Search

In-situ testing programs are conducted to evaluate the potential use of the light weight deflectometer (LWD) device for measuring the in-situ deformation modulus of subgrade soil layers stabilized with geosynthetic reinforcement. A series of in-situ field tests are carried out on six test sections that include 1) unstabilized subgrade soil and 2) geogrid- and geocell-reinforced stabilized subgrade soil. Field measurements on the modulus improvement factor (MIF) of stabilized subgrades provide more practical and realistic results. The MIF value depends on the type, geometry, location of geosynthetic reinforcements, and characteristics of subgrade soil. An accurate and quick evaluation of MIF can help in the timely design and execution of new road networks. The novelty of the study comprises of measuring the in-situ MIF of geosynthetic stabilized subgrade soil using a light weight deflectometer (LWD) device and comparing the results with the in-situ plate load test (PLT) and falling weight deflectometer (FWD) devices for the considered test configurations. The deformation modulus from LWD test demonstrated a similar trend to the modulus values obtained from PLT and FWD. The improved in-situ deformation modulus from three different tests (EPLT, ELWD, and EFWD) are found to be 29.5 MPa, 34.5 MPa and 114.8 MPa for geocell; 21.1 MPa, 25.7 MPa and 86.2 MPa for biaxial geogrid; 37.2 MPa, 29.7 MPa and 89.5 MPa for triaxial geogrid, when the geosynthetic reinforcement is embedded at a depth of 100 mm. In addition, the MIF values of geosynthetic stabilized subgrade soil for the considered test sections are found to be in the range of 1.0 to 2.5. [ABSTRACT FROM AUTHOR]

The different methods for computing the deformation modulus of in-situ soils based on the pressuremeter test have been advised in the current standards and handbooks. The suitability of these suggested methods for variable soil layers in different areas still need to be investigated. The numerical model is established for determining the in-situ deformation modulus of soils based on the results of pressuremeter tests using the ABAQUS finite element software, in which the geostatic balance is considered. The size of the model, lateral pressure coefficient and horizontal radial stress are identified to be the critical parameters for simulating the pressuremeter tests. The parameter sensitivity analysis on these critical parameters is done in detail. Based on the results of the sensitivity analysis, the numerical model has been simplified. Furthermore, the true deformation modulus of foundation soils is determined by an inversed method based on the measured pressuremeter curves. The deformation moduli using the recommended methods from the standards and handbooks is compared to the true ones. The discrepancy among the different methods on determining the deformation modulus have been explored. The suggestions on accurately determining the in-situ deformation modulus have been given based on the pressuremeter tests which offer reference for the engineering design. [ABSTRACT FROM AUTHOR]

In this research, rock mass deformation modulus (Emass), classification of rock mass, cohesion (c) and internal friction angle (Φ), and intact rock properties of the Khersan 2 dam site were investigated. Factors affecting mechanical properties were investigated and compared with the results of previous studies. To assess the shear strength and the Hoek and Brown failure criteria parameters, the triaxial test was performed on samples under saturated conditions. The Q-system and rock mass rating (RMR) were calculated for five-metre sections of boreholes. Results of the Mohr–Coulomb failure criterion showed that the limestones have a mean Φ of 40 degrees and a mean cohesion of 1 MPa, marl limestones have an average of 30 degrees and cohesion of 0.50 MPa, and anhydrite and gypsum showed an average of 26 degrees and 0.10 MPa. The results showed that c and Φ increase with the increase in the shear box size. Based on the RMR and Q-system the site was classified in good class. The mean of Emass showed that the dilatometry test gives the lowest value. Linear and logarithmic relationships were established between RMR89 with compressional wave velocity (Vp) (R2 = 0.95 and RMSE = 1.63) and Q-system (R2 = 0.95 and RMSE = 2.05), respectively. [ABSTRACT FROM AUTHOR]

To broaden the sources of earthwork and the utilization of soda residue (SR) and fly ash (FA), SR, FA, and clay were mixed to form a soda-residue soil (SRS) by adding externally moderate content of lime or/and cement for further stabilization. Through the orthogonal scheme, 9 groups of proportions were designed. Subsequently, the unconfined compressive strength (UCS) at different curing ages was conducted. Afterward, the stress–strain pattern, the UCS and water absorption, the sensitivity of factors and levels to UCS, and the deformation modulus were analyzed. Finally, the enhancement mechanism of SRS from physicochemical reactions was explored by analyzing gradation and microstructure. The results show that the patterns of stress–strain curves on SRS at different curing ages are similar; all have obvious stress peaks, and the specimens of SRS present a brittle failure. With the extension of curing ages, the UCS of all proportions increased; the UCS of the G2 group increased the most, reaching 85.44%, and the G9 group increased the least, only 1.92%. However, the water absorption quality decreased, and G6 decreased the most (37.53%), G7 decreased the least (0.84%), and UCS and water absorption quality showed a negative correlation. The sensitivity of each factor to UCS was different; the SR was the most sensitive at 7 d, but the lime was the most sensitive at 28 d. The sensitivity of each factor level (content) to UCS remains unchanged at different curing ages. There is a linear relationship between the deformation modulus and UCS. The analysis demonstrates that the better strength properties of SRS are mainly determined by the superior gradation and the reaction of materials. [ABSTRACT FROM AUTHOR]

The deformation characteristics of rocks are of vital importance in addressing most geomechanical issues as they are one of the most critical input parameters in rock engineering analyses. For this reason, robust forecasting models are required when analysing the stability of tunnels, slopes, mine galleries, and other underground excavations. In this research, novel predictive models are proposed to estimate the tangential Young modulus (Eti) of weak rocks. To achieve this, an extensive literature review is performed to obtain a comprehensive database including critical physico-mechanical properties of various weak rocks. Thanks to the advantages of soft computing methods such as genetic algorithm (GA), adaptive neuro-fuzzy inference system (ANFIS), artificial neural networks (ANN) and multivariate adaptive regression splines (MARS), novel predictive models are established. The effectiveness of the developed predictive models is investigated using various statistical measures and it is concluded that empirical models utilizing ANN and ANFIS methodologies are the most effective tools for estimating the Eti of weak rocks. In addition, a practical design chart is also developed for assessing the Eti of weak rocks. [ABSTRACT FROM AUTHOR]

Rock deformation modulus is one of the key parameters for the design and construction of underground rock engineering. Obtaining accurate rock deformation modulus is crucial for a comprehensive analysis of the deformation behavior of the surrounding rock in deep rock engineering. To achieve this goal, the commonly used methods for calculating rock deformation modulus are systematically sorted out and summarized. Furthermore, the rock deformation modulus is inverse-calculated by simulating in-situ tests using the finite element method, and the results are verified and analyzed by comparing them with the in-situ test results. For the actual project of deep shaft, a numerical calculation model is established to conduct an inversion analysis of rock deformation modulus of different lithologies in the deep strata. Additionally, a sensitivity analysis is performed on different strength criteria, Poisson's ratio and rock cohesion on rock deformation modulus. Finally, the numerical simulation inversion results are compared and discussed with the empirical formula calculation results. The results show that the values of rock deformation modulus obtained from numerical inversion using finite element method are in good agreement with those calculated based on the experimental rigid plate load test; While Poisson's ratio does have some influence on rock deformation modulus, the sensitivity of rock deformation modulus to Poisson's ratio is generally low; When the cohesion of the rock mass is small, the choice of strength criterion has a significant influence on the inversion results of deformation modulus, and vice versa; the sensitivity of the rock deformation modulus to the changes of the rock cohesion varies depending on the depth and lithology of the strata; the deformation modulus of the rock mass obtained by numerical inversion has a good correlation with some empirical equations. Therefore, the numerical simulation and empirical formulae are useful during planning, design and development of deep rock projects to perform the inversion calculation of rock deformation modulus, thereby ensuring greater safety and economy.

The anisotropy in the deformational behavior of blocky rock masses has been comprehensively investigated. The uniaxial deformation modulus was selected as the key parameter. This modulus is generally anisotropic and depends on the loading direction, as well as on the properties of the intact rock, joints, and joint setting. Representative volumes of blocky rock masses were numerically simulated using the discrete element method and were loaded uniaxially in various directions. Subsequently, the failure mode and the deformation modulus were studied for different loading directions and various relative joint settings. A new nonlinear, stress- dependent stiffness matrix for joints was introduced, incorporating the surface conditions of the joints in terms of the Joint Roughness Coefficient (JRC) and the properties of the intact rock materials in terms of the Uniaxial Compressive Strength (UCS). The results of the assessments are presented in the form of rose diagrams, showing variations in the deformation modulus of the blocky rock mass that depend on the joint’s JRC, the intact rock’s UCS, and the structure of the rock mass in term of the relative joint angle. Also, the expected degree of anisotropy for various joint surface conditions and uniaxial compressive strengths of intact rock were introduced. In the Geological Strength Index (GSI) table, results are classified such that assigning a value to the JRC for each class of joint surface conditions allows for the corresponding deformation modulus and degree of anisotropy. According to this chart, it is deduced that the effect of joint roughness on the deformation modulus of blocky rock masses is greater than that of the intact rock UCS. The results support the hypothesis that a blocky rock mass has a critical strain that is independent of the loading angle (θ) and the orientation of the third joint set (α).

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The rock mass deformation modulus is one of the most important design parameters in a range of rock engineering applications. Its value is usually obtained directly through in situ testing or estimated indirectly on the basis of a rock mass quality classification system. Because in situ testing is generally costly, time-consuming, and presents operational difficulties, it cannot be carried out extensively, and many researchers have concentrated on developing indirect procedures to obtain information on the modulus of deformation, such as the RMR method, Q method, and GSI method. The purpose of this paper is to present a new system for estimating the rock mass deformation modulus called the BQ method, which is based on the BQ (basic quality) system. In this paper, the BQ system is first briefly reviewed, and then more than 60 in situ measurements from three large hydropower stations in China are used to develop a new relationship between BQ and the deformation modulus, based on a power function relationship. The paper also derives correlations based on the existing estimation formula and the relationship between BQ and other classification schemes, resulting in several recommended formulas for estimating the deformation modulus of a rock mass using the BQ method. [ABSTRACT FROM AUTHOR]

This study experimentally investigated the variations in pore structure, mechanical property and permeability of concrete under sulfate attack exposed to freeze–thaw cycles, and examined the relationship between pore structure, stress, and permeability. The results indicate that before 10 cycles, the original pores in the specimen are filled with the reaction products of sulfate and concrete matrix. Compared with the specimen at 0 cycles, it is denser with a reduction in T2 area, an increase in peak stress, and a decrease in initial permeability. With the increase in the number of cycles, the accumulation and expansion of ettringite and gypsum in the product lead to the subsequent enlargement of pores, more liquid enters the interior of the specimen, and the frost heave effect caused by the freeze–thaw dominates. Therefore, the mesopores and macropores in the specimen are developed, the fractal dimension is reduced, and the T2 area is increased. Macroscopically, the peak stress decreases and the initial permeability increases. Besides, the existence of hydraulic pressure weakens the mechanical properties (peak stress and deformation modulus) of the specimen, increases the lateral deformation and improves the permeability. [ABSTRACT FROM AUTHOR]

The pressuremeter test (PMT) and plate load test (PLT) are principal in-situ experiments for measuring soil stiffness and deformation parameters. Although the PLT can be costly and complicated at great depths the PMT can be easily done in a borehole. Empirical equations linking the parameters from these tests can be useful for cross-checking the parameters obtained by the two methods and can reduce costs. In the present study, PMTs and PLTs were carried out on fine-grained soil from two sites in Iran. The pressuremeter modulus (EPMT) and limit pressure (PL) from the PMT and plate load modulus (EPLT), subgrade reaction modulus (K) and reload modulus (Er) from the PLT were determined and the relationships between them were investigated. A reliable and significant statistical model for these empirical equations has been was proposed. It was found that the average EPMT was about 25% higher than that of the EPLT and an exponential relationship could be determined linking the parameters at each site. A logarithmic relationship has been proposed between Er and EPLT. The mean absolute percentage error (MAPE) for calculation of the EPLT, K and Er for both sites was less than 15.14, indicating that the proposed equations estimated their values with good accuracy. Comparison of data from PLTs and PMTs in another area recorded a MAPE of less than 13.08. [ABSTRACT FROM AUTHOR]

Deformation modulus is one of the geomechanical parameters of rock masses; it is widely used in the design and numerical modeling of rock structures. This parameter can be calculated using empirical methods and in situ tests. Considering that the results of in situ tests are more reliable than those obtained by the other methods, the plate Jacking test (PJT) is more widely used than other in situ methods, because it affects a larger volume of rock. Investigations demonstrate that the difference between the actual conditions of the PJT and the assumptions governing the theoretical relationship suggested by the International Society of Rock Mechanics (ISRM) causes some errors in the obtained results, and the interpretation of the results is always complicated. In this study, by performing six PJTs in the Azad pump storage power plant (PSPP) project, in the west of Iran, two parallel and two perpendicular to the bedding were selected and the deformation modulus was calculated by using the proposed ISRM equation. The effect of changes on normal and shear stiffness, discontinuity spacing, and the number of discontinuities was investigated through numerical modeling of these tests using the 3DEC software (version 5.20). Subsequently, the results were compared with those of in situ tests and the model that best matched the in situ results was presented. In the first step, the appropriate depth according to the depth of the implementation of the in situ tests was chosen to calculate the deformation modulus parallel and perpendicular to the discontinuity using the numerical modeling. In the second step, the equivalent deformation modulus was estimated based on the analytical formulas and compared with the numerical and experimental results. Furthermore, the influence of various parameters such as the ratio of the dimension of the gallery (W) to the dimension of the loading plate (a), overburden (in situ stresses), and stress ratio (K0) was considered and sensitivity analysis was performed. The results revealed that when the W/a ratio was greater than 10, the gallery dimension effect disappeared. Increasing the K0 ratio and maximum horizontal stress at a constant depth increased the stiffness of discontinuities and decreased displacement, leading to an increased modulus of deformation for the rock mass. The results also showed that, for this site, with increasing depth, the value of the modulus of deformation changed in the range of 12–26 GPa. In addition, the variation in the discontinuity angle showed that the maximum value of the modulus in the state parallel to the bedding (0°) was around 24.3 GPa and the minimum modulus at the angle of 45° was equal to 10.4 GPa, which was in agreement with the in situ test results. Finally, by analyzing the experimental and numerical results, a correction factor was provided to verify the in situ results calculated from the ISRM relation at different depths of the borehole. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Protective seam mining is the most economical and effective measure for eliminating coal and gas herniation. To study the unloading effect of the mining of a protective seam on the protected layer, and to better grasp the effect of the protective layer on the abatement, conventional triaxial tests were conducted on coal samples with the unloading of the axial pressure and the peripheral pressure. The results showed that, under the unloading path, the bias stress–axial strain curve showed a sudden upward trend upon unloading, and the slope of the curve increased suddenly, which was more obvious after the peripheral pressure exceeded 10 MPa; stress unloading before the peak accelerated the yielding of the specimen. Under the unloading test path, the deformation modulus of the coal samples decreased with the decrease in the perimeter pressure, while the damage factor and Poisson's ratio increased with the decrease in the perimeter pressure. Compared to the conventional triaxial test, under the unloading condition, the cohesion of the coal samples at peak stress decreased by 93.41% and the angle of internal friction increased by 37.41%, while the cohesion at the moment of residual strength decreased by 89.60% and the angle of internal friction increased by 37.44°. The brittleness index of the coal samples under unloading conditions with a peripheral pressure of 5 MPa, 10 MPa, 15 MPa, and 20 MPa increased by 178.83%, 159.18%, 87.93%, and 63.89%, respectively, compared to the conventional triaxial test. It can be seen that the greater the enclosing pressure, the smaller the difference in the brittleness index of the coal body. [ABSTRACT FROM AUTHOR]

The evaluation of deformation and strength parameters of Holocene organic soils obtained from DMT dilatometer tests based on empirical relationships and ANN Artificial Neural Networks is presented. The evaluation of undrained shear strength τfu, deformation modulus E0.1% and initial shear modulus G0 of Eemian organic soils obtained from DMT dilatometer tests and SDMT seismic dilatometer tests is given, and then its comparison with the values obtained from triaxial tests for the design of underground structures supported by diaphragm walls of the stations of the underground line II in Warsaw, is shown. [ABSTRACT FROM AUTHOR]

The performance and bearing capacity of the flexible pavement structure is ensured by providing necessary foundation comprised of unbound granular material (UGM) layers and subgrade. Whin this paper the compaction level parameters and deformation modulus relations determined for UGM layers and subgrade in construction site. The experimental data were tested applied standardized and improved test methods, such as an alternative falling weight deflectometer (FWD) test method with repetitive load, the plate load tester, lightweight deflectometer, dynamic cone penetrometer, and density Proctor tests. The data were analyzed based on statistical comparison of the compaction parameters, pairwise multiple comparison of test methods, clustering procedure for setting a level of compaction evidence and variance determination. Results proved capabilities of the alternative FWD test method under repetitive load to assess the relative compactness rate and the resilient responses, and provided the regression models of the dynamic modulus of the UGM layers and subgrade. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To investigate the influence of loading–unloading paths as well as loading and unloading rates on the deformation and failure behavior of coal, laboratory experiments and numerical simulations of unloading under axial pressure and confinement were carried out. The effect of different axial loading rates and unloading rates on the deformation and failure behavior of coal under the unloading path was studied. A damage variable formula was derived based on the variation of the deformation modulus with axial strain, and the evolution characteristics of damage in experimental and numerical simulation results were compared and discussed. The results reveal significant influences of stress path and loading/unloading rates on the deformation and failure behavior of coal. In terms of the influence of loading/unloading rates, the sequence of the ease of coal failure and the speed of damage development is as follows: high unloading rate, low unloading rate, low loading rate, and high loading rate. Compared to the loading rate under axial pressure, the unloading rate under confinement has a greater impact on the deformation modulus and deformation failure of coal, especially within the range of 0.01~0.04 MPa/s. Higher loading and unloading rates can shorten the time for coal failure and accelerate the speed of coal failure. Within the same unloading step interval, the increase in plastic strain under loading rates is generally lower than that under unloading rates. These findings have practical implications for the prevention of disasters. [ABSTRACT FROM AUTHOR]

The rock mass deformation modulus is one of the most important design parameters in a range of rock engineering applications. Its value is usually obtained directly through in situ testing or estimated indirectly on the basis of a rock mass quality classification system. Because in situ testing is generally costly, time-consuming, and presents operational difficulties, it cannot be carried out extensively, and many researchers have concentrated on developing indirect procedures to obtain information on the modulus of deformation, such as the RMR method, Q method, and GSI method. The purpose of this paper is to present a new system for estimating the rock mass deformation modulus called the BQ method, which is based on the BQ (basic quality) system. In this paper, the BQ system is first briefly reviewed, and then more than 60 in situ measurements from three large hydropower stations in China are used to develop a new relationship between BQ and the deformation modulus, based on a power function relationship. The paper also derives correlations based on the existing estimation formula and the relationship between BQ and other classification schemes, resulting in several recommended formulas for estimating the deformation modulus of a rock mass using the BQ method.

The evaluation of deformation and strength parameters of Holocene organic soils obtained from DMT dilatometer tests based on empirical relationships and ANN Artificial Neural Networks is presented. The evaluation of undrained shear strength τfu, deformation modulus E0.1% and initial shear modulus G0 of Eemian organic soils obtained from DMT dilatometer tests and SDMT seismic dilatometer tests is given, and then its comparison with the values obtained from triaxial tests for the design of underground structures supported by diaphragm walls of the stations of the underground line II in Warsaw, is shown.

In order to improve the effect of dry filling of waste rock and improve the filling strength, this paper studies the compaction mechanical characteristics and influencing factors of dry filling of waste rock utilizing physical tests and theoretical calculations. The results show that the particle size gradation of the sample and the continuity of the gradation have a great influence on the compactness of the sample. The compactness of the continuous gradation is lower and the compressive strength of the sample is stronger. Through range analysis, the influence of gradation coefficient n on axial strain is greater than that of maximum particle size D: the axial strain stress curve of the specimen shows that the main source of the macroscopic deformation of the specimen is the direct compression and filling of the pores. The deformation modulus axial stress curve shows that the particle size distribution of the waste rock sample is perfect, and there should be a reasonable proportional relationship between the particle sizes in each range so that the sample reaches a stable state through less axial strain. The fractal characteristics of the sample show that the reasonable Taibo coefficient n and the maximum particle size D can improve the crushing degree of the waste rock particles and improve the compressive strength of the sample. The optimum particle size gradation of waste rock was determined: n = 0. 4,D = 30 mm. The research results have a certain guiding significance for the dry filling of waste rock. [ABSTRACT FROM AUTHOR]

Compressibility of strong and structurally disturbed rocks is determined for predicting land subsidence and stability during operation of transport machines. The plate-bearing tests are carried out on a large bench tester at different normal pressures and different densities of strong overburden rocks. The method to estimate deformability of strong overburden rocks using a plate and a station rod is described. The results were used to assess passability of transport machines during damming, and for the damp stability calculation. [ABSTRACT FROM AUTHOR]

To study the characteristics of lateral unloading deformation of undisturbed loess, the representative Q3 undisturbed loess with different moisture content in Shaanxi Province was selected to carry out graded lateral unloading tests under different consolidation pressures. The results show that the stress-strain curve of undisturbed loess under lateral unloading is hardening. The samples with low initial consolidation pressure had no obvious performance of damage and the axial strain finally tended to be stable, while the samples with high consolidation pressure have damage and the axial strain continued to increase. For the samples with low consolidation pressure, the higher the moisture content, the greater the axial strain at the time of final stability. The critical axial strain ratio of undisturbed loess was put forward, and the exponential function was obtained by fitting, so as to calculate the confining pressure when the soil reaches plastic failure. According to the experimental results, the empirical formula of the initial tangent modulus was obtained, and the formula of the deformation modulus of the undisturbed loess with different moisture content under unloading was derived. [ABSTRACT FROM AUTHOR]

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The tangent modulus method of undisturbed soil is a new method in settlement calculation, which is mainly applied to hard soil with a strong structure, such as silty clay, completely weathered rock, and granite residual soil with an SPT blow count greater than 8. The tangent modulus is mainly obtained from a field plate load test, which can consider the influence of the soil stress level and reflect the nonlinear characteristics of the foundation settlement. In a multi-layer soil foundation, since the deep plate loading test is difficult, a method was proposed to determine the tangent modulus of deep soil. It is assumed that the ratio of the initial tangent modulus to the deformation modulus is equal to the ratio of the unloading–reloading modulus E ur ref to the secant modulus E 50 ref obtained by triaxial unloading–reloading test. Since there are corresponding empirical formulae for SPT counts and the deformation modulus of different types of soils in many regions, the initial tangent modulus can be derived by the above method. In two cases of a composite foundation, the compression modulus and tangent modulus were used to calculate the settlement of the foundation, which is then compared with the measured results. The results show that the proposed method for determining the tangent modulus of deep soil is feasible in theory, and the calculating accuracy of the tangent modulus is significantly higher than that of the traditional compression modulus. [ABSTRACT FROM AUTHOR]

The development of reinforcements for soil has made an impact in most of the civil engineering sectors especially transportation. The use of geogrids is frequent in roadways but they are also finding use in railways. The major impact that geogrids could have is providing desired stiffness to a section by reducing material and serving as a proper reinforcement material. In the current study, an attempt has been made to redesign the railway embankment economically with the help of geogrids. Biaxial geogrid is used to substitute the blanket layer (thickness up to 100 cm) in the railway embankment by fulfilling the strain modulus requirement of the embankment, calculated using a plate bearing test as per DIN 18134. The experiment is performed on the embankment replicated in a metallic test chamber with granular soil as subgrade and geogrid is placed beneath the ballast. The experimental study is validated by a 3-D numerical model using Midas GTS NX software. The experimental analysis shows an improvement of 31.47% in the second modulus of the earth embankment. For the implementation of this study, a design section of Indian railways is adopted. With the help of geogrid, a reduction of 50% is observed in the embankment height, thereby reducing the overall costs.

The use of cement and fly ash (FA) to prepare cemented tailings backfill (CTB) lowers backfill mining costs while also reducing pollution caused by the accumulation of waste materials like tailings and FA, making it a green backfill mining process. While adding FA to CTB may reduce costs, too much FA might weaken CTB's strength property. Mechanical tests were used to explore the effects of FA content and curing time on the uniaxial compressive strength (UCS) and deformation modulus of CTB in this research. The effects of FA content on failure modes, strain energy, and crack evolution of CTB were studied using a numerical model that considered FA content and particle contact mode. The influence mechanism of different FA contents on CTB was also revealed at the microscopic level. The results demonstrate that the UCS of CTB has a quadratic polynomial and a linear relationship with FA content and curing time respectively, and that the elasticity modulus and secant modulus of CTB increase and then decrease with FA content under different curing times. The peak strain energy of CTB increases and subsequently declines with the FA content, and crack propagation inside CTB may be limited by regulating the FA content. A reasonable content of FA can optimize the size and distribution of CTB microscopic defects, enabling them to exhibit superior strength property. This study systematically explores the mechanism of different FA contents on the strength property of CTB from a macro–micro perspective, providing an essential reference value for improving the recycling of FA and waste residues such as tailings. [ABSTRACT FROM AUTHOR]

The effect of overburden stress on the rock mass deformation modulus is a known issue. However, the effect of overburden stress has been studied less with empirical methods due to the lack of appropriate data. In this study, it is aimed to investigate the effect of overburden stress on rock mass deformation modulus using artificial neural network (ANN). Four ANN models have been developed in accordance with the purpose of the study. Two of these models do not contain the overburden stress parameter, but the other two models contain the overburden stress parameter. The prediction performance of the models containing the overburden stress parameter was obtained drastically higher than the others. In other words, the value account for (VAF) and root-mean-square error (RMSE) indices of the model having the inputs of rock mass rating (RMR) and elasticity modulus of intact rock (Ei) are 73.3% and 462, respectively, while those of the model having the inputs of RMR, Ei and overburden stress are 90% and 265. The other models developed in the present study yielded similar results. Consequently, with the ANN models developed in this study, the effect of overburden stress on Em is revealed, clearly. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The deformation modulus of rock mass is an essential parameter for evaluating the bearing capacity and deformations. A deformation modulus obtained through conventional approaches, including empirical equations and in situ tests, cannot present the deformation modulus at representative elementary volume (D REV) due to limited test coverage and technical difficulties in harsh geological or topographic conditions. This study utilized electrical resistivity (ER) tomography and numerical back-analysis to investigate D REV at the Asmari-Jahrum formation. We employed geoelectrical contrasts to detect proper locations for installing extensometers at excavated galleries. The deformations recorded by extensometer were used to back-calculate the D REV values by finite difference numerical modeling. We established a correlation between ER and D REV to predict D REV , which were 30–80 % more accurate than those obtained through conventional approaches at the study site. The tested area, anisotropy, creep, ER inaccuracies, and plastic deformations are evaluated as statistically significant factors that can influence D REV. Our methodology provides a systematical approach to assess D REV , which applies to geoengineering projects within the Asmari-Jahrum formation or similar sedimentary units (ER below 200 Ω⸱m). This methodology is also replicable for other geological formations with harsh geology or limited access without exposing an extreme financial burden or environmental issues. [ABSTRACT FROM AUTHOR]

Introduction. The purpose of the article is a comparative analysis of methods for calculating stamp modules of soil deformation regulated by various standards of the Russian Federation.Materials and methods. The experimental determination of the deformation modules for the soil of the roadbed was performed using stamp tests. The tests were carried out in a soil tray by loading and unloading a soil base compacted to the required compaction coefficient of 0.98. The load was applied by steps, and the stamp draft was measured after completion of deformation stabilization from each step. The criterion for stabilizing the deformation was a decrease in the speed to 0.02 mm / min and the time of application of the load, which should be at least 120 s. After measuring the elasto-plastic draft of the soil, the model was unloaded. Unloading is also carried out by steps. As a result, the dependences of the elasto-plastic and elastic draft of the soil model of the roadbed from the pressure in the form of hysteresis loops are constructed.Results. The calculations of the soil deformation modulus were performed according to the various methods regulated by the standards of the Russian Federation. The calculation results are grouped into data samples that are processed by mathematical statistics methods. When processing data, each sample is checked for the presence of gross errors. The data samples are checked for belonging to one general population. To check whether three samples belong to one general population, the Kruskal W. H. and Wallis W. A. criterion was applied. Based on this comparison, we made judgments about the significance of differences in the samples.Discussion and conclusions. To determine the deformation modulus of soil and road pavements made of granular materials, a method for calculating the modulus of deformation using a method that assumes a nonlinear dependence of deformations on pressures, described by a second-degree polynomial is recommended.

The deformation modulus of a rock mass is an important parameter to describe its mechanical behavior. In this study, an analytical method is developed to determine the deformation modulus of jointed rock masses, which considers the mechanical properties of intact rocks and joints based on the superposition principle. Due to incorporating the variations in the orientations and sizes of joint sets, the proposed method is applicable to the rock mass with persistent and parallel joints as well as that with non-persistent and nonparallel joints. In addition, an anisotropy index AIdm for the deformation modulus is defined to quantitatively describe the anisotropy of rock masses. The range of AIdm is from 0 to 1, and the more anisotropic the rock mass is, the larger the value of AIdm will be. To evaluate the proposed method, 20 groups of numerical experiments are conducted with the universal distinct element code (UDEC). For each experimental group, the deformation modulus in 24 directions are obtained by UDEC (numerical value) and the proposed method (predicted value), and then the mean error rates are calculated. Note that the mean error rate is the mean value of the error rates of the deformation modulus in 24 directions, where for each direction, the error rate is equal to the ratio of numerical value minus predicted value to the numerical value. The results show that (i) for different experimental groups, the mean error rates vary between 5.06% and 22.03%; (ii) the error rates for the discrete fracture networks (DFNs) with two sets of joints are at the same level as those with one set of joints; and (iii) therefore, the proposed method for estimating the deformation modulus of jointed rock masses is valid.

Copyright of Fly Ash Comprehensive Utilization is the property of Hebei Fly Ash Comprehensive Utilization Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Zhanjiang Formation gray clay has physical properties similar to the muddy clay of other areas, such as a large void ratio and high-water content. At the same time, it also has mechanical properties that differ from muddy clay in other areas, such as high strength and low compressibility. When calculating the foundation settlement, the equation that calculates the foundation settlement as suggested by the code tends to produce values of compression modulus that are too small, which leads to larger calculated values. This study investigated the relationship between the pressure and deformation of Zhanjiang Formation gray clay foundations with different densities, water content, and stress histories by means of a plate loading model test. It revealed the influence of these factors on the deformation modulus, and the quantitative relationship between this modulus and the density of soils, water content, and the over consolidation ratio was established. In doing so, the aforementioned quantitative relationship was applied to the equation which calculated the foundation settlement as suggested by the current code, thereby proposing a pertinent formula relevant to Zhanjiang Formation gray clay foundations. The formula was subsequently applied to two engineering examples, and the settlement amounts output were in agreement with actual measured values, indicating it is reasonable and feasible for practical application. Therefore, it can provide a reference for the calculation of foundation settlements across the coastal area of Beibu Gulf. [ABSTRACT FROM AUTHOR]

Machine learning-based methods have recently found an extensive field especially in engineering applications. In this study, net limit pressure (PLN) and deformation modulus (E) were tried to predict using the data obtained from in-situ and laboratory tests which were performed for cohesive soils. For this purpose, three different machine learning methods were employed such as regression trees (RT), support vector machines (SVM), gaussian process regression (GPR). The corrected SPT (SPT-N(60)), liquid limit (LL%), plasticity index (PI%) and unit weight data are the input parameters of the models. Three machine learning methods were utilized for each constructed model. Accordingly, SVM and GPR methods have higher prediction performance than RA. When the models are compared which were constructed for the prediction of PLN and E; the prediction performance of PLN is higher. Consequently, it has been concluded that three different machine learning methods can be used to predict PLN and E, and their representativeness is high, especially in the cases where field studies are costly and difficulties of sampling. [ABSTRACT FROM AUTHOR]

With the continuous improvement of the construction of the ecological economic system in the new era, the problem of heavy metal pollution has become an important issue in urban construction. In this paper, Zn2+ contaminated red clay is used as the research object, and calcium superphosphate and calcium oxide are used as curing agents to conduct the simultaneous test of unconfined compressive strength-resistivity. The mechanical properties and resistivity of the contaminated soil under different test conditions were analyzed to investigate their effects on the cured red clay. The results showed that different contamination concentrations showed different weakening effects on the unconfined compressive strength of red clay soils, and the unconfined compressive strength of cured soils increased significantly. The age of maintenance affects the unconfined compressive strength of cured soil, and the growth of unconfined compressive strength is most obvious in the age of 0–7 day. After that, it tends to be stable with the growth of age. The deformation modulus of contaminated soil before and after curing was reduced to different degrees. Before and after curing, the resistivity of contaminated soil decreased with the increase of ion concentration, and the resistivity of cured soil increased with the increase of curing agent incorporation rate under the same contamination concentration. The research results can enrich the soil treatment problem of heavy metal contaminated sites and provide theoretical support for the application of this type of curing agent in the field engineering of Zn2+ contaminated red clay soil. [ABSTRACT FROM AUTHOR]

Several rock mass properties need to be determined for engineering project execution; among them, rock mass quality and the deformation modulus have a vital importance for the design and successful execution of rock engineering projects. Estimation of deformation modulus of rock mass is done by in situ measurement as well as existing empirical relationship derived from various rock mass classification system. In situ tests are more time-consuming, more expensive, and have operation difficulties. In contrast, estimation of deformation modulus by rock mass classification system is very simple, less time-consuming, and economical but due to a large number of existing empirical equations, the question arises to which empirical relationship provides the most reliable estimation of the deformation modulus. This paper will review and compare the performance of existing empirical equations derived from rock mass classification system, RMR, Q, and GSI on Nepal Himalayan terrain. For the purpose of the study, the data obtained from Headrace tunnel of upper Chaku A hydroelectric project was used. The RMR, Q, and GSI values were calculated along the headrace tunnel for the assessment of rock mass. The values of Em were calculated using the existing empirical equations based on the RMR, Q, and GSI. The estimated values of Em by various equations are compared with respect to variation trend of rock mass quality of study area. The relationships between Em and RMR, Em and Q, and Em and GSI were obtained via simple regression analysis using geometric average Em. The proposed equations were validated from the field investigation results of deformation modulus. [ABSTRACT FROM AUTHOR]

In this study, waste concrete fine aggregates and cement are applied to sludge solidification and resource recycling. The unconfined compressive strength (UCS) test is performed to investigate the variation in the strength and stress–strain properties of the solidified sludge with the content and particle size of waste concrete fine aggregate, cement content, and curing time. The results show that incorporating waste concrete fine aggregates can improve the UCS of cement-solidified sludge, which can achieve the optimum effect when the fine aggregate content ranges from 12% to 15%. However, compared with the fine aggregate content, the cement content and curing time are the main factors in improving the strength of waste concrete fine aggregate and cement-solidified sludge (WCSS). The stress–strain curves of WCSS comprise four stages. The failure strain εf of WCSS with four fine aggregate contents decreases in a power function with the increase in qu, and εf is mostly distributed when the content is 1.1–2.1%. A linear relationship is observed between E50 and qu. This study attempts to promote the recycling of waste concrete fine aggregates and obtain solidified sludge with excellent mechanical properties, providing some reference for practical engineering applications. [ABSTRACT FROM AUTHOR]