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School of Civil and Environmental Engineering

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Start date: 2020 × End date: 2024 × Author: Patino-Ramirez, Fernando ×

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Now showing 1 - 4 of 4
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    Deformation and failure mechanisms of granular soil around pressurised shallow cavities
    ( 2021) Patino-Ramirez, Fernando ; Ando, Edward ; Viggiani, Gioacchino ; Caicedo, Bernardo ; Arson, Chloé
    The deformation patterns and failure mechanisms of pressurised cavities at shallow depth are of relevance to many geotechnical applications, including tunneling and horizontal directional drilling. In this paper, we present an experimental study of a reduced-scale pressurised cavity under geostatic stress, in order to measure the effect of cavity length, vertical stress and soil density on soil deformation and failure. x-ray computed tomography is used to acquire images of the system at key stages of the cavity inflation process. A closed shaped failure region developed around the cavities, beyond which, shear planes of elliptic paraboloid shape formed, extending from the bottom of the cavities all the way to the free surface. The plane strain assumption did not hold beyond the central portion of the longest cavity tested (L = 6D). The volumetric strain and porosity changes inside the shear bands showed significant dilation in dense specimens, but contraction in loose specimens. The average orientation and the thickness of the shear bands were in agreement with those found in the literature for passive arching mechanisms (anchoring). The orientation of the principal strains around the cavity follows catenary shapes, similar to those displayed in active trapdoor mechanisms.
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    Transportation networks inspired by leaf venation algorithms
    ( 2020) Patino-Ramirez, Fernando ; Arson, Chloé
    Biological systems have adapted to environmental constraints and limited resource availability. In the present study, we evaluate the algorithm underlying leaf venation (LV) deployment using graph theory. We compare the traffic balance, travel and cost efficiency of simply-connected LV networks to those of the fan tree and of the spanning tree. We use a Pareto front to show that the total length of leaf venations is close to optimal. Then we apply the LV algorithm to design transportation networks in the city of Atlanta. Results show that leaf-inspired models can perform similarly or better than computer-intensive optimization algorithms in terms of network cost and service performance, which could facilitate the design of engineering transportation networks.
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    Horizontal directional drilling (HDD) alignment optimization using ant colony optimization
    ( 2020) Patino-Ramirez, Fernando ; Layhee, Carrie ; Arson, Chloé
    Horizontal Directional Drilling (HDD) is a trenchless method that consists in drilling an inclined and curved bore from an entry point to an exit point. In practice, HDD is designed iteratively by trial and error, to minimize the cost under geometric and mechanical constraints. In this paper, we optimize the drill path with continuous implementations of an Ant Colony Optimization (ACO) algorithm that sets the depth 15 of the alignment and its entry and exit angles as the design parameters to optimize, to ensure minimal drill path length (cost), avoid collapse or instability (mechanical constraints) and remain in the construction domain (geometric constraint). We compare the ACO results to the drill paths designed in practice in two different scenarios: one in which the entry and exit points are fixed, and one in which the geometry of the central 20 segment is constrained. Results show that ACO can be used to automate the otherwise time-consuming design process while minimizing the drill path length and the costs associated to it.
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    Modeling root system growth around obstacles
    (Georgia Institute of Technology, 2020) Jin, Wencheng ; Aufrecht, Jayde ; Patino-Ramirez, Fernando ; Cabral, Heidy ; Arson, Chloé ; Retterer, Scott
    State-of-the-Art models of Root System Architecture (RSA) do not allow simulating root growth around rigid obstacles. Yet, the presence of obstacles can be highly disruptive to the root system. We grew wheat seedlings in sealed petri dishes without obstacle and in custom 3D-printed rhizoboxes containing obstacles. Time-lapse photography was used to reconstruct the wheat root morphology network. We used the reconstructed wheat root network without obstacle to calibrate an RSA model implemented in the R-SWMS software. The root network with obstacle allowed calibrating the parameters of a new function that models the influence of rigid obstacles on wheat root growth. Experimental results show that the presence of a rigid obstacle does not affect the growth rate of the wheat root axes, but that it does influence the root trajectory after the main axis has passed the obstacle. The growth recovery time, i.e. the time for the main root axis to recover its geotropism-driven growth, is proportional to the time during which the main axis grows along the obstacle. Qualitative and quantitative comparisons between experimental and numerical results show that the proposed model successfully simulates wheat RSA growth around obstacles. Our results suggest that wheat roots follow patterns that could inspire the design of adaptive engineering flow networks.