IRANIAN JOURNAL OF MINING ENGINEERING (IRJME)
Year:2010 | Volume:5 | Issue:9|Papers Count:11

Line 2 Tehran Subway Tunnel has been excavated by a special designed TBM with an open face shield. Then the prefabricated reinforced segmental concrete lining, type (8+1), has been erected as a permanent support system.Subsequently, cementitious grout was used to create a peripheral water sealing curtain to prevent inrush water into the tunnel. In this paper, the effort has been made to deeply investigate the principles and technology employed in grouting of and improving the alluvial deposits surrounding Line 2 Tehran Subway Tunnel. Hence, the results obtained from laboratory tests along with in-situ water pressure tests (WPT) were used to evaluate the influence of grouts on strength characteristic of the in-situ alluvial deposits. The results revealed considerable changes due to cementitious grouts in decreasing permeability and displacement, and the increase in strength characteristics of the surrounding alluvial deposits as well.Furthermore, for the first time, also in this paper, the grouted soil samples were used to analyze the grout distribution within the samples visually. The results were also used to establish an empirical relation within the parameters involved. Hence, an empirical equation has been proposed by which the percentage of quality of grouted soils can be estimated.

Several stages of crushing and grinding are replaced by Autogenous mills in comminution circuits. The performance of these mills are affected by several operational parameters and feed size distribution. In this research, comminution experiments including; impact, abrasion and self-breakage, on fresh feed samples of Choghart AG mill, were carried out. The values of impact breakage and selection functions, abrasion parameters and self-breakage model on representative samples were determined. The mean retention time of Choghart AG mill was also measured. Using the data of the plant and the results of experiments, the Choghart AG mill was simulated by MODSIM software. The product size distribution of Choghart AG mill predicted by the software was in good agreements with the measured data. This technique was used to evaluate the effect of operational parameters on the mill performance.

The gold mineralization in Kurdistan Province of Iran was classified as shear zone gold type by some of the researchers. In the current study, the geochemical samples collected from the secondary environment, stream sediments, at the SW of Saqquez area were used to investigate the geochemical characteristics of the gold mineralized zones in this environment. The multi-variant statistical analysis, cluster analysis, was used to identify the gold paragenesis. The cluster analysis was led to identify the geochemical paragenesis of Au, which is W, Bi, Sn, and Hg. Hg, and Sb haloes are extended in un-mineralized area. As element, which is an important paragenesis in many gold deposits, was used instead of Hg in this investigation. The anomaly areas for each element were determined based on the probability plot modeling method. The spatial dispersion haloes of the anomaly areas, as 2D map, were identified based on the modeling of probability plot results. The results of interpretations were shown that Sn, W and Bi were highly correlated with Au in the study area. Element of as did not show an important correlation and anomalous area in this environment.These characteristics show a very high correlation to the primary dispersion haloes of shear zone gold deposits in the other part of the world. Based on these similarities of the behaviors, the other geochemical exploration patterns in the primary environments might be used for the Kurdistan mineralized areas to prioritize the anomalous area for follow up exploration.

Today, the use of Knelson centrifuge and Gemeni table in placer gold processing plants has replaced traditional gravity separator such as Gig, Spiral and Shaking tables. The 90 to 95 percent recovery rate in plants using these new technologies has led to the increasing use of these machines in placer gold processing plants. In this paper increasing of recovery of placer gold using Gemeni table and Knelson centrifuge has studied. The samples were taken from Damghan’s kohe zar mine. Grade of samples were 0.52 ppm. Studied effective parameters on operation of Knelson were: rate of dry feed (400-520 gr/min), speed of bowl (60-100% of total power) and pressure of water (1-3 psi). The tests designed according to Tagouchi tests plane. Finally at the optimum operational condition the obtained recovery and grade of concentrate were values 93.92% and 19.8 ppm, respectively. The notable point in this project is, we selected final concentrates of Kelson as feed of Gemeni table tests. Studied effective parameters on operation of Gemeni table were such as: Frequency of Gemeni table, flow rate of wash water and rate of feed. Recovery and grade values of concentrate obtained: 87.9% and 60 ppm, respectively.

Chain pillars are placed between two adjacent panels in mechanized longwall mining. These pillars have different load distribution comparing with the other kind of pillars in various mining methods. Estimation of load and its distribution on chain pillars are very important from designing point of view. Empirical and traditional methods have some limitations for load prediction and its distribution. So in this study by using of Mohr-Coulomb strain softening failure model of FLAC3D software, the load and its distribution on the chain pillars were estimated. As a result, based on Tabas coal mine conditions, it can be concluded that the maximum load distribution will happened at 4 to 5 meter distance from the first edge of pillar while the face is 20 meter after from there.

Shear wave velocity provides petroleum engineers with the valuable information to manage efficient processes in the development of hydrocarbon reservoirs. Shear wave velocity (Vs) plays a prominent role in characterizing some important reservoir properties such as lithology, pore fluid type, productive zone, etc. Since using well logging is too expensive, Vs is not available in all wells. In this case, a wide variety of empirical relationships have been published for different lithologies in which Castagna and Greenberg are of the first rank. Greenberg and Castagna (1993) have given empirical relationships in multiminerslic, brine-saturated rocks based on representative polynomial regression coefficients for pure lithologies represented by Castagna. In addition, Gassman relationships should be applied to fulfill assumption of brine saturation. The present study carried out in an Asmari reservoir of an oil field in Sothwest Iran which has a Vs log. In the present paper, firstly, Gassman relationships are applied to replace the common fluid. So compressional wave velocity (Vp) is calculated in the condition of brine saturation. Note that, Greenberg-Castagna relationships are empirical and should be modified for the studied reservoir. This modification done in two different phases due to lithology and water saturation. Finally, regression coefficients of Castagna used for prediction of Vs in limestone and shale. Also, regression coefficients of first and second modifications are respectively used for dolomite and sandstone to predict the Vs. According to results, correlation coefficients between real and predicted values are 0.84 and 0.94 respectively before and after modification, which prove the superiority of modified model of Greenberg-Castagna.

Heavy media cyclones have found a wide application in gravity separation of minerals. In this research, the initial separation of gangue minerals of the Lakan lead and zinc flotation feed was investigated. The results of float-sink experiments using 1-10 mm feed material, indicated that, the gravity separation is possible. Therefore a pilot-scale heavy media cyclone was designed and established. Optimization of this cyclone, using the design of experiments technique, was investigated. It was shown that at certain levels of effective parameters, including; inlet pressure of 3 psi, cyclone inclination of 10 degree, the ratio of media to feed of 2.8, the recovery of 83.9% and 88.4% for lead and zinc, respectively, was achieved. The assay of lead and zinc in the concentrate were 2.86% and 8.66%, respectively. As a result around 44% of the flotation feed, as low assay tailings, was removed. Therefore, by removing a part of siliceous gangue from the flotation feed, in this stage, the plant capacity could be increased twice as its present capacity.

Qomroud Tunnel with the length of 35.7 kilometers is one of the greatest national projects. EPB type tunneling machine has been selected for boring of lot 1 with the length of 11+311 kilometers. Prediction of utilization factor is very important for prediction of advance rate and afterward project complete time and costs. Utilization factor is defined as the machine boring time net divided by the available total time of each geology unit. This factor is depends on geology conditions, machine type, back up installations, project management and finally worker’s experience. The NTH and CSM methods are the most important methods that are used for prediction of utilization factor in countries. In this article a method which has the closer values to actual utilization factors has been presented for achievement to utilization factors. Then TBM utilization factor has been predicted for each tunnel path geology unit by three ways and has been compared with actual data for 4570 meter length which has been bored and then tunnel boring accomplishment time has been predicted. The goal of the article is representation of a model for so accurate estimation of utilization factors and finally correct decision of project scheduling and the income and cost prediction in TBM excavation projects.