An adaptive neuro fuzzy inference system to model the uniaxial compressive strength of cemented hydraulic backfill

Purpose. The purpose of this paper is to develop the models for predicting the uniaxial compressive strength (UCS) of cemented hydraulic backfill (CHB), a widely used technique for filling underground voids created by mining operations as it provides the high strength required for safe and economical working environment and allows the use of waste rock from mining operations as well as tailings from mineral processing plants as ingredients. Methods. In this study, different modelling techniques such as conventional linear, nonlinear multiple regression and one of the evolving soft computing methods, adaptive neuro fuzzy inference system (ANFIS), were used for the prediction of UCS, the main criterion used to design backfill recipe. Findings. Statistical performance indices used to evaluate the efficiency of the developed models indicated that the ANFIS model can effectively be implemented for designing CHB with desired UCS. As proved by the performance indicators ANFIS model gives more compatible results with the expert opinion and current literature than conventional modelling techniques. Originality. In order to construct the models a very large database, containing more than 1600 UCS test results, was used. In addition to widely used conventional regression based modelling techniques, one of the evolving soft computing methods, ANFIS was employed. Numerical examples showing the implementation of constructed models were provided. Practical implementation. As proved by the statistical performance indicators, the developed models can be used for a reliable prediction of the UCS of CHB. However, more accurate results can be achieved by expanding the database and by constructing improved models using the algorithm presented in this paper.Мета. Побудова моделей для прогнозування межі міцності при одноосьовому стисканні цементної гідравлічної закладки для заповнення вироблених просторів шахт. Методика. Для досягнення поставленої мети були використані різні методи моделювання: лінійна та нелінійна множинна регресія, а також порівняно недавно став популярним метод програмування – адаптивне нейронечітке логічне виведення (ANFIS). За їх допомогою було спрогнозовано зміну міцності на одноосьове стискання, що є ключовим показником для визначення складу закладної суміші. Для побудови моделей використана значна база даних, яка включає результати більш ніж 1600 випробувань на одноосьове стискання. Лабораторними дослідженнями також визначалися властивості закладних матеріалів і суміші. Результати. Модель ANFIS дала найкращу продуктивність з урахуванням статистичних показників ефективності, таких як середня абсолютна процентна похибка і змінний обліковий запис. Статистичні показники продуктивності, які використовуються для оцінки ефективності розроблених моделей, свідчать, що моделювання за допомогою ANFIS дозволяє отримати результати, які більше відповідають експертній оцінці та даним з сучасної літератури, ніж інформація, отримана за допомогою традиційного моделювання. Встановлено, що на відміну від регресивного моделювання, ANFIS не вимагає заздалегідь визначених математичних рівнянь для взаємозв’язку між вхідними та вихідними змінними і використовує наданий набір даних для ефективного визначення структури моделі. Наукова новизна. Вперше для прогнозування міцності при одноосьовому стисканні були використані не лише традиційні способи моделювання, засновані на регресії, а й інноваційний метод програмування – адаптивне нейронечітке логічне виведення ANFIS. У статті наведені чисельні приклади впровадження нових побудованих моделей. Практична значимість. Статистичні індикатори продуктивності показали, що розроблені моделі можуть бути використані для надійного прогнозування міцності при одноосьовому стисканні й оптимальної рецептури закладної суміші. Однак, щоб отримати більш точні результати, необхідно мати більш широку базу даних і створити більш досконалі моделі на основі алгоритму, запропонованому в даній статті.Цель. Построение моделей для прогнозирования предела прочности при одноосном сжатии цементной гидравлической закладки для заполнения выработанных пространств шахт. Методика. Для достижения поставленной цели были использованы различные методы моделирования: линейная и нелинейная множественная регрессия, а также сравнительно недавно ставший популярным метод программирования – адаптивный нейронечеткий логический вывод (ANFIS). С их помощью было спрогнозировано изменение прочности на одноосное сжатие, что является ключевым показателем для определения состава закладочной смеси. Для построения моделей использована обширная база данных, которая включает результаты более чем 1600 испытаний на одноосное сжатие. Лабораторными исследованиями также определялись свойства закладочных материалов и смеси. Результаты. Модель ANFIS дала наилучшую производительность с учетом статистических показателей эффективности, таких как средняя абсолютная процентная погрешность и переменная учетная запись. Статистические показатели производительности, используемые для оценки эффективности разработанных моделей, свидетельствуют, что моделирование с помощью ANFIS позволяет получить результаты, которые более соответствуют экспертной оценке и данным из современной литературы, чем информация, полученная при помощи традиционного моделирования. Установлено, что в отличие от регрессионного моделирования, ANFIS не требует заранее определенных математических уравнений для взаимосвязи между входными и выходными переменными и использует предоставленный набор данных для эффективного определения структуры модели. Научная новизна. Впервые для прогнозирования прочности при одноосном сжатии были использованы не только традиционные способы моделирования, основанные на регрессии, но и инновационный метод программирования – адаптивный нейронечеткий логический вывод ANFIS. В статье приведены численные примеры внедрения новых построенных моделей. Практическая значимость. Статистические индикаторы производительности показали, что разработанные модели могут быть использованы для надежного прогнозирования прочности при одноосном сжатии и оптимальной рецептуры закладочной смеси. Однако, чтобы получить более точные результаты, необходимо иметь более широкую базу данных и создать более совершенные модели на основе алгоритма, предложенного в данной статье.The authors thank the staff and the managers of Jinfeng underground gold mine for their helps and cooperation during field and laboratory studies. The company is also acknowledged for the permission to use and publish the data

Creep Fractures in the Mantle and their role for Deep Fluid Transfer

When hot and ductile rocks fail they do so with an astonishing variety. Observations from crustal deformation show that when the fluid content is low (less than a few per cent) they form the cores of anastomosing mylonitic shear zones, which feature strong gradients in grain size towards their metamorphic fluid rich centre (Fusseis et al., 2009). In circumstances where the fluid/melt content is high they form macroscopically visible ductile fractures (Weinberg and Regenauer-Lieb, 2010) which allow melt transfer into the shallower crust forming the feeder zone of granites. We show here that all of the above phenomena are new types of instabilities well known from high temperature deformation of ceramics, i.e. materials that otherwise show brittle cleavage at cold laboratory conditions. The new failure modes boil down to a series of microscopic processes, where upon increasing temperature and decreasing applied stress failure modes transition from brittle cleavage to transgranular and intergranular “creep fractures”, summarized by Ashby’s classical deformation mechanism maps (Ghandi and Ashby, 1979). Although Material Scientists are well aware of these creep enhanced fracture modes we have been lacking concise evidence in the laboratory and field proving the existence of these failure transitions. As creep fracture processes are happening on relatively slow geodynamic time scales they have been argued to provide the critical mechanism linking plate tectonic processes and deep fluid transfer processes (Regenauer-Lieb, 1999). In these considerations fluids are viewed as creating their own pathways through facilitating shear localization by creep fractures, rather than being a passive constituent simply following brittle fractures that are generated inside a shear zone caused by other localization mechanisms. Recently, the missing laboratory (Rybacki et al., 2008) and field evidence for creep fractures have been found (Fusseis et al., 2009). Ghost images of both creep fractures and brittle fractures can also be seen in OH diffusion profiles on grain boundaries (Sommer et al., 2008) and fully embedded intragranular cracks in mantle xenoliths (Sommer et al., 2012). In order to illustrate the fundamental implications for deep fluid transfer we extend classical solutions of material sciences to geodynamic conditions and incorporate melting reactions into the numerical formulation. We will show the implications to a number of applied field studies

Thermal-elastic stresses and the criticality of the continental crust

Heating or cooling can lead to high stresses in rocks due to the different thermal-elastic properties of minerals. In the upper 4 km of the crust, such internal stresses might cause fracturing. Yet it is unclear if thermal elasticity contributes significantly to critical stresses and failure deeper in Earth's continental crust, where ductile creep causes stress relaxation. We combined a heating experiment conducted in a Synchrotron microtomograph (Advanced Photon Source, USA) with numerical simulations to calculate the grain-scale stress field in granite generated by slow burial. We find that deviatoric stresses >100 MPa can be stored during burial, with relaxation times from 100's to 1000's ka, even in the ductile crust. Hence, grain-scale thermal-elastic stresses may serve as nuclei for instabilities, thus rendering the continental crust close to criticality

Coupling and Damping Effects on the Dynamics of Submerged Expanded Tubes in Borehole Wells

Hydraulic expansion of submerged tubes is accomplished by propelling a mandrel through it using differential pressure. This process deforms the tube beyond its elastic limit. Toward the end of the expansion process, the mandrel pops out of the tube resulting in displacement, stress, and pressure waves propagating through the system. A mathematical model has been developed to describe the dynamics of the tube-fluid system due to the pop-out phenomenon. The model takes into consideration the coupling effect between fluids and the structure, as well as the inherent system damping of its response. An analytical solution describing the wave propagation in the tube-fluid system was obtained. The model identified the potential failure locations and showed that the inherent system damping reduced the chances of failure but could not eliminate it completely. In addition, it showed that the coupling effect was more prominent in the tube as compared to the outer and inner fluids. Furthermore, a sensitivity analysis was conducted in order to investigate the effect of the geometrical and material properties on the response. The sensitivity analysis showed that the coupling effect vanished with the increase in tube stiffness and reached an asymptotic value with an increase in formation stiffness

Evaluating force distributions within virtual uncemented mine backfill using discrete element method

International audienc

Axial impact behavior and energy absorption of rubberized concrete with/without fiber-reinforced polymer confinement

This study investigates the axial impact resistance and energy absorption of rubberized concrete with/without fiber-reinforced polymer confinement. The impact tests were carried out using an instrumented drop-weight testing apparatus. The experimental results have shown that rubberized concrete significantly reduced the maximum impact force of up to 50% and extended the impact duration. These characteristics make rubberized concrete a promising material for protective structures and particularly for future sustainable construction of rigid roadside barriers. Glass fiber–reinforced polymer confinement is a very effective method to improve the impact resistance for both conventional concrete and particularly for rubberized concrete. It was found that the rubberized concrete reduced the maximum impact force so that it transferred a lower force to a protected structure as well as a lower rebound force, which is desirable for protection of passengers in an incident of vehicle collision. Interestingly, the rubberized concrete showed a lower energy absorption capacity as compared to conventional concrete, where the exact reason for this is unknown to the authors. Therefore, further research is sought to provide more understanding of the response of rubberized concrete under impact and improve its energy absorption. This study explored experimentally the use of rubberized concrete as a promising sustainable construction material for applications to construction of columns in buildings located in seismic active zones or subjected to terrorist attack, security bollards and rigid road side barriers

From transient to steady state deformation and grain size: A thermodynamic approach using elasto-visco-plastic numerical modeling

Numerical simulation experiments give insight into the evolving energy partitioning during high-strain torsion experiments of calcite. Our numerical experiments are designed to derive a generic macroscopic grain size sensitive flow law capable of describing the full evolution from the transient regime to steady state. The transient regime is crucial for understanding the importance of micro structural processes that may lead to strain localization phenomena in deforming materials. This is particularly important in geological and geodynamic applications where the phenomenon of strain localization happens outside the time frame that can be observed under controlled laboratory conditions. Ourmethod is based on an extension of the paleowattmeter approach to the transient regime. We add an empirical hardening law using the Ramberg-Osgood approximation and assess the experiments by an evolution test function of stored over dissipated energy (lambda factor). Parameter studies of, strain hardening, dislocation creep parameter, strain rates, temperature, and lambda factor as well asmesh sensitivity are presented to explore the sensitivity of the newly derived transient/steady state flow law. Our analysis can be seen as one of the first steps in a hybrid computational-laboratory-field modeling workflow. The analysis could be improved through independent verifications by thermographic analysis in physical laboratory experiments to independently assess lambda factor evolution under laboratory conditions