Journal of Engineering Geology

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One of the tests that is used for the characterization of soil abrasivity, is LCPC test. LCPC test device is designed for measuring the wear particles as small as pebbles (4-6.3 mm). In this study, some of the most important abrasive minerals were collected from different parts of Iran for analyzing the effect of the geological parameters on the ability of abrasive minerals. Firstly, amount of index minerals abrasivity is measured according to three standards of AFNOR P18-553, AFNOR P18-579 and AFNOR P18-560 that are the preparation of samples for testing, procedure of laboratory tests and analysis of grain size with laboratory sieves. The effect of geological parameters affecting the wear rate of the sample, including five parameters of shape, size, angularity and saturation rate of the environment, has been studied. The effectiveness of these parameters on the abrasivity of samples are studied according to NF ISO 5725 relating to usage of statistics, the accuracy of test method, the repeatability and the ability to reproduce a standard way of testing within laboratory (based on classification index X 06-041). Finally, after ensuring significant effect of these parameters on the abrasivity of minerals by help of SPSS, abrasivity rates for types of minerals that have the hardness below 7 in the Mohs hardness scale, have been predicted.

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Unpredicted and excessive tool wear is a major challenge in some tunnel projects. Due to more need for maintenance, abrasivity problems increese time and cost of excavation activity. A new laboratory test machine has been built in Engineering Geological Laboratory of Ferdowsi University of Mashhad, to obtain a proper view about relation between performance parameters of a TBM and the soil abrasion. In this paper the results of abrasion tests carried out on silica samples, as an abundant hard mineral, by the machin, are presented. Hence 36 tests have been performed on coarse silica sand samples, with various amount of deadweight and rotation speed at different times. The results prove direct relation between time, surcharge and rotation speed versus tool wear. For example a linear relation between tool wear and surcharge or rotation speed was observed. Besides a logarithmic relation was achieved for time effect

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Aggregates are one of the high demand building materials in construction of structures and their characteristics have important effects on durability and permanence of projects. Abrasion resistance is one of the important features of aggregates that their utilization in concrete and asphalt are affected by texture and lithology of them. As rock consisted of harder minerals have higher abrasion resistance like igneous rocks, due to more siliceous minerals. More varieties in mineralogy compound usually lead to increase in aggregate abrasion. Aggregates that are contained of different minerals usually have less abrasion resistance. Porosity usually decreases the resistance abrasion. In addition to lithological properties, the environment where aggregates are deposited is important in determining resistance-related parameters of aggregates.
Rivers, alluvial fans, and taluses are the main environments where aggregates are deposited. Geological processes, such as weathering and particle movement may cause changes in natural aggregates, hence affecting their abrasion and impact resistance. Rock weathering can results in increasing porosity, producing minerals that are weaker in comparison to their original rock.
In the process of particles transport by stream water, weak parts of aggregates will be omitted. The present study is focused on the relationship between geology medium and the weight loss of aggregate in Los Angeles test. 
Methodology
Considering that lithology features in aggregates resistance against abrasion have an important role, in order to examine the effect of various geology environments in abrasion resistance of aggregates, the medium should be chosen having similar lithology. Therefore, the north of Damavand and the south of Daneh Khoshk anticline (north of Dire plain) were firstly chosen by using geology map, satellites images and field study. Damavand zone consists of trachyte and trachy-andesite volcanic rocks. These rocks cover the whole area around the Damavand peak. Also, Daneh Khoshk anticline is covered by thick Asmari formation. The selected environment are in the length of each other. Such that taluses feed alluvial fan and alluvial fans feed rivers. Samples were collected from different area of southern part of anticline. 10 river area, 12 alluvial fan and 6 taluses in the south-west area of Daneh Khoshk anticline (north of Dire plain) were chosen. Los Angeles test has been done according to standard A method ASTM D2216-10, 1990 on samples and the results were analyzed by analogous analyzer.
Results and discussion
Results show that porosity and micro-crack percentage increase, respectively in accumulated aggregate in river, alluvial fans and taluses areas. Also, porosity and micro-crack in various alluvial fans is different and is influenced by the area and length of main channel of alluvial fans’ catchment. The porosity decreases by the increase in the length of channel and area of alluvial fans’ catchment.
The percentages of aggregate weight loss in talus, alluvial fan and river areas decreases, respectively. Based on the obtained results, the lowest rates of weight loss belong to river environments (23.7 % in Daneh Khoshk and 42% in Damavand) whereas the highest rates of weight loss belong to taluses (49.3% in Daneh Khoshk and 48% in Damavand). The alluvial fans have an average state. Another noticeable point is the high weight loss in Los Angeles test in Damavand aggregate. Due to having harder mineral, igneous aggregate have more abrasion resistance, but this research illustrates that the weight loss resulting from Los Angeles test in these aggregates is high. This is because of virtues texture that weakness against the impact as well as their high porosity.
Conclusion
The result of this research indicates that the volume of aggregate weight loss in Los Angeles test is related to aggregate accumulation environment. The extent of aggregate abrasion resistance is lowest in talus medium and increases in alluvial fan and river environment, respectively. The difference in aggregate abrasion resistance in various areas result from geology process differences that applies to aggregates in various environment. The extent of caring particles in talus environment is very low and the type of movement is mass or sliding type in these media, micro-crack and weak parts remains within aggregates. The surface of micro crack is weak such that breaks easily in Los Angeles test due to the pressure results from the impact of aggregate, as well as the impact of steel ball on aggregate leading to aggregate breakages. Aggregates move more distances in alluvial fan and river. Aggregate strike together in riverbed and alluvial fan yielding to aggregates breakages from micro-cracks. As the movement distance increases, aggregates approach more to intact rock. During the particles move, the weathered and weak parts are damaged by aggregate abrasion to riverbeds and alluvial fan, and more resistant and harder aggregates remain. As the water current increases, the aggregates impact each other harder, more resistant micro-crack breakages and this change leads to decrease the weight loss in Los Angeles test.
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Introduction
Urban development and rapid extension of cities have been accompanied by a considerable growth in mechanized tunneling. The abrasivity of rock and even soil is a factor with considerable influence on the wear of tools. Soil abrasion and the resulting tool wear has a major impact on machine operation, utilization, and tunneling costs and time. One of the problematic aspects of working in abrasive grounds is the frequent need for the replacement of cutting tools, especially in pressurized face tunnel boring machines (TBMs). The effect of worn and damaged TBM cutter heads has been documented for numerous tunnel projects around the world. However, the lack of a standard or universally accepted test for soil abrasivity in geotechnical investigations has made the prediction of tool wear a difficult task.
Material and methods
A reliable prognosis of the abrasiveness of soils on a project would be of great benefit for designers, clients, and contractors. Many abrasion tests exist for rocks, and some have been proposed for soils; however, there is no universally accepted or international standard test for soil abrasivity testing. One of the most important and available tests in this field is LCPC abrasivity test which was developed by the Laboratoire Central des Ponts et Chaussées in the 1980’s. The LCPC Abrasivity Coefficient (ABR or LAC) can be used as a measure for both the abrasivity of the soil material and the influence of the grain size. The  abrasivity  testing  of  rock  is  controlled  by well-known parameters, whereas in soils many factors are influencing the abrasivity such as in-situ soil conditions, sedimentary petrology and technical   properties.
Tabriz metro line 2 Project about 22 km in length that will connect eastern part of the Tabriz city to its western part, considered as a case study. The project comprises a single tunnel which has been constructed using two earth pressure balance EPB-TBM with a cutting-wheel diameter of 9.49 m. In this study, based on geological and geotechnical properties, the tunnel route was divided into four parts and the abrasion and brittleness coefficients of alluviums determined by LCPC test. Besides that, the influences of some factors such as moisture content, mineralogy, grain size and shape, type and amount of foam have been studied.
Results and discussion
Based on more than 130 LCPC test results, in general, the Tabriz Metro’s line-2 route alluviums have the abrasion in the range of low to very high and the brittleness in the range of high to very high. In order to measure the effect of moisture content on abrasion and brittleness coefficient, the LCPC test was done on some samples related to the tunnel route in dried and moistened modes (5%, 0%, 15%, 20%, 25%, and 30%). Three types of sandstone, andesite, and conglomerate of the route were used to test the effect of moisture and petrology on abrasion. In a moisture range of 0 to 5%, in all types of materials, abrasion was increased. In a moisture range of 5 to 10%, abrasion was decreased in all three types, and this shows that a moisture level of 10% is a normal moisture content to create minimum abrasion. The behavior of sandstone and conglomerate is similar at higher moisture contents, and an increase in moisture content to 30% can increase abrasion of materials in both types. In conglomerate, abrasion at higher moisture levels is significantly more than in other modes. In andesite, an increase in moisture content to 20% can increase abrasion, although the abrasion is decreased with a moisture content of over 20%. In most samples, increase in moisture content led to decrease in brittleness of materials. In general, the highest abrasion level was related to conglomerate and the lowest level was related to sandstone. Moreover, andesite was at a lower level than conglomerate and a higher level than sandstone in terms of abrasion. Also, the results show that increased grain size led to increased abrasion, and the changes in andesite were greater than in sandstone.
In order to test the effectiveness of foam on abrasion, the foam used in workshops (A 168) made by Komeil Company Kashan was used for four types of petrography: conglomerate, andesite, sandstone, and silica. This test was conducted in the range of dried to 100 ml foam. In all types, decreased abrasion is observed from 0 to 20 ml and increased abrasion is observed from 20 to 100 ml.
Conclusion
The following conclusions are drawn from this research.
- With regard to the effect of grain size, increased size of grains could lead to more abrasion and less brittleness
- In terms of the effect of mineralogy, the conglomerate had the most effect on abrasion. In terms of brittleness, andesite was the most brittle.
- When the foam is moisturized in the sample, minimum abrasion is observed and above this level, the abrasion is increased.
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