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The process of creating a slope in a rock mass using the excavation and blasting methods consistently leads to stress release in the rock mass, resulting in a certain level of fracture and disturbance. Blast-induced vibrations can also influence the quality of the rock mass remaining after the blasting, as well as the stability and bench damage monitoring (BDM) of mines. A damage factor (D) is included in the Hoek–Brown failure criterion to compute the disturbance of a rock mass in creating a slope. Choosing the value and thickness of the blast zone for the Hoek–Brown criterion is crucial in the safety analysis and BDM of mines. However, the selection is still a crucial technical challenge in this criterion. Employing nonlinear layering, the present study divides the rock mass behind a blast hole into several layers with decreasing D values applied to each layer. The numerical simulation was conducted using the FLAC finite difference software for bench vibration assessment and damage monitoring by checking the peak particle velocity (PPV) in the bench face with different geometries. Behind the blast hole, five different layers of D were considered through which the Hoek–Brown properties of the rock mass declined nonlinearly during the execution of the model. Since the disturbance threshold of PPV was assumed to be 120 mm/s, the toe and middle parts of the small benches were in the disturbance threshold, while for the medium and high benches, only the bench toe was within the disturbance threshold., Proces stvaranja kosina u stijenskoj masi metodama iskopa i miniranja dovodi do oslobađanja naprezanja u stijenskoj masi, što rezultira određenom razinom loma i oštećenja. Vibracije izazvane miniranjem također mogu utjecati na kvalitetu minirane stijenske mase, kao i na stabilnost i praćenje oštećenja etaža (BDM) površinskoga kopa. Koeficijent poremećenosti stijenske mase (D) uključen je u Hoek-Brownov kriterij sloma za izračunavanje oštećenja stijenske mase pri izradi kosine. Odabir vrijednosti i širine zone miniranja prema Hoek-Brownovu kriteriju ključan je u analizi sigurnosti i BDM-a kopova. Međutim, odabir još uvijek predstavlja ključni tehnički izazov. Koristeći se nelinearnom slojevitošću, ova analiza dijeli stijensku masu iza minske bušotine u nekoliko slojeva sa smanjivanim vrijednostima D za pojedini sloj. Numerička simulacija provedena je korištenjem softvera FLAC za procjenu vibracija na etažama i praćenje oštećenja provjerom vršne brzine čestica (PPV) na etaži s različitim geometrijama. Iza minske bušotine razmatrano je pet različitih nizova D kroz koje su Hoek-Brownova svojstva stijenske mase nelinearno mijenjana tijekom analize modela. Budući da je granična vrijednost PPV-a pretpostavljena na 120 mm/s, vrh i središnji dijelovi malih etaža bili su na graničnoj vrijednosti oštećenja, dok je za srednje i visoke etaže samo vrh etaže bio unutar granične vrijednosti oštećenja.

When TBMs are applied for tunnel excavation in very strong and massive rocks, the cutting mechanism happening under the disc cutters is converted from chipping to grinding. On the other hand, the m...

Use of vital geomechanical parameters for determination of safe mud pressure window is generally associated with high level of uncertainty primarily because of absence of sufficient calibration data including laboratory and field test information. The traditional deterministic wellbore stability analysis methodologies usually overlooked the uncertainty of these key parameters. This paper exhibits implementing a quantitative risk assessment technique on the basis of Monte-Carlo modeling to consider uncertainty from input data so as to make it possible to survey not just the likelihood of accomplishing a desired level of wellbore stability at a particular mud weight, but also the impacts of the uncertainty in each single parameter on the wellbore stability. This methodology was implemented to a case study. The most important parameters have been recognized using a sensitivity analysis approach in which the outcome of this QRA procedure suggests the mud weight window with likelihood of well drilling success which can elude the wellbore collapse and lost circulation events. This sort of stochastic approach to deal with anticipated safe mud weight window can guarantee stable wellbore with considerable cost viability associated with drilling success. The technique built up in this paper can give the scientific foundation for assessment of wellbore stability under complicated geological circumstances. It was likewise noted that based on sensitivity analysis, uniaxial compressive strength and maximum horizontal stress are the most effective parameter in estimation of mud weight window. This accentuates the significance of trustworthy determinations of these two parameters for safe drilling of the future wells in the field.

Determination of in-situ stress serves as an important step in the design and construction of civil and mining projects, among others. Conventional methods of the in-situ stress measurement are time- and cost-intensive. Therefore, the application of low-cost yet rapid methodologies for in-situ stress evaluation has been increasingly regarded by researchers. The Kaiser effect-based acoustic emission method is one of such novel approaches to the in-situ stress evaluation. Not only the point at which the Kaiser effect occurs, but also the mechanism of the Kaiser effect is of paramount importance. In this research, acoustic emission tests were conducted on phyllite rock samples under Brazilian tensile loading to collect a variety of acoustic data, including the amplitude, rise time, count, duration, and energy. Then, the Kaiser effect point was determined using the collected data on acoustic parameters, with its occurrence mechanism investigated. In addition, mathematical transformations were adopted to transform the acoustic signal from the time domain to the frequency domain, where the peak frequency was analyzed. The results of the RA/AF ratio analysis showed that the acoustic emission was sourced from tensile micro-cracks. Moreover, the high level of energy indicated a high intensity of crack formation at the Kaiser effect point. The large number of received hits showed that the count of generated cracks increases abruptly within the range of the Kaiser effect. In addition, the obtained high value of the peak frequency implied that the crack growth rate is high at the Kaiser effect point., In situ određivanje naprezanja, među ostalim, služi kao važan korak u projektiranju i izradi građevinskih i rudarskih projekata. Konvencionalne in situ metode mjerenja naprezanja vremenski su i troškovno zahtjevne. Stoga istraživači sve više razmatraju primjenu jeftinih, ali brzih metodologija za procjenu in situ naprezanja. Metoda akustične emisije koja se temelji na Kaiserovu efektu jedan je od takvih novih pristupa u procjeni in situ naprezanja. Ne samo točka u kojoj se Kaiserov efekt javlja, nego i mehanizam Kaiserova efekta od iznimne je važnosti. U ovome su istraživanju provedena ispitivanja akustičke emisije na uzorcima filitnih stijena pri ispitivanju vlačne čvrstoće stijena uporabom brazilskoga testa kako bi se prikupili različiti akustički podatci uključujući amplitudu, vrijeme porasta, broj, trajanje i energiju. Potom je na temelju prikupljenih podataka o akustičkim parametrima određena točka Kaiserova efekta te je ispitan mehanizam njezina nastanka. Osim toga, usvojene su matematičke transformacije za transformaciju akustičkoga signala iz vremenske domene u frekvencijsko područje, gdje je analizirana vršna frekvencija. Rezultati analize omjera RA/AF pokazali su da je akustička emisija nastala iz vlačnih mikropukotina. Štoviše, visoka razina energije upućuje na visok intenzitet stvaranja pukotina u točki Kaiserova efekta. Velik broj primljenih impulsa pokazao je da se broj novonastalih pukotina naglo povećava unutar raspona Kaiserova efekta. Osim toga, dobivena visoka vrijednost vršne frekvencije implicira da je brzina širenja pukotine visoka u točki Kaiserova efekta.

Blast-induced disturbance is one of the major risks in rock engineering. Hoek et al. considered the disturbance factor (D) in the Hoek–Brown failure criterion. The lack of a detailed guide has led to technical challenges so that Hoek proposed numerical modeling to solve this problem. In this study, numerical modeling of a simple slope through 3D Distinct Element Code (3DEC) was carried out considering two modes of discontinuities to update and quantify the simple descriptive guide. Each of these modes was divided to 5 models based on rock mass properties, and then, the relevant borehole pressure was applied. Blast-induced dynamic changes were qualitatively analyzed using the failure zone capabilities in 3DEC analysis. The results were then quantitatively analyzed with the assist of Fish programming language using the recorded peak particle velocities values. The impact of an increase in burden and spacing on dynamic changes was investigated. According to qualitative analysis, discontinuities reduce the dynamic pressure; geological strength index (GSI) is related to the expansion of damage; and direction of discontinuities is effective in transferring the dynamic pressure. A coefficient of determination of 0.922 was obtained in quantitative analysis. Furthermore, the distance from the blasting site, dip of the discontinuities, GSI and the factor D had the highest impact on the rock mass damage, respectively. Based on the effect of the direction of discontinuities, type of rock mass, burden and spacing on the factor D, the previous estimation guide was updated.

Instrumentation and monitoring are common methods to control the stability of large underground spaces. During monitoring underground excavations, it is usually impossible for the instrument to fully record the displacements taking place ahead of the tunnel. This occurs due to the fact that there is always a distance between the instrument and the excavation face, so some displacement are lost before the installation of the instruments. In this research, efforts have been made to estimate the loss displacement of the Azad Pumped Storage Powerhouse cavern in Iran, using combination of numerical method and instrumentation results. For this purpose, according to the excavated sequence (pilot tunnel, downstream slashing, and upstream slashing) the roof of the powerhouse cavern was modeled, using two-dimensional finite element software, verified by the results obtained from extensometer installed in the cavern's roof. The comparison of modeling and monitoring results indicates that the displacement occurrence recorded via the instrument is less than the modeling values. The most obvious reason is the displacement loss and impossibility in recording all displacements via the instrumentation. Then, employing the results of the adjacent instruments and displacements recorded by the cavern roof's instrument and utilizing a combination of modeling results, the amount of loss displacements in the cavern's roof was evaluated to be 40% of the total displacements. Afterward, employing analytical methods and fitting the curve on instrument's results, the outcomes indicate that the longitudinal deformation profiles obtained by Hoek equation has the best fit, confirming the 40% of the displacements that occurred before the installation of the instrument.

This study mainly approaches evaluating the effect of air deck length (ADL) and its different positions (ADP) on blast-induced ground vibration and development of damage zone. The peak particle velocity (PPV) was used as a tool to achieve this goal. Three different positions (at top, middle, and bottom of the blast hole) in a rock slope under the blast load were simulated using 3D discrete element numerical code. The modeling was conducted in two modes: (1) columnar charge of blast hole and (2) considering an air gap in the explosive column with lengths of 1.5, 2, and 3 m. The PPV values at the ground surface were estimated continuously along a line from the blast hole collar to the end of the model. Finally, the results obtained from numerical simulations indicated that the use of air deck technique could reduce the costs of consumed explosive by 30 to 45%. It was also found that top column air deck increased the surface vibrations of the ground up to 36%. However, the middle and bottom column air decks have no significant effect on the reduction of blast-induced ground vibrations.

Ground settlement due to excavation of shallow tunnels is a common phenomenon. To control the settlement, one should be able to predict it, and based on it he may consider required preventions and protections. There are different methods for predicting settlement, each having some strengths and weaknesses. The main weakness of these methods is that they do not consider enough effective parameters on the settlement. The numerical methods, contrary to the empirical and analytical methods, take into account the effects of a larger number of parameters. However, ideal selection of many parameters is associated with ambiguity and difficulty and is time-consuming. To overcome these issues, the intelligent methods are incorporated which are appropriate tools. The aim of this paper is to present a numerical-intelligent model for prediction of maximum surface settlement (Smax). At first, a section of Tehran subway line 7 was modeled using the finite difference method (FDM). Then a dataset including 100 Smax values were prepared for creating the intelligent model. Among the intelligent methods, the gene expression programming (GEP) method was selected to represent the mathematical equation and the built numerical-intelligent model explained a proper performance. The determination coefficient, R2, for both the training and testing phases was 0.976 and 0.931, respectively. At the end, the derived mathematical equation from the GEP model was prepared using the visual basic (VB) in the form of predictor software. According to accuracy of the prediction results, the presented equation and software are reliable and suitable as an alternative for the numerical modelling.

Pre-analysis of the geometry and deviation of multiple hydraulically induced fractures is a decisive factor in the successful multiple hydraulic fracturing operations. Besides, fracture spacing should be optimal for obtaining desired results such as maintaining sufficient aperture for proppant placement, avoiding screen-outs and also preventing fracture closure or crossing multiple fractures. In fact, the final geometry and deviation of multiple hydraulic fractures are dramatically influenced by the interaction of multiple hydraulic fractures on each other known as stress shadow effect which is caused by fracture spacing and pore pressure change. Predicting the geometry and deviation of multiple hydraulic fractures is a challenging part of conducting this technology in Ilam reservoir due to low matrix permeability and naturally fractured nature of the reservoir. Accordingly, a fully coupled stress-diffusion XFEM model for initiation and propagation of multiple hydraulic fractures with five injection zones was prepared to optimize the effect of fracture spacing and pore pressure change on the multiple hydraulic fractures’ deviation and geometry. Additionally, the XFEM model was verified by three approaches including field data, Stress Intensity Factor and KGD zero toughness solution wherein a very good agreement with negligible error was obtained for SIF, field data and KGD M-vertex solution. However, this study has confirmed that both pore pressure and stress shadows contribute to change the fracture geometry and its deviation significantly in Ilam reservoir. Also, increasing pore pressure between fractures, may affect the fracture geometry to be tighter in width and shorter in length. In addition, considering optimized fracture spacing about 75 m resulted in creation of very smooth, uniform and deeper multiple hydraulic fractures; so, there will be no closed fractures in DPH-02 horizontal wellbore and the possibility of crossing the furthest fracture by the second fracture significantly reduced when the fracture spacing was higher than 5 m.

Ground vibrations induced by the blasting of explosives can cause damage to the slope stability of mines. The important indicators of rock mass such as the geological discontinuities, physical and mechanical properties of rock can affect the creation and prediction of blast damage. This paper aims to assess the simultaneous effects of the above properties. For that purpose, peak particle velocity as the indicator of damage at two rock slopes was examined through a three-dimensional distinct element code (3DEC). The developed model simulated the dynamic pressure of detonation and provided useful results for analysis. The qualitative analysis demonstrated how significant it is to incorporate the rock mass properties in the model. Moreover, a statistical analysis was performed to quantify the effects of these properties. Therefore, the distance from blast, dip/direction of discontinuities, blast damage factor (Hoek–Brown failure criterion) and Geological Strength Index have the most influences on the slope damage, respectively. The moment failure analysis of 3DEC explained the Shear–Tension and Shear–Shear failures associated with the rock mass damage caused by blasting. The dip/direction of discontinuities plays a major role in the control or propagation of dynamic pressure and should be considered in blast damage control. If necessary, artificial discontinuities such as pre-splitting should be employed for better control and use of the favorable effects of geological discontinuities.

Rock failure mechanism is one of the most important issues in rock mechanics engineering which plays a key role in the stability analysis of various structures. Therefore, different failure criteria have been proposed to understand the failure mechanism of rocks. One of the most commonly used rock failure criteria is the Hoek-Brown criterion, in which there is a parameter called mi, which is very important to the response provided by this criterion. Due to the importance of conducting extensive studies on this parameter, in this current research, by performing a series of experimental triaxial compressive strength test and numerical simulating in PFC-2D code, the effect of the Hoek-Brown constant mi on the failure mechanism and crack growth of different rocks has been studied. Based on the results of this study, it was found that the effect of parameter mi on the failure mechanism of different rocks varied according to the type of rocks, and the greatest effect of this parameter was on the peak strength of rocks. In addition, it was found that under higher lateral pressures, there are less destructive cracks in rocks, and as a result, they show more ductile behaviour., Mehanizam loma stijene jedno je od najvažnijih pitanja u mehanici i inženjerstvu stijena te je ključno u analizi stabilnosti raznih struktura. Za različite kriterije loma predloženi su različiti mehanizmi odgovorni za takav proces. Jedan od najčešće korištenih kriterija kojim se opisuje lom stijena jest Hoek-Brownov kriterij, u kojemu postoji varijabla zvana mi, koja je vrlo važna kod ocjene tim kriterijem. Zbog važnosti provođenja opsežnih studija o prilagođavanju te varijable u prikazanim istraživanjima ona je određena izvođenjem serije eksperimentalnih ispitivanja troosne tlačne čvrstoće i numeričke simulacije u PFC-2D kodu. Time je istražen učinak vrijednosti mi na lom stijene i rast pukotina različitih stijena. Na temelju rezultata utvrđeno je kako je utjecaj varijable mi na lom različitih vrsta stijena varijabilan, a najveći je učinak na vršnu čvrstoću stijena. Također, utvrđeno je da su pod većim bočnim pritiscima razarajuće pukotine u stijenama manje (uspoređeno s prethodnim testom), a kao rezultat pokazuju više duktilno ponašanja.

Rocks are formed from particles and the interaction between those particles controls the behaviour of a rock’s mechanical properties. Since it is very important to conduct extensive studies about the relationship between the micro-parameters and macro-parameters of rock, this paper investigates the effects of some micro-parameters on strength properties and the behaviour of cracks in rock. This is carried out by using numerical simulation of an extensive series of Uniaxial Compressive Strength (UCS) and Brazilian Tensile Strength (BTS) tests. The micro-parameters included the particles’ contact modulus, the contact stiff ness ratio, bond cohesion, bond tensile strength, the friction coefficient and the friction angle, and the mechanical properties of chromite rock have been considered as base values of the investigation. Based on the obtained results, it was found that the most important micro-parameters on the behaviour of rock in the compressive state are bond cohesion, bond tensile strength, and the friction coefficient. Also, the bond tensile strength showed the largest effect under tensile conditions. The micro-parameter of bond tensile strength increased the rock tensile strength (up to 5 times), minimized destructive cracks and increased the corresponding strain (almost 2.5 times) during critical stress., Svaka je stijena stvorena od čestica čijim se međudjelovanjem određuju njezina mehanička svojstva. Budući da je vrlo važno provesti opsežne studije o povezanosti mikroparametara i makroparametara stijene, u ovome su radu istraživani učinci nekih mikroparametara na svojstva čvrstoće i ponašanje pukotina stijene numeričkim simulacijama jednoosne tlačne čvrstoće (UCS) i brazilske vlačne čvrstoće (BTS). Ispitivani mikroparametri uključivali su kontakt čestica, omjer kontaktne krutosti, koheziju veze, vlačnu čvrstoću, koeficijent trenja i kut trenja, a mehanička svojstva stijene bogate kromitom bile su osnovne vrijednosti ispitivanih mikroparametara. Utvrđeno je kako su najvažniji mikroparametri na ponašanje stijene kod tlačenja kohezija veze, vlačna čvrstoća veze i koeficijent trenja. Također, vlačna čvrstoća ima najveći učinak u vlačnim uvjetima. Ovaj mikroparametar povećava vlačnu čvrstoću (do 5 puta), minimalizira destruktivne pukotine i povećava odgovarajuće naprezanje (gotovo 2,5 puta) pri kritičnome naprezanju.

Mechanical earth model is a numerical representation of the stress state, pore pressure and rock mechanical properties. While the different parameters in the MEM are interconnected in various ways, they fundamentally stem from the same basic set of log measurements. This paper demonstrates a scientific workflow to build a comprehensive well-centric MEM for a well in a carbonate reservoir in Persian Gulf and calibrate it via utilizing the existing data including LOT, MDT, drilling incidents, etc., to minimize the uncertainties related to data limitations. Finally, the calibrated MEM was used for sensitivity analysis of various wellbore trajectories and mud weight/pressure window for planning future wells and safe drilling in this underdevelopment field. Poroelastic modeling along with rigorous calibration indicates strike slip toward normal faulting stress regime. Also, shear wave anisotropy analysis results in N40E orientation for the maximum horizontal stress. The optimum mud weight for safe drilling was found to be 120 pcf for Gachsaran Formation, 105 pcf for all the formations from Asmari to Kazhdumi limestone and 85 pcf for all the formations from Yamama to total depth. On this basis, it is recommended to put the casing shoes at the base of Gachsaran, Kazhdumi limestone and final depth. The results recommend planning the future wells horizontally in the NE–SW direction for formations having SS stress regime and wells near vertically in formations having NF stress regime. Besides, the drilling safe mud window resulting from Mogi–Coulomb failure criterion is broader, while the Mohr–Coulomb is more limited.

Ground vibration is one of the most critical undesirable factors of blasting. In this study, the effects of the blast damage factor and blast design parameters in a rock slope through applying the dynamic blast loading on ground vibration are investigated. Modelings were conducted considering three major geological discontinuities with a spacing of 15 m and a 45 degrees dip relative to slope face. A 3D discrete element code (3DEC Version 5.2) was used for this purpose. The pressure-decay function was used to simulate the dynamic pressure of detonation. Peak particle velocity (PPV) was selected as the main indicator to evaluate the effects of each one of these parameters by utilizing FISH programming language. Therefore, the PPV values were recorded continuously from the blast hole collar to the end of the model. The effects of rock mass quality (which is affected by the reduction in blast damage factor) and the parameters of hole diameter, burden, and spacing, stemming length, and blast delay time on the PPVs are investigated. The obtained results from numerical simulation indicated that the blast damage factor has a significant effect on ground vibrations. Moreover, it was also found that delay time is less effective than other blast design parameters on ground vibrations.

The present study was conducted to investigate and modify the extensometer results in double-curvature arch dams. To evaluate extensometer results of Karun-4 dam, first, the distinct element 3DEC-D...

Dams constitute a potential hazard to downstream life and property. Therefore, it is necessary to detect any signs of abnormal behaviour in structural safety. Monitoring of an embankment dam plays ...

Due to ignoring the role of real topography in the numerical modeling carried out for back analysis and considering that in the tunnel longitudinal profile the distance of tunnel roof to the ground surface is the maximum, some results inaccuracy may occur. This issue is especially critical for cases when two tunnels or underground structures are constructed next to each other. The purpose of the present research is to study the role of real topography on the obtained results of back analysis and determine the accurate geomechanical parameters of the rock mass using back analysis based on convergencemeter data. For this aim, 8 instrumentation sections were modeled using FLAC3D 5.0 and the real topography was determined. Next, another numerical model was built to study the role of real topography and the obtained modeling results were compared for cases with and without real topography; where a significant difference was obtained between the results. In the case of ignoring real topography, the error function obtained from monitoring and numerical method results are between 1.5 and 10 times more than the case of considering real topography, suggesting the significant role of real topography. Furthermore, stability analysis and optimization of tunnels support system performed in this study using the real topography data. The results showed that removing the designed rock bolts the tunnel was still stable through other designed supports.

Uniaxial compressive strength and tensile strength considered as important parameters in characterization of rock material in rock engineering. The necessary core samples cannot always be obtained from weak and block-in-matrix conglomeratic rock. For this reason, the predictive models can employed for the indirect estimation of mechanical parameters. The study investigated correlations uniaxial compressive strength and tensile strength with point load index. Numerous specimens of weak conglomerate were collected from different sites of dams in Iran. Predictive models include regression techniques and artificial neural network. To control performance of prediction capacity of equation, root mean square error and correlation coefficients were calculated. The correlation coefficients indices were calculated as 0.96 for the uniaxial compressive strength obtained from the regression model and 0.94 obtained from artificial neural network model; 0.605 for the tensile strength obtained from the regression model and 0.638 obtained from artificial neural network model.

This paper deals with the control of ground surface settlement due to excavation of shallow tunnels. In order to control the settlement, one should be able to predict it, based on the prediction one may consider required preventions and protections. Prediction of surface settlement depends on several parameters and each parameter has an effect on the other. Application of the traditional methods could become impractical as the proposed equations might have low accuracy. To overcome these limitations, intelligent methods could be implemented. The present study aims to develop an intelligent model for prediction of the surface settlement in Shanghai subway line 2 project using adaptive neuro-fuzzy inference system (ANFIS). The results indicated that the proposed model had an appropriate performance. In order to perform sensitivity analysis of the ANFIS model, cosine amplitude method (CAM) was used and according to the results it was found that the operational, geometric and strength parameters had the highest impacts, respectively. Furthermore, amongst the input parameters, the two parameters of grout filling percentage (n) and grouting pressure (P) were identified as the most effective ones. The values of critical settlement were determined based on Rankin’s criteria of damage risk assessment to control the ground settlement. Then, the corresponding surface settlement was minimized by changing values of the input parameters. According to the results, control of machine operational factors particularly the n and P parameters had a crucial role in reducing surface settlement and preventing pertinent damages.

Since extensometers are used to determine the absolute deformation of foundation and abutments and all results are obtained in reference to the base rod, the accuracy of these results has been constantly a subject of debate. In this regard, locating and installing extensometers outside the range of effect zone is also another challenge. The main purpose of this paper is to investigate and modify extensometers results based on the mentioned issues. For this aim, the concrete RCC Zhaveh dam in Iran was selected as the case study. To study the results of extensometers installed in this dam, first, the 3DEC_DP 5.00 software was applied for numerical modeling. Parameters such as discontinuities, dead load and piezometric pressure in the interface of concrete and rock were considered. Next, using the results obtained from 6 extensometers in foundation and abutments and 4 clinometers in dam body, the numerical model was calibrated through back analysis method. The results indicate that the base rod is moved and is not recommended being used as the base point. In other words, because installation of base anchor outside the range of effect zone is not possible due to the operational and economic considerations, the obtained results are not accurate enough. The results indicate a considerable 2-3 mm displacement of the base rod (location of the base anchor) in reference to the real zero point location, which must be added to the base rod results.

Monitoring is the most important part of the construction and operation of the embankment dams. Applied instruments in these dams should be determined based on dam requirements and specifications. Instruments selection considered as one of the most important steps of monitoring plan. Competent instruments selection for dams is very important, as inappropriate selection causes irreparable loss in critical condition. Lack of a systematic method for determining instruments has been considered as a problem for creating an efficient selection. Nowadays, decision making methods have been used widely in different sciences for optimal determination and selection. In this study, the Multi-Attribute Decision Making is applied by considering 9 criteria and categorisation of 8 groups of geotechnical instruments. Therefore, the Analytic Hierarchy Process and Multi-Criteria Optimisation and Compromise Solution methods are employed in order to determine the attributes

Careful monitoring in the earth dams, to measure deformation caused by settlement and movement has always been a concern for engineers in the field. In order to measure settlement and deformation of earth dams, usually the precision instruments of settlement set and combined Inclinometer that is commonly referred to IS instrument, will be used. In some dams, because the thickness of alluvium is high and there is no possibility of alluvium removal (technically and economically and in terms of performance), there is no possibility to place the end of IS instrument (precision instruments of Inclinometer-settlement set) in the rock foundation. Inevitably, have to accept installing pipes in the weak and the deformable alluvial foundation that this leads to errors in the calculation of the actual settlement (absolute settlement) in different parts of the dam body. The purpose of this paper is to present new and refine criteria for predicting settlement and deformation in earth dams. The study is based on conditions in three dams with a deformation quite alluvial (Agh Chai, Narmashir and Gilan-e Gharb) to provide settlement criteria affected by alluvial foundation. To achieve this goal, the settlement of dams was simulated by using finite difference method with FLAC3D software and then the modeling results were compared with reading IS instrument. In the end, the caliber of the model and validate the results, by using regression analysis techniques and scrutinized modeling parameters with real situations and then by using MATLAB software and Curve Fitting Toolbox, a new criteria for the settlement based on elasticity modulus, cohesion, friction angle, density of earth dam and alluvial foundation was obtained. The results of these studies show that, by using the new criteria measures, the amount of settlement and deformation for the dams with alluvial foundation can be corrected after instrument readings and the error rate in reading IS instrument can be greatly reduced.

This study aims to predict ground surface settlement due to shallow tunneling and introduce the most affecting parameters on this phenomenon. Based on data collected from Shanghai LRT Line 2 project undertaken by TBM-EPB method, this research has considered the tunnel’s geometric, strength, and operational factors as the dependent variables. At first, multiple regression (MR) method was used to propose equations based on various parameters. The results indicated the dependency of surface settlement on many parameters so that the interactions among different parameters make it impossible to use MR method as it leads to equations of poor accuracy. As such, adaptive neuro-fuzzy inference system (ANFIS), was used to evaluate its capabilities in terms of predicting surface settlement. Among generated ANFIS models, the model with all input parameters considered produced the best prediction, so as its associated R2 in the test phase was obtained to be 0.957. The equations and models in which operational factors were taken into consideration gave better prediction results indicating larger relative effect of such factors. For sensitivity analysis of ANFIS model, cosine amplitude method (CAM) was employed; among other dependent variables, fill factor of grouting (n) and grouting pressure (P) were identified as the most affecting parameters.

A variety of 3D numerical models were developed based on hydraulic fracture experiments to simulate the propagation of hydraulic fracture at its intersection with natural (pre-existing) fracture. Since the interaction between hydraulic and pre-existing fractures is a key condition that causes complex fracture patterns, the extended finite element method was employed in ABAQUS software to simulate the problem. The propagation of hydraulic fracture in a fractured medium was modeled in two horizontal differential stresses ( $$\Delta \sigma$$ ) of 5e6 and 10e6 Pa considering different strike and dip angles of pre-existing fracture. The rate of energy release was calculated in the directions of hydraulic and pre-existing fractures ( $$G_{\text{frac}} /G_{\text{rock}}$$ ) at their intersection point to determine the fracture behavior. Opening and crossing were two dominant fracture behaviors during the hydraulic and pre-existing fracture interaction at low and high differential stress conditions, respectively. The results of numerical studies were compared with those of experimental models, showing a good agreement between the two to validate the accuracy of the models. Besides the horizontal differential stress, strike and dip angles of the natural (pre-existing) fracture, the key finding of this research was the significant effect of the energy release rate on the propagation behavior of the hydraulic fracture. This effect was more prominent under the influence of strike and dip angles, as well as differential stress. The obtained results can be used to predict and interpret the generation of complex hydraulic fracture patterns in field conditions.

One of the most important reasons for the serious damage of embankment dams is their impermissible settlement. Therefore, it can be stated that the prediction of settlement of a dam is of paramount importance. This study aims to apply intelligent methods to predict settlement after constructing central core rockfill dams. Attempts were made in this research to prepare models for predicting settlement of these dams using the information of 35 different central core rockfill dams all over the world and Adaptive Neuro-Fuzzy Interface System (ANFIS) and Gene Expression Programming (GEP) methods. Parameters such as height of dam (H) and compressibility index (Ci) were considered as the input parameters. Finally, a form was designed using visual basic software for predicting dam settlement. With respect to the accuracy of the results obtained from the intelligent methods, they can be recommended for predicting settlement after constructing central core rockfill dams for the future plans. Keywords: Settlement, Adaptive Neuro-Fuzzy Interface System (ANFIS), Gene Expression Programming (GEP), Visual Basic (VB)

This research studies the effect of gravel pack size on sand production by designing and manufacturing a machine and a numerical model to simulate sand and gravel pack. This machine and the numerical model make it possible to test different rock along with various fluids under different stress in order to simulate the production of sand and gravel pack.PFC3D software is applied to create this numerical model. The numerical model consists of sand from 0.22 to 1.1 mm and gravel pack from 3.5 to 4.76, 4.76 to 9.9 to 12.6 and 12.6 to 16.8 mm and the physical model holds gravel from 9 to 4.76 and 4.76 to 9.25. The results from modeling demonstrated that sand is produced the least in the numerical model using gravel from 3.5 to4.76 mm and sand is produced less in the physical model containing gravel pack ranging from 4.76 to 9 mm and the fluid left more output discharge. Moreover, the outcomes from physical modeling proved that as time drags on, the fluid production rate got reduced and then reached to a fixed amount after placing gravel pack. So, it is suggested that gravel pack from 9mm to 4.76mm is more suitable from the viewpoints of fluid production rate and prevention of sand production. Based on dimensional analysis and the results from numerical modeling in a condition without gravel pack, a relation is concluded to estimate sand production rate.

Pressuremeter is one of the most reliable geotechnical in situ tests to be utilized in estimating different soil properties. The main parameters that can be obtained from this test are soil deformation modulus. In general, the pressuremeter test is time-consuming and costly that requires suitable equipment and experienced operators. With these limitations, it is necessary to introduce models for indirect determination of the pressuremeter modulus (EPM). Based on the literature, various models and equations have been proposed to predict the modulus of pressuremeter; however, most of them are for fine-grained soils. In this paper, multiple linear regression (MLR), artificial neural network (ANN), and gene expression programming (GEP) have been used to design new relationships for prediction of the pressuremeter modulus. The main difference between this research and other studies is the use of 62 pre-bored pressuremeter tests results in cohesive and granular soils for training and testing models. The study area is in Tehran where soils show a variation from low plasticity clay to clayey gravel. The moisture content, depth of test, and grain size distribution of soils are considered as independent variables. Comparison of the predicted EPM with the actual modulus obtained from the pressuremeter tests indicates that the proposed relationships are able to estimate the pressuremeter modulus well. The results showed that the relationships obtained from nonlinear analyses performed by smart methods are more accurate and have less error in comparison to MLR method. Comparison of the coefficient of determination (R2) values and errors related to them in the testing phase show that the obtained results from the GEP method are more reliable than the ANN method. Also, sensitivity analysis revealed that the soil moisture content is the most effective parameter among the variables on the pressuremeter modulus.

With the increasing competition in global mineral markets, designers are attempting to drive down overall mining costs. The demands for steeper pit slopes have triggered developments in the field of modern and comprehensive slope design. Risk-based optimization techniques are one of the most challenging state-of-the-art solutions for enhancing conventional procedures. Recognizing risk aspects has a fundamental role in updating the methods. Considering geotechnical and mine planning issues, this study describes the consequences of varying slope angles on final pit walls. Twenty-three risk elements are introduced and discussed in four groups: economic, technical, strategic, and regulatory compliance. Related examples are given on the state of the elements, and possible ways to achieve them from overall slope optimization studies of the Sungun copper mine in Iran. The circumstances indicate that decisions on optimized slopes do not relate only to geotechnical studies, but that relevant consequences depend on the four groups. Evaluation of the elements can promote slope optimization based on the concepts of risk.

There are various methods to predict the settlement caused by shallow tunneling, with each method having particular strengths and weaknesses. However, the most important weakness of common methods is the failure to consider all parameters contributing into the settlement. Nowadays, earth pressure balance machines (EPBMs) are commonly applied for tunneling into soft grounds. In this tunneling method, many parameters affect resultant surface settlement, it difficult to estimate the settlement by traditional methods. Soft computing, however, can be devised to cope with such engineering limitations. The aim of this study is to evaluate the ability of the soft computing methods of neuro-genetic system (NGS), adaptive neuro-fuzzy inference system (ANFIS), and gene expression programming (GEP) to predict maximum surface settlement (S max) caused by tunneling in Shanghai Subway LRT Line 2 project. For this purpose, S max is considered as a function of geometric, strength and operational factors, with the factors combined using different methods to reconstruct different models. The results showed that the models with operational factors outperformed other models. Among tested methods, ANFIS and NGS presented the best and the worst forecasts, respectively. With respect to the results of this research, it can be said that, despite the fact that GEP had lower accuracy in comparison to ANFIS, it represented the most suitable method to estimate S max , because of providing useful mathematical equations.

A series of laboratory hydraulic fracture experiments was conducted on synthetic rock samples to investigate the mechanism of hydraulic fracture initiation and propagation of a pressurised wellbore in non-fractured and fractured reservoirs. To achieve this goal, the influence of pre-existing fracture (both on and far from the wellbore wall) and horizontal differential stress was investigated on the fracture initiation and propagation in different stress regimes. In reservoirs with no fracture due to the high stress concentration in surrounding rock of the well, the fracture initiation and propagation pressure are increased. In fractured reservoirs, the presence of pre-existing fracture on the wellbore wall reduced the effect of the original stress concentration around the wellbore, which led to a drastic decrease in the fracture initiation and propagation pressure. In the far-wellbore region by increasing dip and strike of the pre-fracture, the fracture propagation pressure was decreased when it intersect...

One of the important methods used by tunnel construction engineers to examine the design, construction safety factor, and tunnel boring procedures is convergence measurement. Larger convergences may lead to safety problems such as rock destruction, boring machines jamming, delays in projects, or even geological disasters, in which case convergence measurement is considered the best method. The goal of this research is introducing a new convergence criterion for water conveyance tunnel based on the data from 31 convergence measurement stations of the Chehel Chay water conveyance tunnel. To achieve this objective, three different methods including statistical (SPSS), artificial neural network (ANN) and numerical modeling (3DEC) have been used. Observation points are defined on the tunnel wall in a realistic numerical modeling to compare the convergence results. The results revealed the success of the artificial neural network and indicated that the network managed to estimate the test data with a high correlation coefficient.

Hydraulic fracturing decisions are closely tied to quantitative description of rock mechanical properties and in situ stresses in the subsurface. Geomechanics plays a critical role in successfully optimizing hydraulic fracturing, especially in different stress regimes. For those stress regimes that are not normal, the hydraulic fracture geometry is usually more complex and more difficult to predict and investigate. In this study, a particle flow code (PFC) has been developed to investigate and compare the hydraulic fracture geometry in different stress regimes. The results have demonstrated that hydraulic fracture geometry is closely tied to in situ stress conditions, whereas any change in a predominant stress regime from normal to reverse affects the hydraulic fracture geometry. Based on the developed PFC3D model, in a given fracturing pressure, the width and height of the induced hydraulic fracture in a normal stress regime is higher than a reverse stress regime, while the length of the hydraulic fracture in a reverse stress regime is greater than the normal stress regime. The results from this study can be applied in both planning and real-time decisions during hydraulic fracturing jobs to optimize the operation and prevent any job failure which will in turn affect the ultimate productivity.