permeability of the rock mass is a critical factor that influences the estimation of water flow rates. Since the tunnel passes through various geological units with different permeabilities, it is crucial to estimate the equivalent permeability for each unit in order to predict the water seepage from that unit into the tunnel. In order to estimate the permeability along the tunnel and underground structures, twelve exploratory boreholes were drilled, and water pressure tests were conducted. Due to the distribution of the exploratory boreholes, a study and statistical analysis are necessary to determine the permeability of the rock mass for each geological unit. Using geostatistical log kriging, multiple indicator kriging with four thresholds, and multiple indicator kriging with five thresholds, the permeability of the rock mass at the tunnel route was estimated. The results indicate that at least 40% of the rock mass has low permeability, while the remaining mass of the tunnel passes through rocks with moderate to high permeability. The accuracy of the estimated permeability values was evaluated by predicting the water inflow into the tunnel using the estimated permeability values and comparing it to the observed flow. Numerical models were generated for each geological unit to estimate the water inflow into the tunnel, based on the results of the geostatistical methods. Log kriging, multiple indicator kriging with four thresholds, and multiple indicator kriging with five thresholds were used to calculate the water inflow, resulting in 94.15, 94.15, and 127.5 L per second, respectively. The results of the modeling were compared to the observed water flow into the tunnel. Comparing the modeling results to both the statistical methods and observed values showed errors of 31.2%, 31.2%, and 6.9%, respectively. Of the three methods, the multiple indicator kriging computational method with five thresholds was found to be the most accurate, with the least amount of error and the closest approximation to the actual value. As a result, it was selected as the best method.

Abstract Image

利用地质统计方法估算隧道路线周围的岩体等效渗透率:案例研究
本文旨在利用地质统计方法估算阿扎德大坝抽水蓄能电站尾水隧道周围岩石的等效渗透率。岩体的渗透性是影响水流量估算的关键因素。由于隧道穿过不同渗透率的地质单元,因此必须估算每个单元的等效渗透率,以预测从该单元渗入隧道的水量。为了估算隧道和地下结构沿线的渗透率,我们钻探了 12 个探孔,并进行了水压试验。由于勘探钻孔的分布,有必要进行研究和统计分析,以确定每个地质单元岩体的渗透性。利用地质统计日志克里格法、带四个阈值的多指标克里格法和带五个阈值的多指标克里格法,对隧道路线岩体的渗透率进行了估算。结果表明,至少有 40% 的岩体具有低渗透性,而隧道的其余岩体则穿过具有中等至高渗透性的岩石。通过使用估算的渗透率值预测流入隧道的水量,并将其与观测到的水流进行比较,评估了估算渗透率值的准确性。根据地质统计方法的结果,为每个地质单元生成了数值模型,以估算流入隧道的水量。采用对数克里金法、四阈值多指标克里金法和五阈值多指标克里金法计算流入水量,结果分别为每秒 94.15 升、94.15 升和 127.5 升。模拟结果与观测到的隧道水流量进行了比较。将建模结果与统计方法和观测值相比,误差分别为 31.2%、31.2% 和 6.9%。在这三种方法中,采用五个阈值的多指标克里金计算方法被认为是最准确的,误差最小,最接近实际值。因此,该方法被选为最佳方法。
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来源期刊
CiteScore
3.30
自引率
11.80%
发文量
203
期刊介绍: The aim of the Iranian Journal of Science and Technology is to foster the growth of scientific research among Iranian engineers and scientists and to provide a medium by means of which the fruits of these researches may be brought to the attention of the world’s civil Engineering communities. This transaction focuses on all aspects of Civil Engineering and will accept the original research contributions (previously unpublished) from all areas of established engineering disciplines. The papers may be theoretical, experimental or both. The journal publishes original papers within the broad field of civil engineering which include, but are not limited to, the following: -Structural engineering- Earthquake engineering- Concrete engineering- Construction management- Steel structures- Engineering mechanics- Water resources engineering- Hydraulic engineering- Hydraulic structures- Environmental engineering- Soil mechanics- Foundation engineering- Geotechnical engineering- Transportation engineering- Surveying and geomatics.
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