Values Of Deformation Modulus Research Articles

Examining intermediate soil properties variability through spatial interpolation methods in GIS

This study compares Kriging and Inverse Distance Weighting (IDW) spatial interpolation methods for estimating intermediate soil properties at a construction site in Astana, Kazakhstan. Using data from eight boreholes, seven engineering geological elements (EGE) were identified and analyzed at 6.5 m and 11.5 m depths. Kriging produced deformation modulus values ranging from -0.29 to 18.99 MPa at 6.5 m and -0.51 to 23.94 MPa at 11.5 m, capturing more spatial variability compared to IDW, which provided ranges of 3.3 to 18.99 MPa and 2.6 to 23.99 MPa, respectively. Kriging’s ability to account for spatial correlations resulted in more accurate predictions, particularly in areas with complex subsurface variability. Meanwhile, IDW offered reliable localized results, effective in more uniform geological conditions. The findings demonstrate that both methods are valuable for geotechnical applications, with the choice depending on data density and site variability.

Toward the use of an intermediate value of the modulus of deformation of soils in geotechnical design

This study presents the results of a critical analysis of the existing methods of selecting the values of ground deformation modulus used in calculating the settlement of designed foundations. The importance of improving the reliability of the determination of the modulus of deformation for ensuring the reliability, economic efficiency and safety of structures is highlighted. It is revealed that the determination of the deformation modulus is not performed at the full depth of soil samples, which can lead to the risk of accidents at facilities. To increase the reliability of deformation modulus determination, a method of interpolation of values based on data from nearby wells is proposed. A new model for determining intermediate values of the deformation modulus is presented, which can be used in calculating the settlement of designed buildings. The results of test problems confirm the high efficiency of the proposed method not only for the calculation of foundation settlement using the values of ground deformation modulus, but also for the control determination of refined values of ground deformation modulus at the stage of geotechnical engineering surveys.

SUBSTANTIATION OF THE ROAD CONSTRUCTION UNBOUND MATERIALS CALCULATION MODEL WITH GEOGRIDS STABILIZATION

Summary. Based on the results of experimental studies conducted on different types of flexible pavement structures, the authors of the article examined the behavior of unbound material reinforced with geogrid. A series of static plate load tests were carried out, and the deformation modulus values of traditional and reinforced pavement structures were determined. The impact of the geogrid, installed at the base of the unbound layer of the pavement structure, on its deformation modulus was investigated. It was found that the use of geogrids significantly increases the equivalent deformation modulus of the pavement, depending on the thickness of the inert material layer and the deformation characteristics of the subgrade soil. The effectiveness of the reinforcement depends on the ratio of the deformation characteristics of the pavement and the subgrade soil, as well as the relative depth of the geogrid installation. The greatest effect is achieved on weak soils under large deformations. The results obtained are significant for further research and practical application of pavement reinforcement technology using geosynthetic materials. Keywords: highway, pavement structure, biaxially oriented geogrid, geosynthetic reinforcement, plate load tests, deformation characteristics, loading, reinforcement coefficient, field experiment

Inverse analysis of deformation moduli for high arch dams using the displacement reconstruction technique and multi‐objective optimization

AbstractThe inverse analysis of the deformation moduli of high arch dams based on displacement monitoring data is essential for structural safety assessment. In traditional inverse analysis methods, the deformation moduli are identified based on the single‐objective optimization and the hydrostatic component derived from the statistical model. This type of method has two main shortcomings: First, it treats the essential multi‐objective optimization problem as a single‐objective problem; second, the extracted hydrostatic component may be biased due to the multicollinearity of variables in the statistical model. This paper presents a methodology for the inverse analysis of the deformation moduli of high arch dams under a multi‐objective optimization strategy. The methodology employs empirical mode decomposition to extract the aging component from displacement monitoring data. Then, thermomechanical analysis is used to reconstruct the remaining hydrostatic and temperature components, thereby avoiding the biases encountered in solving the statistical model. The adaptive polynomial chaos expansion method is embedded in the NSGA‐III algorithm to establish and solve multi‐objective functions in the inverse analysis. Additionally, a composite decision index considering errors and test information is proposed to determine acceptable deformation moduli from the Pareto solution set. A high arch dam is selected to illustrate this methodology with static and dynamic monitoring data. The results show that the identified deformation moduli have errors of 3.8% and 7.2% in displacement and acceleration, respectively. The proposed methodology can yield deformation modulus values that are more consistent with the physical implications than those of the single‐objective optimization method.

Geotechnical and Geophysical Investigations of Estimating Rock Mass Properties

Accurate assessments of the deformation and strength properties of rock masses are essential for analysing the foundations, subsurface excavation, and construction of slopes, however, identifying geotechnical properties, particularly weak rock masses, is challenging for geoscientists, geologists, and geotechnical investigators. To determine the rock mass properties, geophysical techniques, and rock mass classification methods are widely used. Although rock classification methodologies exist, they are rarely employed in foundation construction analysis due to being predominantly established for tunnelling purposes. This study aims to employ classification methods, and geophysical and geotechnical investigation approaches to provide realistic rock mass properties for a building foundation, compare results, and assess techniques' effectiveness; it also reviews current state-of-the-art methods for classification techniques and investigations. Results show that compressional and shear wave velocities increase with depth indicating a change from poor to satisfactory mechanical behaviour, and empirical equations provide highly valuable and satisfactory deformation modulus values when compared to field seismic values. Almost all classification methods provided reasonable results compared with the seismic results, however highly overestimated and underestimated outcomes were obtained from some empirical equations applying the Rock Quality Designation index and Rock Mass Rating system. Empirical equations that gave the practical deformation modulus outcomes are the Rock Mass Rating based equations and Q-based equations and Geological Strength Index-based equations. Overall, the Rock Quality Designation index underestimated the seismic result, whereas the Rock Mass Rating, Q, and Geological Strength Index systems produced good agreement and realistic results. To conclude, classification methods were effectively applied to a building foundation. Since the Rock Quality Designation is a key value and feature for other systems including Q, and Rock Mass Rating systems, it is an essential factor. Although the Q systems provided practical consequences, this system mainly relied on the Rock Quality Designation value not the compressive strength of the intact rock. The Rock Mass Rating and being the most feasible and essential systems due to detailed geotechnical observations as inputs more significantly the uniaxial compressive strength of the intact rock, and various factors including deformation modulus, strength, Poisson’s ratio, equivalent cohesion, and friction angle of rock mass as outcomes.

Prediction of Primary Deformation Modulus Based on Bearing Capacity: A Case on Forest Road with a Light Falling Weight Deflectometer Zorn ZFG 3000 GPS

Bearing capacity and compaction are among the most important and frequently used geotechnical parameters in road construction. The aim of this study was to determine the possibility of predicting the value of the primary deformation modulus E1 (obtained from measurements using a static plate load test—PLT) based on measurements with a Zorn light falling weight deflectometer (LFWD), type ZFG 3000 GPS, with a drop weight of 10 kg. A regression analysis was performed on 245 bearing capacity measurements that were taken on 46 forest road sections with various road surfaces. Different regression models were tested, from linear to logarithmic, polynomial, exponential and power models, but excluding polynomials of fourth and higher degree. The results showed that the prediction of E1 values (PLT) from the dynamic deformation modulus values Evd (LFWD) was possible. However, the reported unsatisfactory strength of the relationship between the two parameters was associated with a high risk of error (r = 0.64, R2 = 0.41, Se = 49.78). Neither the use of more complex non-linear regression models, nor the use of multiple regression by introducing an additional estimator in the form of the s/v ratio, significantly improved estimation results. The quality of the prediction of the E1 value was not constant. It varied, depending on the type of forest road, the use of geosynthetic reinforcement and the type of road subgrade. During the study, it was also found that the quality of the prediction of the E1 value could be improved by limiting the range of Evd values tested from above. It is advisable to continue this type of research, as the obtained results could form the basis for future development of national standards for the use of LFWDs to control the bearing capacity and compaction of forest road pavements.

STRENGTH AND STABILITY ASSESSMENT OF NPP REINFORCED CONCRETE STRUCTURES REGARDING THE RESULTS OF VIBRATION ANALYSIS

Introduction . The article outlines methodological stages when assessing the resource of nuclear power plant (NPP) operation units with regard to degradation in the dynamic characteristics of reinforced concrete structures obtained by means of vibration analysis methods on the example of hot cells of nuclear installations. Aim : to improve the method currently used for assessing the stress-stain behavior and strength of NPP structures regarding the aging process of reinforced concrete elements under various environmental exposures. Materials and methods . A methodology is proposed for assessing the strength (loading capacity) and stability of NPP structures where significant variations in the properties of reinforced concrete elements have taken place under the action of continuous operation and thermal mode disturbances, thus weakening the element stiffness and, as a result, reducing their strength and stability. Therefore, in order to evaluate the stress-stain behavior and strength of hot cells, calculations should be carried out taking into account the history of structure loading and the process of crack development over the entire operation period. However, no analysis of the history of thermal loading has been performed during the operation period of the NPP under study. In addition, there is a lack of suitable software packages for nonlinear dynamic analysis certified by Rostechnadzor capable of considering the loading history and crack development in reinforced concrete structures. In order to eliminate the mentioned shortcomings, a vibration analysis of the walls and floors of hot cells should be performed to determine the following dynamic characteristics: natural vibration frequency and mode, logarithmic decrement of damping, deformation modulus and Poisson ratio for each wall and floor. Further, based on the obtained experimental data, the stress-stain behavior and strength of hot cells should be calculated using experimental data as calculation input information. The calculation methodology is based on a nonclassical method of modal superposition using the ABAQUS, ANSYS, and Nastran software packages. In order to verify the correctness of the results obtained by vibration analysis, an assessment of floor dynamic characteristics at the point +13.450 in the “П”–“Ж” rows was conducted. Results . The values of deformation modulus and natural vibration frequency obtained in the conducted experiment were found to agree with the calculated values. Conclusions . A methodology for assessing the strength of NPP structures regarding the aging of reinforced concrete under various environmental exposures was presented. The validity of dynamic characteristics obtained using vibration analysis was evaluated.

Estimation of rock mass deformability based on empirical relations for Ghezel Ozan dam site in the north of Iran

Rock mass deformability modulus is one of the most important parameters for underground structures and dam site design. The current methods for determining this parameter are in situ tests and empirical equations. In situ tests are the best and most accurate methods and include plate bearing, flat jack and dilatometer tests. However, these in situ tests are difficult, time-consuming, expensive and sometimes even impossible. Therefore, many empirical equations have been developed to determine the rock mass deformability indirectly based on various parameters. In this study, the correlation between the deformation modulus values, rock mass rating (RMR) and tunnelling quality index ( Q ) classification has been studied for the Ghezel Ozan dam site in NW Iran. Then, empirical equations are used to calculate the rock mass deformation modulus ( E m ) based on dilatometer in situ tests and rock mass classifications as mentioned above are defined. Finally, the correlation between the equations given in this study and the empirical equations presented by other researchers based on RMR and TQI ( Q ) are also investigated using statistical indicators. According to this analysis, the equation estimated based on RMR has a good compliance with the equations presented by earlier researchers. Supplementary material: Supplementary datasets and figures are available at https://doi.org/10.6084/m9.figshare.c.6139108

Rock burst forecasting technique and selecting a safe coal face advance direction

Mine planning involves selecting an optimal mine layout. At the same time key factors, including those influencing mining safety, should be comprehensively taken into account. A developed rock burst forecasting technique taking into account mine workings of an extraction area and a mine goaf enables determining the safe direction of a coal face. The proposed technique also takes into account all faulting/joint systems, occurring beyond a mine field. The distribution of specific potential energy in an intact rock mass is proposed to be used as the basis of the input data required for rock burst forecasting. The forecast is carried out via estimating the Lode-Nadai coefficient at different directions of coal face advancing. The stress (intensity) coefficient is proposed to be used as a criterion in order to determine a safe direction. We determined the safety criterion is equal to 10 in the Komsomolskaya Mine conditions. Besides, the safest direction of a coal face advance to mitigate the risks of rock burst was determined for this mine. The direction between 138° and 128° counter-clockwise from the north direction was identified to be the safest for the Komsomolskaya Mine conditions for any values of deformation modulus and Poisson’s ratio.

Deformation modulus of rock foundation in Deriner Arch Dam

Civil engineering structures such as gravity concrete dams, arch dams, pressure tunnels, foundations of high-rise buildings and bridges are generally founded on rock. Design and performance of these structures are highly dependent on the deformation modulus of the rock mass so that expected deformations and/or differential settlements stay within the tolerable limits of the structures. In situ deformation modulus measurements of rock masses are generally performed by using the borehole dilatometer and plate loading tests in Turkey. The diameter of plate loading test device is 30-35 cm. Tests are performed in small unlined tunnels excavated in different elevations of dam abutments. The deformations upon loading are measured on the loading plate in the plate loading tests. It is not possible to exclude the effect of excavation disturbed zone since deformations are not measured with these devices. Large diameter plate test system may have multiple level extensometers set in drill holes opened perpendicular to loading plates. Reading from these extensometers may be utilized to exclude the effect of disturbed zone close to surface together with stress distribution estimated by using elastic theory. There are several field test methods for determining deformation modulus and each method has its own shortcomings. The optimum methodology to correlate plate loading test results with corresponding in-situ deformation modulus values is to back-calculate deformation modulus by using settlements measurements during the construction of dam body. In this paper, Deriner Arch Dam settlements measured during the construction are used to back calculate deformation modulus. It is found that in situ deformation modulus is about two times higher than the average value determined by plate loading tests. This finding will have important effects on the depth of foundation excavations, concrete layers to fortify structure foundations and the amount of consolidation grouting

Engineering properties of plastic waste reinforced sand

A series of triaxial compression tests were performed to evaluate the benefits of plastic wastes and investigate the engineering properties of sand reinforced with these materials. In this research, the effects of plastic waste contents (0, 0.25, 0.5, 0.75, and 1% by dry weight of sand), types of plastic wastes -polyethylene terephthalate (PET) and polypropylene (PP) fibers- and confining pressures (50, 100 and 200 kPa) on the behavior of Babolsar sand were investigated. The values of deformation modulus (up to 84%), peak (up to 7 times of the unreinforced sand) and steady state shear strength increased with reinforcement. Also, axial strain at failure for fiber-reinforced sand increased up to 1.5 times of unreinforced one (from 3.36% to 8.53% for 1% PP usage at 50 kPa confining pressure). Therefore, it can be generally stated that the use of plastic wastes in the sand leads to low cost soil reinforcement and also lessens the disposal problem of these kinds of wastes.

ASSESSMENT OF SOILS DEFORMABILITY UNDER VERTICAL LOAD

Laboratory and experimental tests in huge amount are required during engineering surveys for large and critical buildings and structures especially in complex geological conditions. The laboratory investigations are applicable in cases with no possibility for field tests. However, as a rule the results obtained from laboratory investigations (in particular compression tests) show conservative values of deformation modulus, which leads to underestimate of soil foundations load-carrying capacity, cost increase of foundations for buildings and structures as well as significant overrun of expensive construction materials. The paper shows laboratory tests results (compression and stabilometric) for unixial and triaxial compression of soil samples; results of field plate-load tests for vertical pressed load over natural soil massif. It also brings comparison of stress-strain properties obtained by results of compression, stabilometer and plate-load tests with derivation of regional correction factors for Nur-Sultan City (Kazakhstan). In case of using the recommended regional coefficients while determining the overall deformation modulus by laboratory tests, a significant economic effect is achieved as a result of cost reduction for materials and construction of foundations for buildings and structures.

Interrelations of various soil types mechanical properties

The article aims at assessing relationships of deformation modulus, cohesion and angle of internal friction of various soil types with penetration resistance (cone index). Research methods include analysis of reference information, computational experiment and approximation of calculated data. The analysis is performed for calculated values of mechanical properties of coarse-grained sand, medium-grained sand, fine-grained sand, silty sand, sandy loam, loam and clayey soil. It is found out that angle of internal friction and cohesion of sandy soils, sandy loam, loam and clayey soil are related to deformation moduli by power dependences. Coefficients of the formulae depend on the soil type and, according to the results of calculated data processing, are invariant with respect to porosity coefficients and consistencies of the soils. It is shown that cone indices are related to deformation moduli by power dependences, the coefficients of which are determined by soil type and are invariant with respect to the porosity coefficients and consistencies. The obtained calculated values of the cone indices correspond well with reference data on the penetration resistance of mixed soils. The dependences intend to simplify procedure for estimating mechanical properties of the bearing surface, since, with a soil type known, using the value of deformation modulus or cone index, it becomes possible to calculate the soil parameters characterizing the shear resistance.

Correlations of in situ modulus of deformation with elastic modulus of intact core specimens and RMR values of andesitic rocks: a case study of the İzmir subway line

The main purpose of this paper is to obtain the rock mass rating (RMR) from different methods considering either the elastic modulus of intact rock specimens (Ei) and the modulus of deformation of andesitic rock mass (EM) or only the value of the in situ modulus of deformation, and to compare these values. This paper also presents comparisons between the values of deformation modulus obtained from pressuremeter tests in andesitic rock mass and the values of elastic modulus of intact rock core specimens retrieved from the same boreholes and depths at which pressuremeter tests have been carried out. The pressuremeter tests were conducted on weathered and fractured andesites observed along the Izmir subway route. Correlations between in situ moduli of deformation gathered from 32 pressuremeter test points and calculated RMR values for the andesites at the railway elevation of the Izmir subway were obtained as follows: EMPT = 0.0237 × e (0.0975 × RMR), R2 = 0.848 and RMR = 38.043 × EMPT(0.3291), R2 = 0.77. Finally, the results of comparisons between the modulus of deformation obtained from pressuremeter tests and the geomechanical quality of the rock mass, discontinuity effect, and the basic intact rock properties such as uniaxial compressive strength (UCS) and elastic modulus (Ei) have been discussed. In addition, engineering geological conditions of the andesitic rock masses located at the railway elevation of the Izmir subway were determined in detail.

Deformation Modulus of Rock Masses: An Assessment of the Existing Empirical Equations

Rock mass deformation modulus is an important parameter for all geotechnical applications. However, the determination of rock mass deformation modulus with in situ tests are highly expensive and time consuming. For this reason, rock engineers and engineering geologists have proposed numerous empirical equations based on various rock mass and intact rock properties to estimate the deformation modulus of rock masses. In the present study, an assessment of the existing empirical equations was undertaken. For the purpose of the study, the data obtained from four investigation galleries opened during a dam construction (Artvin Dam, Turkey) were used. A total of 34 plate loading tests were employed in these galleries. The tested rock mass is poor quality tuff. Rock mass rating (RMR89), rock tunnelling quality index (Q) and geological strength index of each test levels were determined. The empirical deformation modulus values of rock mass were calculated by the 26 most cited empirical equations proposed by various researchers. The cross-checks between the measured rock mass deformation modulus and the empirically calculated rock mass modulus values were performed by simple regression analyses. The empirical equations with higher prediction capacity were also examined with root mean square error, values account for and prediction error evaluations. Among the empirical equations compared in this study, two empirical equation giving best performance and other four empirical equations providing acceptable results were determined.

COMPARISON OF THE SOIL DEFORMATION MODULUS VALUES RECEIVED BY THE LABORATORY AND IN SITU TESTS RESULTS

The soil deformation modulus largely depends on the obtaining method. There are various methods of determining E. In compression soil test a ring of small size is used. It causes a number of factors affecting the test results. The comparison of deformation modulus values obtained by in situ and laboratory methods is shown in article. It was believed for a long time that the oedometer deformation modulus of sands practically does not differ from the plate deformation test modulus, and therefore no transitional coefficients for this soil are given. However, it has been experimentally established that the results of oedometer tests of sands need to be corrected.

INFLUENCE OF DEFORMATION MODULI ON THE SETTLEMENT OF EARTH DAMS

The efficiency of compaction of earth dam’s embankment is influenced by the initialcharacteristics of the soils, namely the deformation modulus and density. These two parameters automaticallyaffect the deformations of the dam which can directly impact on its safety. The modeling of thesedeformations is an essential investigation allowing the comprehension of the dam’s behavior. The mainobjective of modeling is to analyze the behavior of the dam and compare it with monitoring data. A lot ofdifficulties are recorded for the estimation of embankments deformation moduli required for modeling. Aparameterized analysis in relation to the variation of this parameter is necessary for the estimation of earthdam’s settlement. The present study concerns the parameterized analysis of the correlation between theparameter influencing compaction, especially deformation modulus, and the deformations of the dam. Anapplication carried out on the Boughrara dam in the region of Tlemcen in the north-west of Algeria ispresented. The modeling result is compared with the monitoring measurements of dam. This study led to theverification of the compatibility, for different values of deformation modulus, between the settlement of thedam by modeling and by monitoring in order to validate the mechanical behavior of the dam.

The influence of loading plate diameter on the results of trial load tests of dynamic replacement columns

The dynamic replacement method of soil strengthening consists in the constructing columns made of aggregate of various granularity. In order to form them, heavy pounders (weighing from 10 to 20 tonnes) are dropped from the height of 25 m. Considering the specificity of this technique, it is quite important to verify on site the assumptions of the project, such as diameter and length of columns, their compaction or stiffness. For that reason, a number of examinations are performed, including column excavations, various types of probing tests or trial loads. The latter consists in determining the “load-settlement” dependence - usually during initial and secondary loadings phase – and on their basis, indicating the value of deformation modulus. Therefore, a stiff plate is placed on the column head and the loading is realised using actuators leaning on the ballast. The diameter of the loading plate depends on diameter and length of column and on the predicted pressure under the plate. The diameter of the loading plate is often smaller than column's diameter. This paper tries to determine the influence of the diameter of the plate used in test loads on the result of the research presented as “load-settlement” dependence and on the values of deformation modulus determined on their basis. The calculations were performed using FEM on a spatial numerical model calibrated on the basis of column's bearing capacity tests. Two models were applied in calculations: elastic-ideally plastic and isotropic hardening elastoplastic.

Determination and applications of rock quality designation (RQD)

Characterization of rock masses and evaluation of their mechanical properties are important and challenging tasks in rock mechanics and rock engineering. Since in many cases rock quality designation (RQD) is the only rock mass classification index available, this paper outlines the key aspects on determination of RQD and evaluates the empirical methods based on RQD for determining the deformation modulus and unconfined compressive strength of rock masses. First, various methods for determining RQD are presented and the effects of different factors on determination of RQD are highlighted. Then, the empirical methods based on RQD for determining the deformation modulus and unconfined compressive strength of rock masses are briefly reviewed. Finally, the empirical methods based on RQD are used to determine the deformation modulus and unconfined compressive strength of rock masses at five different sites including 13 cases, and the results are compared with those obtained by other empirical methods based on rock mass classification indices such as rock mass rating (RMR), Q-system (Q) and geological strength index (GSI). It is shown that the empirical methods based on RQD tend to give deformation modulus values close to the lower bound (conservative) and unconfined compressive strength values in the middle of the corresponding values from different empirical methods based on RMR, Q and GSI. The empirical methods based on RQD provide a convenient way for estimating the mechanical properties of rock masses but, whenever possible, they should be used together with other empirical methods based on RMR, Q and GSI.

Modeling deformation modulus of a stratified sedimentary rock mass using neural network, fuzzy inference and genetic programming

This paper investigates a series of experimental results and numerical simulations employed to estimate the deformation modulus of a stratified rock mass. The deformation modulus of rock mass has a significant importance for some applications in engineering geology and geotechnical projects including foundation, slope, and tunnel designs. Deformation modulus of a rock mass can be determined using large scale in-situ tests. This large scale sophisticated in-situ testing equipments are sometimes difficult to install, plus time consuming to be employed in the field. Therefore, this study aims to estimate indirectly the deformation modulus values via empirical methods such as the neural network, neuro fuzzy and genetic programming approaches. A series of analyses have been developed for correlating various relationships between the deformation modulus of rock mass, rock mass rating, rock quality designation, uniaxial compressive strength, and elasticity modulus of intact rock parameters. The performance capacities of proposed models are assessed and found as quite satisfactory. At the completion of a comparative study on the accuracy of models, in the results, it is seen that overall genetic programming models yielded more precise results than neural network and neuro fuzzy models.