Soil Abrasion Research Articles

Investigations on Geotechnical Aspects for TBM Specification on the Tabriz Metro Line 3, Iran

In order to perform a successful mechanized tunnelling, detailed surface and subsurface investigations on ground are key factors for proper TBM selection and design of machine technical specification. Adverse geological conditions encountered by boring machine during tunnelling, provides a great challenges and may trigger serious hazards especially in urban areas. This paper focused on investigation of geotechnical properties and relevant issues for mechanized tunnelling in the Tabriz metro line 3. Geological units of the tunnel alignment consist of alluvium deposits (fine to coarse grained with some cobble and boulder) in south and north parts and alternation of layers of soft rocks (marlstone, sandstone and mudstone) in the middle portion. Principal objects including detailed assessment of physical and mechanical parameters, soil grain size distribution, percentage of fine-grain content, equivalent quartz content, permeability and consistency have been investigated. Main geotechnical problems are occurrence of oversized rock particles, mixed face condition, soil abrasivity and clogging in the tunnel alignment and basically clear subsurface geological models to study these problems are constructed. Finally based on obtained data the proper TBM type and additional conditioning material for each section of the tunnel are suggested. In order to perform a successful mechanized tunneling, detailed surface and subsurface investigations on ground are key factors for proper TBM selection and design of machine technical specification. Adverse geological conditions encountered by boring machine during tunneling, provides a great challenges and may trigger serious hazards especially in urban areas. This paper focused on investigation of geotechnical properties and relevant issues for mechanized tunneling in the Tabriz metro line 3. Geological units of the tunnel alignment consist of alluvium deposits (fine to coarse grained with some cobble and boulder) in south and north parts and alternation of layers of soft rocks (marlstone, sandstone and mudstone) in the middle portion. Principal objects including detailed assessment of physical and mechanical parameters, soil grain size distribution, percentage of fine-grain content, equivalent quartz content, permeability and consistency have been investigated. Main geotechnical problems are occurrence of oversized rock particles, mixed face condition, soil abrasivity and clogging in the tunnel alignment and basically clear subsurface geological models to study these problems are constructed. Finally based on obtained data the proper TBM type and additional conditioning material for each section of the tunnel are suggested.

Tool wear analysis of pressurized face TBM drives in the glacial geology of the Pacific Northwest

AbstractFor underground construction projects in the United States and Canada it is standard procedure to use a Geotechnical Baseline Report (GBR) to contractually define subsoil conditions. The GBR sets baselines based on which tunneling contractors develop bids and plan the works. Baseline values for soil abrasiveness are a focus especially where drives with pressurized‐face Tunnel Boring Machines (TBM) beneath the groundwater table and in unstable face conditions require changing the cutterhead tools under hyperbaric conditions or in pre‐constructed safe havens. Several laboratory procedures exist that can be used for providing soil abrasiveness baselines in the context of the GBR. However, none of them cover all the soil characteristics that are relevant in causing tool wear. Also, other factors need to be considered for wear rate prediction. Analyzing the performance of previous TBM drives is a proven way to gain insight into the wear system behavior. This paper presents correlation analyses of geotechnical conditions, TBM operational data, and tool wear measurements from several TBM drives in the metropolitan areas of Seattle and Vancouver, B.C. These drives with earth pressure balance and slurry TBMs include various tool types and were conducted in glacial and interglacial deposits that are considered highly abrasive.

Application of an interval wear analysis method to cutting tools used in tunneling shields in soft ground

The replacement of cutting tools is important when shield tunneling in abrasive soils. The task is performed based on an assessment of the degree of cutting tool wear. The wear of cutting tools is influenced by many factors, such as the soil abrasiveness, shield machine operational parameters, and tool sliding distance. The representation of the uncertainty in these factors is the primary problem in the evaluation of tool wear. Instead of real variables, interval variables are employed to represent the uncertainty in the influencing factors, and the interval of the tool wear amount is attained based on interval arithmetic operations. With the calculated interval for the amount of tool wear and the dimensionless indices η and ξ, the feasibility of completing shield tunnel construction with tool wear within a predefined tolerance is quantitatively evaluated. Measures and countermeasures can be implemented based on the results of the evaluation. A five-step process for conducting an evaluation is described and explained using an example application. The suggested methodology can help realize active tool replacement and obtain cost-effective and less-disruptive solutions for shield cutting tool wear in tunnel construction.

The RUB Tunneling Device – A newly developed test method to analyze and determine the wear of excavation tools in soils

The efficiency of a tunneling project is mainly associated with the abrasivity of the acting soil and the wear resistance of the cutting tools. Heavy wear can dull the cutting tool, which negatively affects the penetration rate and therefore the efficiency of a tunneling process. Completely worn tools with a short service life have to be replaced by newer ones. This circumstance results in unplanned machine shutdowns and higher maintenance costs. It is thus of high economic as well as technical interest to obtain a deeper understanding of soil/cutting tool interactions during tunneling. To meet this challenge, a large number of different testing devices to estimate the abrasivity of soils have been developed within the last two decades. An innovative and promising experimental setup is presented in this work. A horizontal implementation offers the possibility of simulating a tunneling process as well as the tribological system of a TBM tool. The interactions between all system components can be mapped and analyzed in detail. This method offers a unique setup, which allows wear prediction of TBM tools in a homogeneous soil with project-specific parameters (soil composition/condition, soil mechanics, tool material and machine/tunneling data).

Proposed soil classification based on the experiences of soft-ground tunneling in Iran

An essential step in successful mechanized and conventional tunneling operations is a thorough characterization of ground conditions and identification of geological and geotechnical risks. In bored tunneling, this and other information is needed in order to select the appropriate tunnel boring machine (TBM) and to determine its technical specifications for proper soil conditioning and optimal TBM performance. In conventional tunneling, this information is also important for ensuring the correct choice of drilling method and minimizing drilling risk. The major geological risks in tunneling (New Austrian Tunneling Method [NATM] or mechanized) are stickiness and clogging of soils, soil abrasi veness, soils with low fine content or oversized grains, tunnel collapse and instability, groundwater fluctuation, mixed-face conditions, liquefaction, and soil movement. Experiences from both conventional and mechanized tunneling in Iran show that the potential for each geological hazard is higher in certain types of soils. As such, knowledge of the various soil types is important for predicting soil behavior and possible geological hazards. In this study, we present a simple and practical classification of soil types for the prediction of soil behavior and geological hazards in both conventional and mechanized tunneling. With this method, soils are classified based on two parameters. The first is soil grain distribution. For this purpose, tests were conducted on soil samples from the test pit and geotechnical boreholes, and the percentage of particles remaining above a no. 4 sieve and those passing through a no. 200 sieve were calculated for each sample. The second parameter is the consistency index, which is estimated from the Atterberg limits. The soils were classified into ten groups based on these two parameters, and soil behavior and geological hazards for each class were then predicted based on Iranian tunneling experiences. Finally, the real soil behavior and geological hazards in the Qom tunnel were analyzed to determine the accuracy of the predictions. The results showed that the predictions were largely comparable to actual conditions. These results were then directly used for preliminary and permanent lining design and recommendations for soil conditioning, as well as for structural design of the different stations.

Experimental Study of Coarse Soil Properties Influencing Soil Abrasivity

The paper reports selected results of a study on tool wear for mechanized tunnelling in coarse soil. Several laboratory soil abrasion tests were performed and the results correlated with mineralogical composition, shape and surface roughness of the grains and the grain size curve of the soils. The analysis of the results clearly confirms the well-known correlation between soil abrasivity and quartz content and, for the soils tested, can quantify the relevant influence of grain size and grain roughness. We also report and discuss results useful for quantifying the positive effect of the addition of different chemical agents, injected as foams in a process known as soil conditioning, commonly performed in mechanized tunnel excavation using tunnel boring machines whit earth pressure technology to minimise tool consumption.

Impact of some geological parameters on soil abrasiveness

A systematic estimation of the amount of tool wear is nearly impossible because there is no universally accepted test for determining soil abrasiveness. Laboratory devices that have been developed in recent years have fewer limitations than older methods, but they are unique and are under development. A new device has been developed and used at the Ferdowsi University of Mashhad, Iran, to evaluate how geological factors affect soil abrasion behavior. Samples with known geological characteristics including hardness (mineralogy), grain size, and grain roundness were prepared and tested using the new abrasion test unit. The results indicate a direct linear relationship between the relative mineral hardness (Mohs scale) and abrasion. Moreover, the results of the abrasion testing showed increasing abrasion with grain size and angularity. Furthermore, the impact of moisture content was also examined, and the amount of measured wear followed an approximately bell shaped curve relative to the water content, as has been reported in similar studies by other research groups. Additional testing of the samples for shear strength showed a good correlation between the shear strengths of the specimens and the abrasivity.

Geological–geotechnical risk in the use of EPB-TBM, case study: Tabriz Metro, Iran

The essential requirements of a successful tunnel boring machine (TBM) tunnelling operation are complete characterization of the ground and thorough identification of geological and geotechnical risks. This paper predicts the geological and geotechnical risks of Tabriz Urban Railway Line 2 (TURL2) in Iran. The railway consists of a 9.5-m-diameter, 22-km-long tunnel and 20 stations. The tunnel passes through a soft alluvial sedimentary combination of clay (CL), silt (ML), sand (SM, SP) and gravel (GP). The tunnel alignment has been divided into three parts subject to the geological and geotechnical conditions that might be encountered during construction. The investigated geological–geotechnical risks of the soft ground along the TURL2 are oversize grains, soil abrasiveness, liquefaction potential, differential permeability and clogging. The results show that all of the investigated geological–geotechnical risks are present in the TURL2 route and that improvement of the tunnel route soils is essential. For example, to reduce the liquefaction potential, it is necessary to decrease the water table level or else improve the soft soils by injecting cement grout. In addition, in order to reduce clogging of the tunnel route soils, the use of foam as a soil conditioner is appropriate.

Identification and evaluation of post-depositional mechanical traces on quartz assemblages: An experimental investigation

The evaluation of the state of preservation of archaeological lithic artefacts is the first step before starting a functional analysis. If lithic artefacts show a variety of damage from many contact materials, they are also subject to modifications from “natural” causes, such as water transport, soil abrasion, trampling etc. Studying alteration features gives us information to reconstruct the life story of lithic tools after their abandonment and helps us to better understand formation processes of archaeological sites.Prolonged movements under soil could be responsible for post depositional surface modifications that sometimes look like wear traces due to use. These alterations could have chemical and/or mechanical origin. Recognizing them is of paramount importance especially on quartz assemblages where usewear analysis requires a long and complex methodology that differs to a certain extent from the protocol applied to other artefacts produced with different raw materials such as flint, obsidian etc … For this reason, the use wear and post-depositional surface modification analysis on quartz and quartzite tools have been undertaken by very few researchers until now. The aim of this paper is to increase the experimental quartz field through the attempt to recreate mechanical contact between quartz flakes and sediments such as in archaeological contexts.Through the use of a Polishing Machine MECAPOL P320 equipped with two counter-rotating platens, it was possible to wear out two experimental flakes in a sandy quartzite sediment coming from Sai Island (Sudan) for 240 h.After the experimentation, the two flakes showed no edge damage or other visible modifications, but some micro traces on the crystal surface were present. Although long and demanding, this step sharply reduces possible errors in the recognition of use-wear during the experimental stage. The micro traces definable as abrasions on some parts of the crystal surface, have been analysed by a metallographic microscope and compared with the same crystal portion taken before the experiment. Even if it is difficult to reconstruct post depositional processes in a laboratory, this attempt shows that the contact between sediment and stone tools in a continuous movement can randomly abrade the crystal surface.

Suggestion of an empirical prognosis model for cutting tool wear of Hydroshield TBM

The wear of cutting tools is a major issue in tunneling with Hydroshield TBM in soils, because it is a common reason for downtime. The replacement of cutting tools requires access to the excavation chamber, which is only possible with hyperbaric works or at fixed positions with prearranged grout blocks. In order to improve predictability of the maintenance stops, an empirical prognosis model for the wear of the cutting tools was developed. Based on the new Soil Abrasivity Index (SAI), the model helps to estimate distances between maintenance stops and the required amount of cutting tools to be changed. The authors validated the prognosis model based on the original reference projects. The validation leads to an adaption of the prognosis process and individual correction factors in the model itself. The article describes the updated prognosis model and validation results.

Parametric study of soil abrasivity for predicting wear issue in TBM tunneling projects

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.

The effects of soils and soil stay on the egg morphology of Neotropical Eulimnadia (Branchiopoda: Limnadiidae)

Studying the species distribution of Limnadiidae, a family of crustaceans, in environments favourable to their growth and reproduction is made difficult by their extremely short life cycle and the transient existence of adult forms. However, the eggs of these branchiopods are highly resistant to environmental extremes and persist in the soil of humidified and dried pools. We therefore studied the capacity to detect populations of Limnadiidae and identify them at the species level using egg morphology. We investigated influences of pool sediments on Eulimnadia (clam shrimp) egg morphology and asked whether we could rely on this morphology after various lengths of time in the soil to recognise species. We studied sediment collected from temporary pools in four Neotropical areas: Minas Gerais and Bahia (Brazil), French Guiana, and Martinique. These samples represented diverse geographical regions and climates and allowed us to study the four most widely distributed Eulimnadia species in the Neotropics: E. colombiensis, E. cylindrova, E. geayi, and E. magdalensis. Our results indicated that soil abrasion is superficial and does not affect the general shape of the eggs (cylindrical or spherical). However, details of egg ornamentation can be severely affected by the combined effects of erosion and filling with sediments, which can lead to difficulties in species identification. In the particular case of the spherical eggs of E. magdalensis, this species cannot be unequivocally identified without clean eggs collected from adults after breeding or from eggs recently deposited in the field. This work and the investigative methods described herein should facilitate identification of Eulimnadia species and promote further study of Limnadiidae crustaceans in the field.

Experimental study of the effect of conditioning on abrasive wear and torque requirement of full face tunneling machines

One of the main operational parameters in pressurized full face soft ground tunneling with machines such as earth pressure balance (EPB) TBMs is soil conditioning. Soil conditioners which are proper foam or conditioning agents, are often injected through the cutterhead or into the cutting chamber to make the muck flowable, lower inner friction between the soil particles, control soil stickiness, prepare the excavated soil to be compressible during the tunneling operation, control the water inflow, reduce the torque on the cutterhead, and lower power and torque of the screw conveyor. Foams can also be used in hard rock tunneling to reduce the wear and torque to replace conventional dust suppression by water sprays. This paper reviews the common practice in soil conditioning and focuses on assessing the influence of the conditioning on tool wear and torque requirement of the machines. Tests performed on many standard type soils and few samples from soft ground tunneling projects around the US on Penn State Soil Abrasion testing device. The results of tests performed in dry, moist and conditioned soil will be discussed and compared in this paper. The preliminary results show that the use of proper soil conditioning can reduce the wear of cutters and machine components by orders of magnitude while it can reduce the torque by over 50%.

Development of the Soft Ground Abrasion Tester (SGAT) to predict TBM tool wear, torque and thrust

The Norwegian University of Science and Technology (NTNU), SINTEF Rock Engineering and BASF Construction Chemicals have jointly developed a new test device called the Soft Ground Abrasion Tester (SGAT). The ambition and purpose of the design of the test and the applied test procedure is to replicate an in situ soil – TBM excavation tool contact, in a small and simplified scale. The current development is attempting to bridge a gap when it comes to estimating soft ground and soil abrasivity, as earlier research on e.g. the NTNU/SINTEF Soil Abrasion Test™ (SAT) shows that it does not catch up all driving factors for soft ground and soil abrasivity directly. The paper summarizes the development of the SGAT apparatus, and shows its capabilities to evaluate, quantify and compare how the soil mineralogy, water content, pressure, compaction, and the use of soil conditioning additives influences the wear rate on the SGAT excavation tool. During testing the required torque and thrust are monitored and logged, making it possible to measure various soil–soil conditioning matrixes requirement for operational parameters.

Engineering geological investigations of mechanized tunneling in soft ground: A case study, East–West lot of line 7, Tehran Metro, Iran

The essential requirements of a successful TBM tunneling operation are the complete characterization of the ground and the thorough identification of geological and geotechnical risks. These besides other information are needed for selecting the right TBM and determining its technical specifications for proper soil conditioning and for achieving the optimum TBM performance. This paper concentrates on a methodology for engineering geological investigations and geotechnical ground characterization, which is important for successful application of mechanized tunneling methods in soft alluvial sediments along the East–West section of line 7 of the Tehran Metro. Geotechnical considerations related to tunneling with a soft ground TBM are described in detail, including the site investigation program, project-specific soil grouping system, distribution of soil types, geological–geotechnical risks (oversize grains, clogging, soil abrasiveness, fine grain content, permeability and groundwater fluctuation) and the engineering geological subsurface model. The encountered soil materials have been divided into four categories according to physical characteristics and engineering properties. In this study, the characteristics of the ground and the hydrogeological regime indicate that an EPB-TBM is rather a slurry-TBM. Although the engineering geological conditions of the ground along the tunnel are favorable for EPB-TBM, stickiness of fine-grained soils, abrasiveness of soils, existence of coarse-grained soils with low fine content and groundwater fluctuations are the most important risks for applying mechanized tunneling method in this specific project.

Challenges of methods and approaches for estimating soil abrasivity in soft ground TBM tunnelling

The increase of urbanization constantly demands more infrastructure, which often requires to utilize the underground. The complex functioning of Tunnel Boring Machines (TBM) and the complexity of their working environment make arriving at wear predictability a challenging affair. The economic consequence of tool wear is, on the other hand, significant. There are several methods and approaches to estimate geo-material's abrasion properties in tunnelling with TBMs. The methods are mainly based on using empirical observations and experiences from completed tunnelling projects correlated with simplified laboratory test results. The simplified laboratory tests means that the soil's in-situ properties such as the cohesion, density, adhesion, water content and original grain size distribution are lacking or is disturbed. The intention of this research paper is to give a brief overview the respective test procedures of the different approaches and their pros and cons. In light of these, we assess a new methodological approach and examine the extent to which it is capable of advancing the understanding of predicting wear on TBMs with respect to general tribological experiences such as the influence of hard minerals or particles, grain shape and grain size. The applicability of the laboratory experiments from a practitioner's point of view is equally briefly discussed.

Review and assessment of the NTNU/SINTEF Soil Abrasion Test (SAT™) for determination of abrasiveness of soil and soft ground

Measuring soil abrasivity for excavation tool life estimation, is becoming more necessary as tunnels are longer and with limited access to execute interventions and tool changes from shafts. The tool life is a major contributor to the tunnel excavation costs and tunnelling progress. The aim of this paper is to explain the consequences of tunnelling in abrasive soil and soft ground conditions, and explain the NTNU/SINTEF Soil Abrasion Test™ (SAT) which is one approach to measure soil abrasivity. In this paper a total of 254 different soil samples (clay, silt, sand and gravel are represented) originating from 8 different countries have been tested and included in the discussion of the SAT™ procedure’s applicability. Further, the paper relates the SAT™ test values to commonly known tribological theories regarding abrasion as well as presenting trends and correlations between the measured SAT™ value and measured scraper, ripper and disc cutter life from a total of nine completed TBM/pipe jacking projects, excavated with slurry shield face support.

A newly developed soil abrasion testing method for tunnelling using shield machines

The importance of the effect of ground abrasivity on the performance of a tunnel boring machine (TBM) is important for many tunnelling projects. In recent years, many abrasivity devices have been developed to measure soil abrasivity for specific conditions. In this paper a new device is developed to estimate the abrasivity of the soil for a wide range of site conditions. The device is designed on the basis of simulating the site conditions regarding the ground water, ground stresses and confining pressure of the TBM chamber, and the performance of the rotating cutter-head and pressurized shield tunnelling during its operation. A number of abrasivity tests were carried out on 12 types of crushed rock samples including six sedimentary rocks and six crystalline igneous and metamorphic rocks. The results showed that the abrasivity of the samples increased as equivalent quartz percentages of the sample increased. It was also found that the texture of the samples has a great influence on their abrasivity. To evaluate the performance of the newly developed device, the same samples were tested by other current abrasivity methods including the Cerchar test, Laboratoire Central des Ponts et Chaussées (LCPC) test and soil abrasion test (SAT). Comparisons of the results indicated close correlations, especially with the results for the Cerchar and LCPC devices.

Evaluation of Granular Soil Abrasivity for Wear on Cutting Tools in Excavation and Tunneling Equipment

AbstractThis paper presents an experimental study of tool wear and abrasivity of granular soils using a testing system specifically designed for the evaluation of wear on earth-moving machines, especially soft ground tunneling applications where the impact of soil abrasion on the operation is significant. In the testing system, a propeller fitted with steel covers of different hardnesses is rotated at 60 rpm in granular soil samples in a chamber under ambient pressures of up to 10 bar. The developed system can quantitatively assess the abrasive characteristics of soils through the measurement of weight loss on the special covers of the propeller, accounting for soil gradation, mineral composition, sphericity and roundness, water content, and tool hardness. Preliminary test results indicate that water content, particle angularity, and relative hardness between the tool and soil have significant impact on tool wear and soil abrasion. For the tests conducted, it is observed that angular sands produce signifi...

Abrasividad y su influencia en el rendimiento de una excavación mecanizada

Palabras clave: desgaste de herramientas de corte, abrasividad, rendimiento de tuneladorasThe use of Tunnel Boring Machines TBM is becoming more and more frequent although its optimization requires the accurate evaluation of various geotechnical risks, among them, the effect of soil abrasiveness in the cost and