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This paper presents an experimental study of tool wear and abrasivity of granular soils using a testing system specifically designed for the evaluation of wear in soft ground tunneling applications. In the testing system, a propeller that is fitted with steel covers with different hardness is rotated at 60 rpm in granular soil samples in a chamber...
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... labor-intensive tunneling methods, they are mainly bored by using tunnel boring machines (TBM). These machines are used for excavation of long tunnels in a variety of geological conditions. The total number of TBMs that were utilized for soft ground tunneling between 2005 and 2010 is approximately 350 units worldwide as reported by Home (2010). Fig. 1 presents an illustration of cutterhead wear in a TBM. Although there are some cases of tunnels being above groundwater table, in most cases the tunnel alignment is below groundwater table or below river beds. Therefore, as a result of water and earth pressure, cutterhead inspection and maintenance is required to be performed in extreme ...
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... investigate the effect of water content on the relationship of weight loss versus hardness ratio, sand mixtures at w 5 15% and w 5 22:5% were tested using the covers with 51 HRC. Fig. 10 compares the results of these tests with those performed in dry condition as shown in Fig. 9. Fig. 10 demonstrates that the effect of water content on the relationship of weight loss versus hardness ratio is complex. At the water contents of w 5 0% (i.e., dry condition) and w 5 15%, an increase in water content may increase or decrease ...
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... investigate the effect of water content on the relationship of weight loss versus hardness ratio, sand mixtures at w 5 15% and w 5 22:5% were tested using the covers with 51 HRC. Fig. 10 compares the results of these tests with those performed in dry condition as shown in Fig. 9. Fig. 10 demonstrates that the effect of water content on the relationship of weight loss versus hardness ratio is complex. At the water contents of w 5 0% (i.e., dry condition) and w 5 15%, an increase in water content may increase or decrease weight loss depending on the hardness ratio. At these two water contents, weight loss decreases as ...
Citations
... Due to the demand in long-distance and large-diameter tunnel construction in abrasive ground, there are studies beginning to evaluate the wear failure of irregular cutting tools. For example, Alavi Gharahbagh et al. [19,20,[68][69], Rostami et al. [11], Jakobsen et al. [30], Küpferle et al. [15,70] and Wei et al. [71][72] considered the weight (or volume) loss as an valuable parameter to estimate the wear failure of simplified cutting tools. Bosio et al. [73] and Salazar et al. [54] proposed a feasible procedure combining profilometer and microscope to obtain shape parameters (such as curvature radius, area loss and volume loss) to quantify the wear failure of special cutting tools. ...
... Parametric studies on soil abrasivity for predicting tool wear failure of shield TBMs have been carried out in recent years. Rule of thumb between the simplified cutter mass (or volume) loss, soil parameters, cutter properties and soil additives has been explored by soil abrasion tests (such as NTNU, LCPC, PSAI, SGAT, SATC, RUB, WHU-SAT etc.) [11,15,19,20,30,[37][38]54,[68][69][70][71][72][73]. With the development of the irregular cutting tool evaluation method, quantitative relationship between the mass (or volume) loss of simplified cutting tool and the CVWR and CHWR of actual cutting tool are required to be established. ...
... A preliminary literature survey indicates that soil abrasion testers have been developed to study the influence of soil parameters on cutting tool wear (Plinninger and Restner, 2008;Peila et al., 2012;Rostami et al., 2012;Jakobsen et al., 2013a;Düllmann et al., 2014;Barzegari et al., 2015;Mirmehrabi et al., 2016;Küpferle et al., 2016;Salazar et al., 2018;Wei et al., 2018;Hamzaban et al., 2020). For instance, Alavi Gharahbagh et al. (2011Gharahbagh et al. ( , 2014, Rostami et al. (2012) and Mosleh et al. (2013) developed the PSAI soil abrasion tester and studied the influence of equivalent quartz content and water content on soil abrasivity. Jakobsen and Lohne (2013) and proposed the SGAT soil abrasion tester to evaluate the effect of water content and soil density on cutting tool wear. ...
... TSAT (Vinai et al., 2008;Peila et al., 2012;Salazar et al., 2016Salazar et al., , 2018Bosio et al., 2018) ≤40 Gharahbagh et al., 2011Gharahbagh et al., , 2014Rostami et al., 2012;Mosleh et al., 2019) D 50 = 7 HRC = 17-60 ...
... It is related to the physical and mechanical parameters of sand samples. According to Alavi Gharahbagh et al. ( , 2014 and Hamzaban et al. (2019), cutting tool wear is positively correlated with sand compacted density. When the compacted density is around the maximum dry density, cutting tool wear reaches the maximum value. ...
When shield TBM tunneling in abrasive sandy ground, scrapers are loaded with heavy forces resulting from the extrusion and friction processes of sand particles. Scraper wear reflected as displacement or desquamation is related to soil parameters. Due to the lack of reliable test methods, experimental studies on the influence of soil parameters on scraper wear are limited. In the present study, existing soil abrasion testers have been reviewed to discuss the advantages and deficiencies. An improved WHU-SAT soil abrasion tester has been developed to study the influence mechanism of soil parameters on scraper wear. Experimental studies have been conducted to evaluate the variation of scraper wear with quartz content, particle size, particle shape and water content. Two soil abrasion tests have been performed for each case. Scraper wear has been considered to be the average value. The results indicate that scraper wear increases with the increase of quartz content and the growth rate increases. It is related to the particle crushing and adhesion effect of limestone sand. As the average particle size increases, the extrusion and friction between the modeled scraper and the sand particles increases first and then decreases. Thus, scraper wear increases first and then decreases with the increase of average particle size. The trend is generally comparable to the corresponding changes in scraper wear with water content. As quartz balls collide with sand particles and destroy the microscopic friction system composed of scrapers and asperities, scraper wear decreases as the increase of roundness and the falling rate decreases. Optimized solutions such as soil abrasivity evaluation, tunnel alignment optimization and soil discharge improvement have been proposed to alleviate the influence of soil parameters on scraper wear. The present study promotes the rational estimation of sand abrasivity and scraper consumption during the feasibility study of abrasive sandy gournd tunneling using shield TBM.
... Due to the importance of the issue, various testing devices and procedures have been developed in the recent decade to assess the abrasive properties of soil and rock materials. In the soil abrasivity sector, the most noteworthy methods are LCPC abrasion test [3], soil abrasion test (SAT) [4,5], soft ground abrasion test (SGAT) [6], Penn State abrasion index (PSAI) [2,[7][8][9][10], soil abrasion testing chamber (SATC) [11,12], and RUB tunneling device [13,14]. The results from different testing methods have revealed that there is a direct correlation between the average diameter of soil grains and the measured wear amount at the end of the test [3,10,13,[15][16][17][18][19]. ...
ncreasing demand for the application of mechanical excavation techniques in various civil and mining projects has increased the importance of ground abrasive properties and its mechanized excavatability. The accurate prognosis of cutting tools lifetime has crucial importance in the planning of mechanized tunneling projects. Moreover, the precise estimation of the required cutter number for excavating the determined length of a given section in a specific geotechnical condition is one of the main tasks of the project consultants. The main objective of these estimations is to assess the needed time and cost of cutter replacements in the phase of feasibility studies and to plan a proper maintenance schedule. The LCPC testing procedure is one of the simplest and most common soil abrasivity assessment methods. The purpose of the presented study is to investigate the steel – soil interaction during the LCPC abrasion test. The consumed energy of LCPC tests on different abrasive samples was measured. Based on the recorded energy values, a new parameter of wear specific energy of the LCPC test (WSEL) was introduced. The obtained WSEL values showed meaningful correlations with the sample grains size and the sample average hardness. Moreover, the results revealed that the high LCPC abrasion coefficient (LAC) values are relevant to the high consumed energy levels recorded during the tests.
... It was found that working in abrasive materials can reduce steel undercarriage life from 14,000 hours to 3,000 and the abrasiveness impacts not only tracks but other areas of the machine (Elverman, 2004). Adding moisture to the abrasive sand types has a "significant impact" to the abrasivity impacting the wear components (Gharahbagh et al., 2014). Other input factors could include topography, machine operator techniques and the type of work being performed. ...
... This supports the studies done by lee, Kim and Youn which found wear rates are directly related to the abrasivity of the soil (Lee et al., 2014). This also supports the study done by Gharahbagh, Qiu and Rostami that adding moisture has significant impact to machine component wear rates (Gharahbagh et al., 2014). Further research could be initiated to further substantiate the cause and effect of these input factors and to further understand why there are differences in median undercarriage wear rates between territory store location and geological region. ...
The estimation of soil abrasivity and cutting tool wear during soft ground tunneling is complicated and arduous work due to the lack of a generally accepted testing system. To date, geotechnical baseline reports (GBRs) and geotechnical data reports (GDRs) still cannot provide reliable soil abrasion indices for tool life prediction. This is considered a deficiency in the geotechnical investigation of shield-driven tunnel projects. In this study, the Multifunctional Shield Test System (MSTS) developed by the Key Laboratory of Safety for Geotechnical and Structural Engineering of Hubei Province at Wuhan University is presented. The MSTS was motivated by the need for a test platform with the ability to simulate undisturbed soil conditions and actual tool working environments to explore the mechanism of cutting tool wear, bentonite slurry penetration, and filter cake formation in various geomaterials with grain sizes including clay, silt, sand, and gravel (< 15 mm). Experimental studies on the effect of alloy hardness on cutting tool wear are conducted. The soil samples used in the tests are dense fine silty sand from the Sutong GIL Yangtze River Crossing Cable Tunnel. When the wear extent is plotted against the alloy hardness, an inverted S-shaped band bounded by the highest and lowest alloy hardnesses is formed. The sensitive hardness interval is HRC = [47, 52]. If the alloy hardness is higher than 52 HRC, the wear extent is relatively small. Since alloy hardness is negatively correlated with bending strength, using a cutting tool material with a hardness slightly higher than the upper limit of the sensitive hardness interval is optimal. Thus, an alloy with a hardness interval of HRC = [52, 63] is recommended for the dense fine silty sand ground at the Sutong GIL Yangtze River Crossing Cable Tunnel.
In mechanized excavation projects, the major part of feasibility studies includes predicting the lifetime of cutting tools. Estimating the required numbers of tools for excavating a certain length of a section, under defined geologic conditions, and assessing the cost and downtimes needed for tools replacement are the other important issues in the preliminary studies of these projects. Presently, there are several experimental models used to study the abrasive capacity of soil materials in mechanized tunneling applications. In this paper, the effect of plastic behavior of clay particles on the abrasivity of soil materials was studied using the results of LCPC abrasivity tests. The results showed that the rheological behavior of abrasive samples changes considerably with the change of the clay particles mineralogy and the dominant water content. These changes have a significant effect on recorded wear amounts. Based on the obtained results, the plastic limit and the liquid limit of the clay part can be used to predict the appeared abrasive trends in LCPC tests. Moreover, during performing the LCPC tests, the consumed power of the electromotor of the testing device was recorded. The obtained power graphs confirmed the effect of the mineralogy and the water content of the clay part on the rheological and abrasive behavior of the testing samples.
The development of mechanized tunneling technology and the extent of its application in the soft grounds have revealed the importance of soil abrasivity studies more. As one of the first methods of soil abrasivity assessment, LCPC test is widely used in predicting the wear of cutting tools in soft grounds. In this study, the effect of water content, rotation speed, and applied stress on the abrasivity of crushed silica particles are investigated with the LCPC tests. The results showed that water content has a considerable effect on the abrasive behavior of silica particles. The occurrence of drainage during the tests considerably changed the dominant conditions of moisture and affected the observed wear rates. The obtained correlation between the effective stress levels and recorded
wears showed that the theory of granular soils compaction can be used to describe the variations of soil abrasivity with water content changes. Moreover, the results showed a direct linear correlation between the rotation speed of steel propellers and measured wears. The same correlation was also found between effective stress levels and wear amounts. However, in the samples with higher water content than 10 percent, the effect of stress on the wear rates increases with the increase of propeller rotation speed.
The lack of reliable methods for evaluation of soil abrasivity and revealing the effects of different parameters on wear rate are nowadays considered as a deficiency in geotechnical investigation during feasibility study, design and construction phases of tunneling projects with the use of tunneling boring machine (TBM). The subject is recently attracts a broad international attention and focus.
The background of existing standard test methods are reviewed and wear types occurrences in TBM tunneling are discussed in this paper. A new soil abrasion testing system is developed which is called Soil Abrasion Testing Chamber (SATC) and the results of soil abrasion tests are compared with results of the commonly used tests such as: Cerchar, LCPC and SAT tests. Some of the most influencing factors including presence of water, bentonite slurry, soil particle size, quartz content, water pressure and confining chamber pressure are considered for the use of the new devise. The test results indicate that the soil abrasivity tends to increase with the increasing of soil particle size, bentonite slurry, soil pressure and quartz content. The effect of water on abrasivity varies for different types of soil. The soil abrasivity decreases with the increase of water pressure. The internal friction does not seem to have any influence on the wear rates measured with the new proposed apparatus.
