Underground Infrastructure Project Descriptions

Colorado School of Mines

1: Evaluation of Mechanical Properties of Geopolymer Concrete

Project Number: 1

Faculty Mentors: Dr. Reza Hedayat

Mine tailings are left over materials from mining operation that, in addition to heavy metals and contaminants, can contain valuable components. Our current research has shown great promise in converting tailings into valuable cementitious materials through the Geopolymerization process. The geopolymerization involves alkali-activation of the existing aluminosilicates in tailings to produce high strength and durable concrete. The main goal of this REU research project is to evaluate the mechanical and durability characteristics of geopolymerized tailings for construction applications. The figure here shows the loading machine being used for testing a geopolymer specimen in flexture (bending).

The research activities for the REU student will be as follows: (a) review and finalize the specific research objectives in collaboration with the faculty mentor; (b) create geopolymerized concrete in the laboratory; (c) conduct uniaxial compression, flexure, and durability tests on the produced specimens; (d) evaluate the test results in collaboration with the faculty mentor; and (e) prepare research manuscript for dissemination of the research findings in a conference.

 

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2: Elucidating the process-structure-performance relationship of biochar for concrete

Project Number: 2

Faculty Mentors: Dr. Lori E. Tunstall

Our lab has demonstrated a nearly 40% increase in the compressive strength of cement mortars through replacement of 15% of the cement with wood biochar—a carbon rich, renewable additive made from pyrolysis of pine. We estimate that this innovation will offset the CO2 emissions associated with concrete by over 48%, when compared to traditional cementitious materials. However, more work is needed to improve our understanding of the process-structure-performance relationship fast pyrolysis biochars and their behavior in biochar mortars (Figure 1).

Biochar mortar

Figure 1: Biochar mortar

Preliminary results show deviation in the microstructural characteristics of two nominally identical chars and a corresponding change in the strength improvement properties of the mortars. The reason for this is not well understood; however, before this technology is viable, we need to ensure that we understand the process well enough to make predictable improvements to the concrete. Our data also indicate a decrease in the flexural strength of biochar mortars compared to a control, and an increase in carbonation in samples with biochar (in excess to any biochar decomposition), which increases with increasing biochar loading. Our hypothesis to explain these results is that the carbonic acid on the surface of the biochar reacts with the calcium hydroxide from the cement hydration reaction to produce calcium carbonate at the surface of the biochar, resulting in an expansive product that damages the biochar/cement interface. This effect would be particularly pronounced during flexural testing.

The objective of this REU project is twofold: 1) to improve our understanding of the effect of various biochar characteristics on mortar properties and 2) to explore solutions to the observed decrease in flexural strengths. The research activities for the REU student will include the following: (a) review and finalize the specific research objective in collaboration with faculty mentor; (b) make mortars with varying types and quantities of biochar; (c) test mortars for compressive and flexural strength; (d) measure the surface acidity of biochars before and after treatment, and quantify acid site concentration via titration methods; (d) conduct sensitivity analysis to determine critical biochar characteristics to control; (e) develop a hypothesis to explain results; and (f) discuss results and hypothesis with faculty mentor and develop a research plan for future work

 

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3: Modeling Flat Roofed Excavation Stability

Project Number: 3

Faculty Mentors: Dr. Gabe Walton

While many excavations are developed using a circular or arched geometry, tunnels and caverns in layered sedimentary rock are commonly developed with a flat-roof. This geometry, based on the rock’s anisotropic nature, allows beam-building principles to be applied when developing primary support designs. The Voussoir beam is a theoretical analog of a fractured beam that can be used to study the mechanics of this type of scenario. While several analytical solutions have been proposed that predict the deflection and failure of individual Voussoir beams, few studies have used this approach to consider the behavior of multi-layered beams tied together by rockbolts, which is the scenario relevant to excavation design.

Modeling Flat Roofed Excavation Stability

The research tasks for this project will be to (1) develop a plan for which Voussoir beam scenarios and parameters should be evaluated based on existing studies; (2) modify existing code to simulate the scenarios of interest using the discrete element method; (3) analyze model results to evaluate the potential for prediction of multi-layered supported beam behavior using modified Voussoir beam analytical solutions.​

 

 

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4: Investigating the possibilities for mixing of foam and Clay to get a consistent mix for testing of their flow properties

Project Number: 4

Faculty Mentors: Dr. Jamal Rostami

Earth Pressure Balanced (EPB) Tunnel Boring Machines are the most common tunneling machines in the world. In particular they are the best choice of machines in soft ground tunnels involving Clay formations. To improve the machine performance and reduce the wear and tear on the machine, often foam is injected at the face, to condition the soil.  The behavior of Soil-Foam mixture is not fully explored and in particular a proper mixing of clay and foam for evaluating the behavior of the mixture has been an obstacle. The proposed research is experimental work that involves looking at various ways that clay and foam can be mixed to develop a uniform material for testing. The work involves reading background information, conducting tests on various soil types to see the impact of soil conditioning on soil behavior and measurement of proper parameters on a recently developed soil rheology testing unit shown in the picture below. The student will receive proper introduction to the topi and will be trained on operating the testing unit.

 

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LEHIGH UNIVERSITY

5: Evaluation of Ultra High Performance Concrete (UHPC) for Underground Structures - Recruiting two students

Project Number: 5

Faculty Mentors: Dr. Spencer Quiel and Dr. Clay Naito

Figure 1: Tensile test setup for UHPC specimens

Figure 1: Tensile test setup for UHPC specimens

Ultra High Performance Concrete, also known as UHPC, has been gaining traction in the U.S. construction industry for use in bridges and buildings. These materials provide a minimum compressive strength of 17,000 psi (in comparison conventional structural concrete has a strength of 4000 psi). As such these materials can be used with limited or no steel reinforcement and instead rely on high strength steel fibers to provide tensile capacity. UHPC materials were traditionally available as proprietary mixes which were expensive to use, however, recent development of non-proprietary mixes has allowed for a wider adoption.

The research effort will examine different UHPC mixes and determine the mechanical and thermal properties. These results will be used to assess the performance of the material under both conventional loads and fire events in tunnel systems. The experimental program will consist of fabrication of UHPC mixes, tension and compression testing of materials, high temperature exposure of samples and determination of residual strengths.

Figure 2: Oven for high temperature exposure testing

Figure 2: Oven for high temperature exposure testing

The research activities for two REU students will include the following: (a) review and finalize the research objectives in collaboration with the faculty mentors; (b) collect information on conventional UHPC mix designs; (c) design lab tests to investigate the performance of UHPC during and after fire exposure; (d) define failure mechanism of UHPC exposed to heat; (e) utilize the experimental results to propose recommended designs for tunnel applications. One student will focus on thermal performance of UHPC over a range of temperature conditions, and the other will focus on thermo-mechanical response to applied loading and restraint of thermal expansion.

 

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6: Tunnel Liner Panel Joint Flexural Study

Project Number: 6

Faculty Mentors: Dr. Clay Naito and Dr. Spencer Quiel

Precast concrete segmental tunnel liners, installed via tunnel boring machines (TBMs), have become increasingly used in modern tunnel construction. The objectives for this REU research project are to characterize the moment-rotation response and failure modes of the radial joints between segments when subjected to a combination of out-of-plane loading and restraining arching action.  This work will establish mechanically fundamental understanding of the response of these joints, which will benefit the tunnel construction community in the design and implementation of these systems.

Figure 3: Schematic drawing of test configuration

Figure 3: Schematic drawing of test configuration

Six flexural joint tests will be conducted at Lehigh’s Fritz Laboratory to validate computational models and perform parametric studies of these joint characterizations at ambient conditions. Figure 3 shows the test configuration for flexural joint tests. Students will assist with testing and data acquisition under the supervision of mentors and laboratorial technicians. The goal of this training is to provide enough fundamental knowledge for the student to be involved in defining the project and take ownership of their research.

The research activities for the REU student will include the following: (a) review and finalize the specific research objectives in collaboration with the faculty mentors; (b) assist lab technicians with test setup as demonstrated in Figure 3; (c) predict the behavior and performance of tunnel liner segments when subjected to out-of-plane loading; (d) determine appropriate loading time-histories for vertical loads and horizontal loads during flexural joint tests; (e) test the concrete compressive strength and split tensile strength of the tunnel liner segments; and (f) collect the test results and integrate them into a report or a journal publication.

 

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7: Seismic Fragility of Tunnels and their Role in Transportation Network Resilience

Project Number: 7

Faculty Mentor: Dr. Paolo Bocchini

The disaster insurance sector plays two crucial roles to support our communities: (1) before disasters occur, it facilitates risk communication, providing immediate monetary value to retrofit and mitigation interventions, in the form of lower premiums or access to more policies; (2) after disasters, it is responsible for a growing share of the financial resources that fuel recovery. Traditional actuarial science calculates premiums and exposure based on a statistical analysis of historical claims. However, when dealing with rare events like earthquakes, past data is insufficient. Therefore, instead of using a purely data-driven approach, the science of Catastrophe Modeling combines the limited available data with engineering models, to calculate risk.

Figure 4: Bridges and tunnels in a transportation network

Figure 4: Bridges and tunnels in a transportation network

The results of a previous REU student confirmed that the damage on tunnels can have catastrophic effects on transportation networks and severely hinder the post-disaster recovery phase, with large losses. This project will build upon these preliminary results, to identify methods to compute the risk associated with tunnel failures due to various types of hazards. In particular, the research activities for the REU student will include the following: (a) review of the state-of-the-art and the state-of-practice on tunnel risk assessment under multiple hazards, to finalize the research objectives in collaboration with the faculty mentor; (b) perform a survey of the relevant structural fragility models for roadway tunnels, in the scientific literature and in software programs; (c) become familiar with the OASIS platform and its functions; (d) integrate in the platform selected sets of fragility curves for tunnels; (e) perform portfolio risk analysis for the tunnels of a selected region. Depending on the level of experience of the student, task (b) may or may not involve original analyses to compute novel sets of fragility curves. During this effort, the REU student will be supervised by the faculty advisor and mentored by graduate students and postdocs who worked extensively with all the necessary tools.

 

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California State University – Los Angeles

8: Sand Partial Drainage Testing under an Undrained Cyclic Simple Shear Setup - Recruiting two students

Project Number: 8

Faculty Mentors: Dr. Wing Shun (Welson) Kwan

Confined variable direction dynamic cyclic sheer apparatus (VDDCSS-CON)The research project’s objective is to generate Partial Drainage (PD) data from ‘undrained’ simple shear tests on clean sands. Previous geotechnical laboratory studies that have investigated PD conditions in soil were mostly performed with a triaxial setup; however, there are no documented studies using a simple shear setup. The simple shear device more accurately simulates the upward propagating seismic shear waves during an earthquake, so it is generally preferred in sand liquefaction engineering designs. Cal State LA recently acquired a Confined Variable Direction Dynamic Cyclic Simple Shear Apparatus (VDDCSS-CON) for soil properties characterization. Custom filtration devices will be integrated to further enhance the ability of the VDDCSS-CON to conduct simple shear tests under various degrees of partial drainage. This project will investigate the liquefaction capacity of Ottawa sand at various drainage conditions. The generate data that is virtually non-existent and will be useful for constitutive model calibrations.

The VDDCSS-CON is friendly to operate; hence it is ideal for training student researchers. The REU students will work on the following tasks: (1) Assist the PI to conduct undrained simple shear tests, (2) Interpret simple shear test results under various loading paths and drainage conditions, and (3) Evaluate the effects of partial drainage in sand liquefaction.

 

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9: Underground Infrastructure Assessment with SAR Sensors

Project Number: 9

Faculty Mentors: Dr. Jingjing Li

Remote sensing of infrastructures from satellites has proven its benefits for the detection and monitoring of facilities because of the large spatial coverage and cost-effectiveness of monitoring. Among the remote sensing systems, the Synthetic Aperture Radar (SAR) have been increasingly utilized by the scientific community to assess the performance of underground infrastructure in recent years. Such process involves SAR image acquisition and processing as well as the SAR integration with current databases. The main goal of this project is to understand the satellite remote sensing data applicable to evaluate the performance of underground infrastructure and perform the necessary data processing steps to detect the underground objects.

The REU students will work with the faculty mentors to learn the fundamentals of remote sensing systems, and more specifically SAR imagery, to perform image acquisitions and data processing of geo-referenced data, such as Geographic Information System (GIS) files, to integrate with current underground infrastructure databases. The students will be able to employ collected satellite information to perform various studies regarding the performance of the underground infrastructure such as the ground movements and surface deformation measurements.

 

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10: Infrastructure Defect Monitoring and Forecasting with Artificial Intelligence

Project Number: 10

Faculty Mentors: Dr. Mohammad Pourhomayoun

The integrity of materials in infrastructure is essential to ensure durability and safety. Concrete is a common construction material due to its performance, durability, and cost-effectiveness. Concrete structures are prone to develop surface cracking during their lifetime. Identifying and assessing these defects is important for decision-makers to take any necessary maintenance actions to prevent further deterioration and potential failure. Machine Learning is an effective tool that have been applied to this and many other fields to automatically obtain meaningful information instead of manually developing complicated analytical models.Infrastructure Defect Monitoring and Forecasting with Artificial Intelligence

This study proposes a machine learning method to predict the growth pattern of cracks on the concrete surface. The REU student will work with the faculty mentor to a) analyze the images for capturing the partial propagation of individual cracks with the aim of producing a series of frames that predict the continuation of the growth sequence over time, b) Employ various machine learning algorithms to achieve the best prediction performance, and c) Implement transfer learning and data augmentation to deal with a limited dataset.

 

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