Showing papers in "Geotechnical and Geological Engineering in 2019"
TL;DR: In this article, a parametric study is carried out to discover the relationship between some of the various vegetation species and different soil types as well as slope angles, and the results showed that the percentage of FOS increased due to the vegetation effects can reach up to 43% with slope angles ranging between 15° and 25°.
Abstract: Rapid infrastructure development in Malaysia especially in Selangor causes drastic change in landscape and clearing of more vegetated areas. This has gradually lead to slope instability problems that causes enormous loss affecting human lives, destruction of property and environment.
Thus, conservation practices by incorporating vegetation to enhance slope stability is much needed alternative to the conventional technique of stabilization. Limited studies had been done in discovering the effectiveness of vegetative covers in relation to slope and soil parameters. Hence, in this paper, a parametric study is carried out to discover the relationship between some of the various vegetation species and different soil types as well as slope angles. Conventional limit equilibrium methods are applied in the analysis considering the soil shear strength parameters, unit weight of soil, as well as slope geometry. Typical scenarios of cut-slope along highways in Selangor are simulated in order to obtain comparable results from the stability assessment by means of calculating the factor of safety. The modelling showed that shallow slip failure can be prevented when sufficient number of roots of a certain tensile force interact with the slip plane, increasing the overall factor of safety of the slope. The percentage of FOS increased due to the vegetation effects can reach up to 43% with slope angles ranging between 15° and 25°. Moreover, based on the parametric study, silty soils showed more significance in contributing to the increase in FOS when incorporating vegetation.
52 citations
TL;DR: In this paper, an improved immersing treatment method is developed to enhance MICP through multiple treatments with low cementation media concentration, which can improve the utilization of the media and increase the unconfined compression strength.
Abstract: Experimental immersing method is one of treatment methods to study the microbial induced calcium carbonate precipitation (MICP) that can improve engineering properties of sandy soil. Cementation media concentration and treatment frequency are two factors that can influence the effect and efficiency of MICP process in the immersing method. An improved immersing treatment method is developed in this study to enhance MICP through multiple treatments with low cementation media concentration. Experimental results show that repeated treatments under cementation media concentration of 0.25 M Ca, 0.5 M Ca, and 0.75 M Ca can improve the utilization of cementation media and increase the unconfined compression strength of MICP-treated specimens up to 6400 kPa. Meanwhile, the hydraulic conductivity of MICP-treated sand reduced from untreated of 0.14 cm/s to 0.001 cm/s after four MICP treatments. Dry density of MICP-treated sand increased with higher concentration of cementation media and more treatment times. At the cementation media concentration of 0.25 M Ca, the MICP process can be repeated up to 4 times with an efficient improvement of mechanical strength. When the cementation media concentration increased to 0.5 M Ca or 0.75 M Ca, the optimum MICP treatment times reduced to two due to the reduction of void ratio.
49 citations
TL;DR: In this paper, a comparative evaluation of logistic regression (LR), frequency ratio (FR), information value (IV), and weight of evidence (WoE) methods for landslides susceptibility assessment in Bouandas region, North of Setif (NE Algeria).
Abstract: The present study is focused on a comparative evaluation of logistic regression (LR), frequency ratio (FR), information value (IV), and weight of evidence (WoE) methods for landslides susceptibility assessment in Bouandas region, North of Setif (NE Algeria). Information about landslide inventory and 17 pre-defined causative factors were prepared from multiple sources. The four methods are used to derive the weighted value of causative factors along the study area. The results were validated using receiver operating characteristic and the areas under the curves obtained using the FR, LR, IV and WoE methods are 0.86, 0.84, 0.81 and 0.79, respectively. The landslide susceptibility map produced from FR model is proposed to be more useful for the study area. It could reveal the relative importance of different factors in explaining landslides, and it may assist engineers in land-use planning.
43 citations
TL;DR: Lower bound finite element limit analysis in conjunction with second-order cone programming is developed and employed to investigate the stability of retained soils behind underground walls with an opening in cohesive-frictional soils.
Abstract: Lower bound finite element limit analysis in conjunction with second-order cone programming is developed and employed to investigate the stability of retained soils behind underground walls with an opening in cohesive-frictional soils. In this study, two-dimensional plane strain condition is setup for modelling the problem while the lower bound solution of the problem is obtained by employing the finite element approach of lower bound limit analysis. The lower bound optimization problem is cast as the second-order cone programming, and is solved by a conic programming algorithm. For practical use, the results of lower bound solution are summarized in the form of dimensionless stability charts of the load factor that is a function of the cover depth ratio of opening, overburden stress factor and soil friction angles. Plastic yielding zones predicted from the lower bound analysis are discussed and examined for these dimensionless parameters while the computed lower bound solutions are validated with an existing solution. Finally, a closed-form approximate expression is developed for predicting the lower bound solution of the load factor for the problem with practical ranges of cover depth ratios of opening, overburden stress factors, and soil friction angles. New opening stability factors with respect to soil cohesion and unit weight as a function of cover depth ratios of opening and soil friction angles are presented.
43 citations
TL;DR: In this paper, the authors describe the testing procedures and apparatuses associated with rapid measurements of a complete SWCC of a residual soil as obtained from combined measurements using a small-scale centrifuge and dew point methods.
Abstract: Soil–water characteristic curve (SWCC) is an important unsaturated soil property relating the water content of a soil to soil suction and it is conventionally measured using Tempe cell, pressure plate and salt solution methods. However, these tests are tedious and time consuming. The SWCC measurements using fast and efficient methods are required for engineering designs such as excavation, slope protection, retaining wall and landfill cover designs. This paper describes the testing procedures and apparatuses associated with rapid measurements of a complete SWCC of a residual soil as obtained from combined measurements using a small-scale centrifuge and dew point methods. The SWCC test results obtained using these alternative methods were compared with the SWCC data from Tempe cell, pressure plate and salt solution methods. Shrinkage tests were carried out in this study to incorporate the volume change of soil into SWCC. The experimental data from all SWCC tests were evaluated using first order analysis with 95% confidence interval for determination of upper and lower bounds of SWCC. The analysis results showed that the SWCC data obtained from tests using small-scale centrifuge and dew point methods were in good agreement with those obtained from Tempe cell, pressure plate and salt solution methods. This indicates that the combination of small-scale centrifuge and dew point methods can be used to generate a complete curve of SWCC for the residual soil. In addition, the time required to perform SWCC tests using the alternative methods is shorter than the SWCC tests using the conventional methods.
40 citations
TL;DR: In this article, fly-ash-based geopolymer incorporating ground granulated blast-furnace slag (GGBFS) was used to stabilize kaolin clay at ambient temperature.
Abstract: This paper focuses on stabilisation of kaolin clay at ambient temperature using fly-ash based geopolymer incorporating ground granulated blast-furnace slag (GGBFS). Comprehensive experimental programme was conducted including soil plasticity, compaction, unconfined compressive strength, durability and leaching. These tests were followed by a microstructural analysis using scanning electron microscopy (SEM) technique. An optimisation study using several combinations of geopolymer ingredients was performed, and the role of GGBFS in enhancing the geopolymer-stabilised clay was evaluated. The results indicated that introducing partial replacement of class (F) fly-ash by GGBFS assists, when synthesised in certain ratios, in achieving strength properties of geopolymer-stabilised clay comparable to those of cement stabilised clay. Although a small percentage of geopolymer can improve the soil strength, a larger amount was essential to enhance the wetting–drying durability performance. Under freezing–thawing conditions, low durability performance was detected indicating retardation in the geopolymer reaction at low temperature. For simulated water infiltration, leaching of the activator from geopolymer-stabilised clay was a minor concern in relation to the gel formation and long-term strength gain. Finally, SEM results clearly demonstrated a clay fabric modification attributed to the inter-particle contacts and the corresponding bonding due to the gel formation and hardening.
36 citations
TL;DR: In this article, an experimental study is attempted to compare the resilient modulus (MR) and permanent strain values of untreated and lime treated soil, based on different percentages of lime and curing period.
Abstract: Subgrade soils play a major role in the proper functioning of pavements. They are subjected to repeated loads due to traffic and often subjected to moisture ingress during monsoon seasons. If the subgrade is expansive in nature, lime stabilization is commonly adopted to mitigate swelling and shrinkage. However, the behavior of lime treated expansive soil under the cyclic loading and effect of moisture ingress is not yet fully understood. The subgrade is generally characterized by the parameter Resilient Modulus (MR), which is determined under laboratory conditions. Considering these issues, an experimental study is attempted to compare the resilient modulus (MR) and permanent strain values of untreated and lime treated soil. The comparison is made based on different percentages of lime and curing period. The test results are finally used to analyze the behavior of lime treated soil in their in-situ stress states.
36 citations
TL;DR: In this paper, a regression analysis between the soil's index properties (liquid limit-LL, Plastic limit-PL and Plasticity index-PI), compaction characteristics (maximum dry density-MDD and optimum moisture content-OMC), percentage of particle sizes (gravel, sand and clay/silt) and CBR was performed along an ongoing roadway construction project where thirty-three soil samples were collected and transported to the laboratory for analysis.
Abstract: The California Bearing Ratio (CBR) is the most utilised parameter for dimensioning flexible pavements in tropical countries. Often this test is expensive, laborious and time consuming, and to overcome this, some regression analysis (single and multiple) was considered between the soil’s index properties (liquid limit-LL, Plastic limit-PL and Plasticity index-PI), compaction characteristics (maximum dry density-MDD and optimum moisture content-OMC), percentage of particle sizes (gravel, sand and clay/silt) and CBR. The study was carried out along an ongoing roadway construction project where thirty-three soil samples were collected and transported to the laboratory for analysis. Routine geotechnical tests were carried out and thereafter correlation and regression analysis were run on the obtained results to assess the relationship between these index properties, compaction characteristics and the experimental CBR obtained. The results of this analysis showed relatively fair coefficients of determination of R2 = 0.772 between CBR and MDD using single linear regression analysis and R2 = 0.841 between CBR and all the parameters using multiple linear regression analysis (MLRA). Though the MLRA improved the R2 from 0.772 to 0.841, the inclusion of additional properties results in a marginal increase of R2 indicative of weak correlators of CBR hence practically not cost effective for pavement design .
34 citations
TL;DR: In this paper, the effect of friction angle anisotropy on the limit pressure was considered and an iterative procedure was made to incorporate the effects of soil anisotropic.
Abstract: The limit load in stability problems in soils is often influenced by the inherent anisotropy. Accordingly, it can be more or less misestimated if an anisotropic soil is simply assumed as being isotropic. In this research, the static and seismic active and passive earth pressures of vertical retaining walls in anisotropic sands are investigated by the use of the lower bound limit analysis method in conjunction with the finite elements and linear programming optimization technique. In this regard, the effect of friction angle anisotropy on the limit pressure was considered. To do so, an iterative procedure was made to incorporate the effect of soil anisotropy. In the proposed iterative procedure, the friction angle was incrementally updated after each iteration. After sufficient iterations, a converged solution and a consistent field of friction angle is achieved which satisfy the convergence criteria of the direction of the major principal stresses and the limit load, as well as a stable stress field. It is worth mentioning that the pseudo-static approach was considered in order to apply the seismic condition. The results were compared with those found in the literature and some design charts were developed. Findings indicate that the passive earth pressure coefficient is much more influenced by the degree of anisotropy than the active earth pressure coefficient.
34 citations
TL;DR: The principal objective of the study is to examine the applicability of Extreme Learning Machine and Multivariate Adaptive Regression Spline models for predicting the bearing capacity of a pile embedded in cohesionless soil and comparing their respective performances.
Abstract: In recent time, there have been significant advances in the reliability based design to take care of variability and uncertainty in the pile design. The principal objective of the study is to examine the applicability of Extreme Learning Machine (ELM) and Multivariate Adaptive Regression Spline (MARS) models for predicting the bearing capacity of a pile embedded in cohesionless soil and comparing their respective performances. The models are developed using numerical analysis and conventional equations. A comparative study is made between reliability indices obtained by First Order Second Moment Method (FOSM) and MARS and ELM based FOSM. The performance was evaluated using various performance parameters.
33 citations
TL;DR: In this article, a two-phase data-driven framework to model the time-series groundwater level with spatial-temporal analysis and least square support vector machine is proposed, which is used for real-time ground water level prediction.
Abstract: Investigation of groundwater level is considered a prominent research topic for the study of underground hydrologic system. Due to the complexities of underground geological structure, the accuracy of real-time ground water level prediction is limited. In this study, a novel two-phase data-driven framework to model the time-series groundwater level with spatial–temporal analysis and least square support vector machine is proposed. Groundwater data collected from four monitoring sites in the northern region of United Kingdom is utilize in this study. In phase I, the time-series analysis is conducted to study the temporal characteristics of the groundwater. Based on the time-series analysis, least square support vector machine is performed to construct the prediction model to forecast the future groundwater level. In phase-II, the spatial correlation between the water levels in four sites are computed to construct a comprehensive model regarding the interrelation between the monitoring sites. Computational results illustrated the outperformance of least square support vector machine in predicting time-series groundwater levels compared with other state-of-arts machine learning algorithms. It has been demonstrated that the spatial–temporal model may serve as an applicable approach for the future research of groundwater resources.
TL;DR: In this article, compaction and strength characteristics test were investigated using three compactive efforts (i.e., British Standard light, BSL (standard Proctor), West African Standard, WAS or ‘intermediate) and British Standard heavy, BSH (modified Proctor).
Abstract: Laboratory studies on lateritic soil treated with up to 8% calcium chloride (CaCl2) by dry weight of soil was carried out to establish the soil improving potential. Tests carried out include Atterberg limits and linear shrinkage, compaction characteristics (maximum dry density, MDD and optimum moisture content, OMC), strength characteristics (unconfined compressive strength, UCS and California bearing ratio, CBR) and microanalysis. Compaction and strength characteristics test were investigated using three compactive efforts [i.e. British Standard light, BSL (standard Proctor), West African Standard, WAS or ‘intermediate’ and British Standard heavy, BSH (modified Proctor)]. Results obtained show that Atterberg limits decreased with increased calcium chloride content. MDD increased with a corresponding decreased OMC of the soil–CaCl2 mixtures for the three compactive efforts. Peak UCS and CBR values were obtained at 4% CaCl2 content with increasing compactive effort. Microanalysis using Scan Electron Microscope, SEM shows the transformation of surface morphology at the edges of clay particles. Statistical analysis of result shows that CaCl2 content had significant influence on the Atterberg limit parameters and both the variations of CaCl2 content and compactive effort had significant effect on the strength parameters, maximum dry density as well as the optimum moisture content. The R2 values of regression models show that CaCl2, LL, MDD, OMC and CE have considerable influence on the UCS at 7 days curing and CBR values. Peak strength values are below those recommended for sub base and base stabilization, hence CaCl2 is not convenient as a stand-alone stabilizer but can be adequate as a modifier or as admixture in Cement or lime stabilization of lateritic soil.
TL;DR: In this paper, the potential of four popular artificial intelligence techniques (random forest, Gaussian process, M5P tree and artificial neural network) for estimating the strength of stabilized dispersive soil with cement clinker and fly ash was assessed.
Abstract: In this study, the potential of four popular artificial intelligence techniques random forest (RF), Gaussian process (GP), M5P tree and artificial neural network (ANN) are assessed for estimating the strength of stabilized dispersive soil with cement clinker and fly ash. GP, M5P and ANN models were providing a good estimate of performance, whereas the RF model outperforms them. For this study, a dataset containing 52 observations obtained from the laboratory experiments. Total data set (52 observations) has been segregated in two different groups. The larger group (36) was used for model development and the smaller group (16) was used for testing the models. Input dataset consists of dispersive soil (%), cement clinker (%), fly ash (%) and curing time (days), whereas unconfined compressive strength (UCS) of soil (MPa) was taken as a target. Sensitivity testing results conclude that the curing time is the most essential factor in estimating the strength of dispersive soil with cement clinker and fly ash for RF-based modelling. The results of this study also suggest that the combined mix of cement clinker and fly ash are used to increase the UCS of dispersive soil than an alone mix.
TL;DR: In this article, a series of ordinary triaxial shear tests, direct shear test and dynamic triaxials were performed on dense dry sand-rubber tire shred mixtures for various rubber replacement levels such as 0, 10, 30, 50 and 100% by weight.
Abstract: This paper deals with the characterization of dry sand-rubber tire shred mixtures to find shear strength and dynamic properties. A series of ordinary triaxial shear tests, direct shear tests and dynamic triaxial tests were performed on dense dry sand-rubber tire shred mixtures for various rubber replacement levels such as 0, 10, 30, 50 and 100% by weight. The effects of rubber content, confining pressures and rates of shearing on the angle of internal friction of the mixtures were investigated. Also, the influence of rubber content and the rate of horizontal displacement on the volumetric strain is presented. In addition, this paper proposes an appropriate method to find the angle of repose of dry sand-rubber tire shred mixtures. The angle of repose of the mixtures is compared with the angles of internal friction obtained from triaxial shear and direct shear tests. Finally, the effects of saturation, rubber content, axial strain, frequency and number of cycles of loading on the strain-dependent stiffness and damping properties of these mixtures were studied.
TL;DR: By contrasting the performance of various models based on k-nearest neighbors, naive Bayes, random forest, artificial neural networks (ANN), and support vector machines (SVM), it is uncovered that SVM and ANN were better for widespread application in geological surveys and construction acceptance to predict RCS accurately.
Abstract: The traditional method to estimate rock compressive strength (RCS) in field operation is dependent on hammering rocks and artificial identification. It is too subjective to get high estimation accuracy. For this reason, the new and non-destructive method uses machine learning algorithms to analyze acoustic characteristics of geological hammer to predict RCS accurately. The hammering sound samples were successively preprocessed by signal enhancement algorithm and double-threshold method to reduce noise and acquire valuable intervals of all. We have also performed the time-frequency domain conversion on sound signal through FFT, which obtained two brand new indexes, amplitude attenuation coefficient and high and low frequency ratio, as the input parameters of models. By contrasting the performance of various models based on k-nearest neighbors, naive Bayes, random forest, artificial neural networks (ANN), and support vector machines (SVM), we uncovered that the prediction accuracy of both SVM and ANN was over 95%, superior to others. Thus, SVM and ANN were better for widespread application in geological surveys and construction acceptance to predict RCS accurately. In addition, characteristic mechanism of acoustic spectrum was explained from microstructure, energy dissipation and filter effect, which indicated why there existed strong correlation between acoustic characteristics and RCS. The current rock mass classification standard was supplemented with the above two characteristic indexes for better identification.
TL;DR: In this article, the 3D stability of geocell-reinforced slopes was investigated using strength reduction method (SRM) in the presence of geocells and their infill and surrounding soils.
Abstract: Widespread application of geocells in practice, especially in slope stabilization, is mainly derived from the strengthening features they display in excess of membrane effect of planar geosynthetics. On the ground where geocells are in the shape of honeycombs, a three dimensional model and analysis provides a relatively more precise insight into the behavior of structures reinforced with them compared to the prevalent 2D means of slope stability analysis or methods taking the geocell layer as an equivalent soil layer. The three dimensional stability of geocell-reinforced slopes was investigated using strength reduction method (SRM) in the present paper. Both the geocells and their infill and surrounding soils were taken into account. Since ABAQUS is not provided with built-in ability of analysis by SRM, a SRM stepped procedure was adopted herein to determine FS by this finite element software. As the next step, using the aforementioned techniques, effects of some leading factors contributing to the stability of geocell-reinforced slopes such as geocell placement, pattern of multilayer reinforcement and number of geocell layers were evaluated thoroughly. Reliability of the applied stepped SRM procedure was verified in advance using the available results of a previously 3D- SRM slope stability analysis.
TL;DR: In this paper, a genetic algorithm technique, integrated with a numerical model (finite element method), was used to compute the optimal cut-off location and angle of inclination for barrages constructed on homogenous anisotropic soil foundations.
Abstract: A genetic algorithm technique, integrated with a numerical model (finite element method), was used in this study to compute the optimal cut-off location and angle of inclination for barrages constructed on homogenous anisotropic soil foundations. The exit gradient function is minimized as an objective function in the problem formulation. Constraints included uplift pressure functions and safety factors taking account of a minimum concrete floor thickness. Various degrees of anisotropy and different values of a range of heads have been studied. Around 1400 different situations (cases) were simulated using SEEP2D GMS software. Statistical nonlinear regression models were used to predict the pressure head and exit gradient for anisotropic soil foundations under various degrees of inclination (θ), relative location (b1/b) and relative depth (d/b). A genetic algorithm optimization model was also performed using Matlab. The study results indicated that the computed optimum cut-off locations and relative inclination angles were affected by changing the anisotropic ratio and relative cut-off depth. For isotropic soil foundations, for cases with a cut-off ratio (d/b) of up to 0.4, the optimum inclination angle ranged between 59° and 68° for upstream locations. In other relative cut-off depth cases, the cut-off can work efficiently when situated in the last third of the concrete floor foundation, this considered the optimum location. For anisotropic soil, optimum locations tended to be upstream for most d/b values.
TL;DR: In this paper, the authors investigated the correlations between the physical and mechanical properties and geostatistical analysis of the shale rock based on the experimental data and the data collected from various research studies.
Abstract: This study was focused on investigating the correlations between the physical and mechanical properties and geostatistical analysis of the shale rock based on the experimental data and the data collected from various research studies. In this study, over 250 data were used to characterize the shale rock behavior. The compressive strength and tensile strength of the shale rock investigated varied up to 200 and 13 MPa respectively. The shale rock was characterized based on the density, modulus of elasticity, fracture toughness and tensile strength and correlating the properties to compression strength and pulse velocity. Based on the statically analysis, the density of shale was in the range of 1.70–2.78 gm/cm3. Vipulanandan correlation model was effective in relating the modulus of elasticity, pulse velocity, fracture toughness with the compressive strength of the rocks. There was no direct correlation between the compressive strength and density or tensile strength and density of the shale rock. The new Vipulanandan failure model has been used to not only better quantify the tensile strength but also to predict the maximum shear stress of the rock. The prediction of the Vipulanandan failure model for shale rock type was also compared to the Mohr–Coulomb failure model. The Vipulanandan failure model has a maximum shear stress limit were, as the Mohr–Coulomb failure model did not have a limit on the maximum shear stress. Based on the Vipulanandan failure model the maximum shear stresses produced by the shale was 103 MPa. Based on the coefficient of determination (R2) and the root mean square error values, the Vipulanandan failure model predicted the results better than the Mohr–Coulomb model.
TL;DR: In this article, the authors established the horseshoe-shaped roadway model by particle flow code firstly and then analyzed the roadway damage process through the contact force chain, deformation displacement and distribution of micro-cracks.
Abstract: Deformation and destruction of roadway surrounding rock is one of the main causes of coal mine accidents. In this paper, the horseshoe-shaped roadway model was established by particle flow code firstly and then analyzed the roadway damage process through the contact force chain, deformation displacement and distribution of micro-cracks. The research result show that the parallel bond model can well simulate the damage process of the coal mine roadway. The surrounding rock can be divided into four zones from the roadway side to the deep rock mass. The micro-contact force chain is the force transmission path and the principal stress is the macroscopic reflection of the micro-contact force chain.
TL;DR: In this paper, the 12/4, 11/3 and 8/4 band ratios combination was adopted to discriminate the different lithologies and the directional filters were applied to undertaken the lineamentary mapping.
Abstract: Detailed geologic mapping provides valuable informations about the spatial distribution of lithological outcrops and lineaments; required to carry out the necessary investigations of the geologic, geotechnical and hydrogeological data investigation. The unavailability of geologic coverage at meduim scale in the Nementcha mountains has severely hampered geoscientist to develop and test their hypotheses. In order to exploit multispectral datasets for the characterization of surface materials; Sentinel-2A data was used in the discrimination of geological classes along Youks les Bain area, extreme NE of Algeria. Resampling, orthorectification, atmospheric correction, and radiometric normalization have been applied to the Sentinel-2A radiance data, identified as the first and most important step in processing. The 12/4, 11/3 and 8/4 band ratios combination was adopted to discriminate the different lithologies. Then, to reduce redundant information in highly correlated bands, the principal component analysis has been implemented. The directional filters were applied to undertaken the lineamentary mapping. At last the project was exported and processed in GIS spatial database. The result allows the discrimination of the lithological boundaries and help to a better understanding of the local geology of the study area. The project digital databases represents a key tool to support research activities in the West of Tebessa region.
TL;DR: A particle swarm optimization based MATLAB code is developed to search for critical failure surface (CFS) with minimum factor of safety (FOS) of any slope by minimizing the objective function.
Abstract: Searching for critical failure surface (CFS) with minimum factor of safety (FOS) of any slope require application of optimization. A particle swarm optimization (PSO) based MATLAB code is developed to search for CFS and associated minimum FOS of slopes by minimizing the objective function. The FOS against slope failure is determined by Bishop’s method based on limit equilibrium technique, which also serves as the objective function. With this goal, another computer code is developed in MATLAB to solve non-linear nature of equation of FOS. The effectiveness of developed code is investigated through study of different parameters such as swarm size, iteration count and slice numbers etc. The applicability of PSO is evaluated for homogeneous and layered slopes considering the effect of seepage and seismic loading.
TL;DR: In order to solve the problem of variation degree of water inrush factors in floor, the geological data of No 315 mining area in Huatai Coal Mine were taken as engineering background Entropy weight method (EWM) was combined with variation coefficient method (VCM) to construct the comprehensive weighting vulnerability index model to determine the weight of each factor.
Abstract: In order to solve the problem of variation degree of water inrush factors in floor, the geological data of No 315 mining area in Huatai Coal Mine were taken as engineering background Entropy weight method (EWM) was combined with variation coefficient method (VCM) to construct the comprehensive weighting vulnerability index model to determine the weight of each factor At the same time, the weighted value was combined with the geographic information system to draw the risk zoning map of floor water inrush to predict the risk of floor water inrush The results show: (1) fault fractal dimension is used to increase the accuracy of prediction of floor water inrush and easy to calculate (2) The combination of EWM and VCM can weaken the influence of abnormal indexes and make the weighting results more real and reasonable (3) Compared with the method of water inrush coefficient, the prediction result of the vulnerability index model with comprehensive weight is more accurate, which beneficial for Huatai coal mine safety production
TL;DR: In this article, a crack image processing software was used for the dynamic and quantitative measurement of the development of surface cracks in expansive soils with different compaction degree under the condition of dry-wet cycles.
Abstract: Expansive soil is a typical multi-crack soil, and the stability of expansive soil slope is significantly affected by cracks. In this study, pores (particles) and crack image analysis system (PCAS), a crack image processing software was used for the dynamic and quantitative measurement of the development of surface cracks in expansive soils with different compaction degree under the condition of dry–wet cycles. Furthermore, the shear strength of expansive soil with different degree of crack development was also tested. The test results showed that the greater the compaction degree, the smaller the cracking degree. The cohesion decreased with the increase of dry–wet cycles; however, the internal friction angle was less affected. For the same number of cycles, cohesion increased with the increase of the compaction degree. The relationship between the cohesion and the crack parameters including the number of crack joints, number of cracks, total length of cracks, and average width of cracks exhibited similar trends. This indicates that cohesion has some relevance with these crack parameters. The crack rate and fractal dimension exhibited linear relationship with cohesion. The research results provide an important basis for the application of crack parameters to calculate the strength parameter of expansive soil in engineering field.
TL;DR: In this paper, a comprehensive multi-factor prediction model was established to predict the rockburst intensity of evaluation objects and forecast the development trend of rockburst from dynamic prediction using set pair analysis theory.
Abstract: Rockburst is an extremely complicated dynamic instability phenomenon. It is one of the common rock mechanics problems in high geostress areas. The accuracy of the rockburst tendency prediction is generally restricted by the evaluation factor or method. In this study, the set pair analysis theory is used to optimize the identification criteria of attribute in unascertained measure theory. Combined with the information entropy theory, a comprehensive multi-factor prediction model was established to predict the rockburst intensity of evaluation objects and forecast the development trend of rockburst from dynamic prediction. The turchaninov criterion (σθ + σL)/Rc, the russenes method σθ/Rc, the strength brittleness coefficient B, the elastic strain energy Wet and the rock quality designation RQD were presented to constitute comprehensive evaluation multi-factor. The proposed model was used in the Dawoshan Tunnel of Jinwen Railway which was divided into six sections with different lithology areas. The evaluation factors require to collect geostress parameters of the tunnel at different buried depths and the mechanical parameters of rock mass. All parameters can be obtained by carry out the field geostress test and laboratory testing. By doing so, the affiliated grade of rockburst intensity can be identified. The results of presented prediction model showed the high accuracy and practicality. It is a meaningful discovery for researching rockburst tendency prediction.
TL;DR: A review of uncertainty and uncertainty analysis methods, problems and developments in geotechnical modelling of rock slope stability is provided in this article, with a simple survey of probability-based reliability methods that have been used for rock slope assessment problems.
Abstract: The stability analyses of slope excavations in rock mass require reliable geomechanical input parameters such as rock mass strength, friction angle and cohesion of sliding surface. These parameters are naturally uncertain and their exact values cannot be known, therefore, their variability must be properly accounted for in the stability analyses. Deterministic approaches such as the limit equilibrium methods, numerical methods and kinematic analysis methods do not account for the variability in any of the input parameter. This paper therefore provides a review of uncertainty and uncertainty analysis methods, problems and developments in geotechnical modelling of rock slope stability. The review is motivated by the availability of qualitative and number of methods for uncertainty analysis. The paper examines the various definitions and description of uncertainty and the different vocabularies that are used, and also summarises and categorises the different sources of uncertainty as well as integrating uncertainty for rock slope assessment problems. The paper discussed a simple survey of probability-based reliability methods that have been used for rock slope stability analysis in the past 3 decades.
TL;DR: In this paper, a study on the technology of directional fracturing blasting for pressure relief of dynamic pressure roadway is presented, which shows that directional fracture blasting have obvious effect of joint formation, and the effect of pressure relief is remarkable, effectively controlling the deformation of surrounding rock under dynamic pressure.
Abstract: Affected by mining activities, 3−1103 tailgate of Hongqinghe coal mine is seriously deformed. The floor of tailgate cracking and tilting, and two ribs appearing in the net bag, which affects normal transportation and pedestrians. To solve this difficulty, this paper study on the technology of directional fracturing blasting for pressure relief of dynamic pressure roadway. First of all, taking method of theoretical analysis, the mechanical mechanism of directional blasting and the relevant calculation formula are expounded. Afterwards, the mechanical model of roof cutting of roadway is established. In order to analyze the evolution and propagation of effective stress, directional blasting model is established by using LS-DYNA numerical calculation software. In the next part, the roof control technology of directional cut blasting is put forward. In the end, the blasting effect is observed, and the deformation of the roadway before and after pressure relief is monitored and analyzed. The results shows that directional fracture blasting have obvious effect of joint formation, and the effect of pressure relief is remarkable, effectively controlling the deformation of surrounding rock under dynamic pressure.
TL;DR: In this article, a case study of the interaction between a slow-moving landslide in clay soil and a railway tunnel protected by sheet pile walls, that crosses the landslide accumulation is presented, where the role of the landslide slip surface depth, changing in the directions longitudinal and transversal to the tunnel, and of structural connections, affecting the pile-tunnel system response, are accounted for in detail.
Abstract: This paper reports a case study of the interaction between a slow-moving landslide in clay soil and a railway tunnel protected by sheet pile walls, that crosses the landslide accumulation. The earthflow, that develops in the Southern Apennines, Italy, has been long studied and monitored by different organizations, such as the national railway company and the University of Basilicata. Since the investigated landslide and construction typologies are quite diffused in mountainous areas, the case study can be considered representative of a large number of other similar cases. Differently from other approaches proposed in the literature, the role of the landslide slip surface depth, changing in the directions longitudinal and transversal to the tunnel, and of structural connections, affecting the pile–tunnel system response, are accounted for in detail. Several numerical models are used to simulate the interaction between the sliding soil and tunnel. Different 2D and 3D geotechnical and structural models are adopted to reproduce stress–strain scenarios compatible with the experimental evidence. The modeling results indicate that the interaction varies considerably along the tunnel length because of the 3D geometry of the landslide, and is conditioned by the residual shear strength available on the slip surface. The expansion joints in the tunnel lining only marginally influence the stress in the structure because of the presence of the adjacent sheet pile walls, which enable considerable collaboration between the tunnel sectors.
TL;DR: In this article, a Bayesian approach is developed for probabilistic characterization of mi, using information from guideline chart, regression model and site-specific uniaxial compression strength (UCS) test values.
Abstract: The Hoek–Brown constant mi is a key input parameter in the Hoek–Brown failure criterion developed for estimating rock mass properties. The Hoek–Brown constant mi values are traditionally estimated from results of triaxial compression tests, but these tests are time-consuming and expensive. In the absence of laboratory test data, guideline chart and empirical regression models have been proposed in the literature to estimate mi values, and they give a general trend of mi. Instead of only using either the guideline chart or regression models, information from both sources can be systematically integrated to improve estimates of mi. In this study, a Bayesian approach is developed for probabilistic characterization of mi, using information from guideline chart, regression model and site-specific uniaxial compression strength (UCS) test values. The probabilistic characterization of mi provides a large number of mi samples for conventional statistical analysis of mi, including its full probability distribution. The proposed approach is illustrated and validated using real UCS and triaxial compression test data from a granite site at Forsmark, Sweden. To evaluate the reliability of the proposed method, mi values estimated from the proposed method are compared with those predicted from a separate analysis which uses triaxial compression tests data. In addition, a sensitivity study is performed to explore the effect of site-specific input on the evolution of mi. The approach provides reasonable statistics and probability distribution of mi at a specific site, and the mi samples can be directly used in rock engineering design and analysis, especially in Hoek–Brown failure criterion to predict rock failure.
TL;DR: In this paper, the average strength of sandstone under uniaxial cyclic loading and unloading tests of equal amplitude loading with four loading rates were conducted on sandstone samples using the testing system of MTS 815.03.
Abstract: In this paper, uniaxial cyclic loading and unloading tests of equal amplitude loading with four loading rates were conducted on sandstone samples using the testing system of MTS 815.03. The evolution characteristics of stress–strain, peak stress and macro-failure characteristics of sandstone under uniaxial cyclic loading and unloading tests with four equal amplitude loading rates were analyzed. The average strength of sandstone under uniaxial cyclic loading and unloading is less than that under uniaxial compression. And with the increase of loading rate, the peak stress of sandstone nonlinearly increases and its strength dispersion decreases gradually. Moreover, the hysteretic loop of stress–strain curve under uniaxial cyclic loading and unloading has a continuous “migration” phenomenon. When close to failure, the lateral strain will suddenly increase and the strain recovery is small when unloading. The failure of sandstone is the single shear failure at a low loading rate and gradually transformed into splitting ejection failure with the increase of loading rate. The “expansion” phenomenon of sandstone represents that it enters the accelerated failure stage. The larger the loading rate is, the smaller the volume compression before critical points is. After post-peak, the greater the loading rate is, the intenser the volume expansion is. According to above achievements, the failure of the rock can be speculated by monitoring the lateral deformation of rock or lateral strain rate in practical engineering.
TL;DR: In this paper, a shed-scaffold system of pipe roof and steel grating is proposed to improve tunnel stability in Tianhengshan highway tunnel and Haide highway tunnel in China.
Abstract: Pipe roof system is widely used in the shallow tunnel as the support system. Although the diameter of pipe roof is diversity, the pipe roof system of small diameter pipe roof and small spacing steel grating is widely adopted in China. The stability mechanism of that pipe roof system is to form shed-scaffold system. In that shed-scaffold system, the function of pipe roof is to form micro-soil-arch in overlying soils between the pipes and to transmit the excavation loads. The steel gratings are the main bearing structure. To form the shed-scaffold system effect, three stabilities, stability of soils between pipes, stability of tunnel working face and stability of tunnel foundation, should be satisfied simultaneously. On that basis, the collapse accidents of Tianhengshan highway tunnel and Haide highway tunnel in China are analyzed. It shows that the stability of tunnel foundation would be overlooked easily and causes even overall collapse. At last, the measures to improve the stability are proposed.