Soil Deformation Modulus Research Articles

Field Evaluation of Deformation Modulus of Geogrid and Geocell-Stabilized Subgrade Soil

Field Evaluation of Deformation Modulus of Geogrid and Geocell-Stabilized Subgrade Soil

Geotechnical issues of investigation of the technical condition of the structure on weak soils according to the boundary element method

The article considers the controversial issue of the need to take into account the increasing coefficient to the soil deformation modulus obtained on the basis of compression studies for the design of loess frozen soils. It is well known that weak soils can have low bearing capacity and high compressibility, which makes them difficult to construct and operate structures. It is known that in laboratory conditions, the modulus of soil deformation is usually determined by compaction with a static load without the possibility of lateral expansion in a rigid ring. The disadvantage of the compression device is the low accuracy of measurements, which is emphasised by many researchers due to the fact that the friction forces of the soil sample on the ring walls reduce, depending on the moisture content and soil type, the vertical pressure applied to the sample during the test. This leads to a false decrease in the actual value of the soil deformation modulus. To determine the reliability of the two approaches to determining the soil deformation modulus, the settlements of the foundations of grain storage silos on dangerous degraded loess soils were calculated by the numerical method of boundary element (MBE) using an elastic-plastic model, with and without taking into account the soil deformation modulus. It has been found that solving the problems of assessing the technical condition of a building is associated with geodetic and engineering-geological surveys and the analysis of these results, since the stress-strain state of the building-foundation system and the peculiarities of deformation of the soil base depend on them. After all, the problem of protecting a building from rolling is quite relevant. The design or reconstruction of structures on foundations with weak soils (with a deformation modulus E < 5 MPa) is also associated with the problem of ensuring that the calculated deformation values do not exceed their maximum permissible values for the experimental structure. The results of numerical studies are compared with the method of finite element (MFE) calculation and experiment.

Dependence of the Dynamic Modulus of Soil Deformation on Impact Frequency

Dependence of the Dynamic Modulus of Soil Deformation on Impact Frequency

Obtaining the empirical calibration dependence for express assessment of the quality of the performance of ground structures

In this study, the authors consider sand pads, namely the production process and quality control. The main problem of using the compacting factor as a criterion for assessing the quality of sand pads is the impossibility of calculating future deformations of foundations, as well as the duration of laboratory studies to determine it. Thus, the development of a technological solution for the use of express methods for controlling the compaction of soil structures, which are based on empirical data and can reduce the economic costs of construction, is an urgent task. The direct object of the study is the sand pad under the production facility. In the process of installing a sand pad, layer-by-layer control of the degree of compaction was carried out according to the compacting factor with the determination of the maximum density according to the method of GOST 22733-2016, and the modulus of soil deformation according to selected soil samples for compression tests. For each layer, the compaction coefficient was determined at 5 points, the deformation modulus at 3 points. Additionally, tests were carried out using a dynamic density meter. The main result of the study is the construction of a calibration dependence of the constrained modulus on the dynamic modulus of elasticity of the soil based on the results of statistical processing. Based on the test results, it was found that the experimental data are equally accurate, the resulting model is adequate. The difference between the experimental data and the calibration dependence does not exceed 18 %, which is a good convergence for empirical methods. The obtained experimental dependence allows, with a sufficient degree of accuracy, to quickly control the quality of the sand pad.

Hazard Curves for Reliability Assessment of Strip Footings on Spatially Varying Cohesive Soils

The present study aimed to create a series of hazard curves against maximum total settlement and angular rotation of strip footings for probabilistic shallow foundation design on clays. Random field finite element method (RFEM) was adopted with elasto-plastic clay-like soil behavior, deformation modulus (Ed) and shear strength parameters (c and ) were employed as random field inputs. Parameters were defined and assigned to the analysis models with varying correlation lengths (h, v). Models have been iteratively solved one thousand times, and output distributions of maximum settlement and angular rotations were recorded. Probability density functions (PDF) were fitted to the outputs, and probability of failure (Pf) for footing deformation limits was subsequently estimated. Proposed hazard curves for two anisotropy and three variability categories were developed employing the estimated Pfs. The method proposed has been validated using an independent database of in-situ results, and a worked example was provided to illustrate the implementation of the process. The key contribution of the research is to form hazard curves for shallow foundations considering elasto-plastic soil behavior with the impact of all influencing parameters, respecting the limit values for foundation deformation in the design codes. The proposed technique offers a probabilistic evaluation of strip footings with spatial variation of clayey soils and a valid method for the reliability-based design of foundations in the serviceability limit state.

Determining the Stabilised Subfoudation Soil Deformation Modulus According to the Plate Load Tests and Geotechnical Monitoring Data

Introduction. The subsiding soils, which are widely spread in the south of Russia, create a number of problems and hazards due to the high probability of subfoundations subsidence in case of exceeding the values of initial soil moisture and initial pressure for subsidence. This is an important phenomenon to be considered at all life cycle stages of a building or structure, especially at the stage of design, when the scientifically justified design and technological solutions must be developed to ensure the reliable operation of facilities in the complicated engineering and geological conditions being studied hereby. The present article analyses the acting federal and regional regulatory and technical documentation in the field of buildings and structures design on the subsiding soils. Based on the numerical experiment, the incorrectness of the results sometimes received upon following the normative methodology is shown. A new calculating methodology based on determining the stabilised subfoudation soil deformation modulus according to the plate load tests and geotechnical monitoring data is proposed.Materials and Methods. The research comprised:– analysis of the existing approaches and methodologies for the subfoundations and foundations design on the subsiding soils;– numerical experiments, including calculations according to the normative methodology, which implied variation of the original data of both the initial properties of soils and technological parameters of stabilisation, as well as statistical processing of the results;– analysis of the carried out earlier by the authors geotechnical monitoring results of the buildings built on the stabilized soils and experimental study of the deformation properties using a patented device;– determining the main factors having influence on the design solutions for the subfoudation soils and building foundations strengthening under a complicated set of operational loads and establishing a new dependence of the stabilised soil deformation modulus on the initial soil deformation modulus and percentage of soil reinforcement.Research results. It has been established that the existing methodologies for calculating the stabilised subfoudation soils are not enough precise for determining the forecastable subsidence of buildings and structures, and the obtained design values do not always correspond to the factual deformations of subfoundations and foundations. The dependence of the stabilised subfoudation soil deformation modulus on the initial soil deformation modulus and percentage of soil reinforcement with the cement-sand mortar has been traced. A new calculating methodology has been developed based on determining the stabilised subgrade soil deformation modulus according to the data of the plate load tests using a patented device and geotechnical monitoring.Discussion and conclusion. It has been established that the deformation modulus of the soil mass stabilised by the cementation method depends non-linearly on percentage of soil reinforcement with the cement-sand mortar and the initial soil deformation modulus, and this dependence is described by a second-order surface equation of a general form. It is recommended to apply the discovered dependencies for designing the technological parameters of the subsiding soils stabilisation in the Rostov region conditions.

Stress-Strain State Assessment of Building Subfoundations Having Flexible Constructive Scheme in Irregular Soil Stratification

Introduction. One of the main problems in the operation of buildings and structures is possibility of their damage due to non-uniform deformation of subfoundation soil caused by the various natural and technogenic factors. To establish the possible character and degree of damage of the above-surface structures, it is necessary to calculate the value of subfoun- dation relative differential settlement at the level beneath the foundation bottom. The subfoundation settlement is calculated within the compressible soil thickness using the specific gravity values and soil deformation modulus. The increment of settlement is induced by the increase of vertical stresses in the massif and increase of soil deformability upon growth of moisture. The purpose of the study is to establish the dependence of the magnitude of the relative difference in settlement on the deformation properties of soils with uneven occurrence of layers in order to predict the nature of damage to above-ground structures.Materials and Methods. An example of subfoundation deformation calculations at the bottom level of the free-standing foundations of a building having flexible constructive scheme has been studied. A model of stratification of two heterogeneous geotechnical elements with a 1:4 boundary slope and differing physical and mechanical properties has been used. It has been assumed that one of the geotechnical elements has natural properties enabling the building foundations to rest on it without prior site preparation. Another geotechnical element has significantly worse properties. The calculations on determining the settlement have been made in accordance with the layer-wise summation methodology.Results. The regularity in alteration of the predicted settlement value depending on the ratio of firm and soft soils thickness in the irregular stratification has been established. It has been proven that the difference between the specific gravity values of the heterogeneous beds within 10 % does not affect the depth of compressible soil thickness if the calculation of settlement is made using the layer-wise summation methodology.Discussion and conclusions. The calculation results analysis of the subfoundation settlement of the equidistant column foundations was carried out, the engineering solution was proposed to ensure reliability per limit state groups.

Evaluating moduli of triaxial geogrid-stabilised sandy soil with lightweight deflectometer

Geogrid-stabilised soil has been widely adopted to enhance performance in transportation and infrastructure sectors. In this study, the performance of unstabilised and triaxial-geogrid-stabilised sandy soils in terms of dynamic deformation modulus and elastic modulus was measured using lightweight deflectometer (LWD) and plate load tests (PLTs), respectively. The objective of the study was to evaluate: (a) dynamic deformation modulus of sandy soils with different relative compactions from deflectometer testing and compare with the elastic modulus of sandy soils from PLTs for a given relative compaction of 97%; (b) modulus improvement factors (MIFs) of triaxial-geogrid-stabilised sandy soils through extensive laboratory testing and (c) compaction quality control of well-graded gravel using deflectometer testing through a field study. The triaxial-geogrid-stabilised sandy soil layer showed MIFs of 1.51 and 1.37 obtained from deflectometer and plate load tests corresponding to an embedded depth of 50 mm, respectively. The percentage differences in these values are in the range of 4–9% for all the embedded depths. Hence, an LWD can be used instead of a PLT as a quick and low-cost alternative for determining the MIF of geogrid-stabilised sand soil, both in the laboratory and in the field.

Experimental studies on compaction of soil with HAMM 3411 vibrating roller

Introduction. Mathematical modelling is used to assess the influence of various factors on the result of soil compaction by a vibratory roller. The verification of the mathematical model is carried out by comparing it with the results of the experimental studies. Expanding the list of the roller models in the experimental studies allows expanding the range of conditions for verification of the mathematical model. The article presents the results of field experimental studies of soil compaction by HAMM 3411 vibrating roller. The data on the change in the value of the dynamic soil deformation modulus Evd depending on the number of passes of the roller during compaction of sandgravel mixture with a layer thickness of 0.5 m have been obtained. The peculiarities that are reasonable to take into account when carrying out further experimental research are revealed.Materials and methods. The experimental studies of the scope of vertical movements of the roller, as well as vertical accelerations of the roller and its frame were carried out on a HAMM 3411 vibrating roller during compaction of a sand-gravel mixture. The result of compaction of the soil after each pass was estimated by the value of the dynamic deformation modulus Evd, measured using the ZORN ZFG 3.0 dynamic loading unit. In the experiment, vertical movements of the vibrating roller were recorded using a BAUMER OADM 13U6480/S35A laser sensor. Accelerations of vibrations of the vibrating roller and the roller frame were recorded by piezoelectric accelerometers of the AR2099-100 and AR99-100 models. When processing sensor readings, digital signal processing technology was used – low-pass filters with a limit frequency of 200 Hz.Results. The studies were carried out on two sites with different soil moisture. On a site with waterlogged soil in the range of Evd values = 10 ...13 MPa, the amplitude values of the vertical accelerations of the roller were in the range from +20 ... +45 to -25 ...-43 m/s2, and the frames in the range from +2.5 ...+5 to -2 ...-5 m/s2. The range of vibrations of the vibrating roller in the area with waterlogged soil was 3.3...4.8 mm. On a site with soil with close to optimal importance, in the range of values Evd= 18...28 MPa, the amplitude values of vertical accelerations of the roller were in the range from +36 ... +48 to -35 ... -40 m/s2, and frames in the range from +3.5 ... +6 to -2...-4.5 m/s2.Discussion and conclusion. The results show that the range of oscillations of the drum, as well as the amplitude values of vertical accelerations of the drum and the drum frame slightly increase with increasing soil deformation modulus Evd. The results of the experiment correlate with the studies conducted on the models of rollers DM-DM-617. When measuring values of Evd in one cross-section, the difference between measured values along the axis of roller’s movement and on the pneumatic wheel track reached 30%. When analyzing obtained results, it is necessary to take into account that in the experiment the actual frequency of oscillation of the roller was 18 Hz, instead of 27 Hz as stated in the technical specifications. With such reduction of frequency, the forced force of oscillations will decrease approximately 2.25 times. Results of the experiment will help in further verification of mathematical model of the roller and in carrying out experimental researches of similar character.

Аassessing the Distribution of Statistical Heterogeneity of the soil deformation modulus based on static soil sensing

Cone penetration testing (CPT) has become one of the most commonly adopted in situ tests for site investigations, due to its reliability and repeatability of the measurements and the potential for direct use in design. CPT data we performed to a depth 5m in sandy soils within an area of 50x50m2 of 232 datasets, the significant of cone resistance force were analysis used statistical methods. The heterogeneity of soil deformation modulus was vertical and horizontally in three-dimensional plane analyzed. Data was shows vertically heterogeneity soil deformation but horizontally not heterogeneity.

SIMULATION OF VIBRATORY PLATE INTERACTION WITH THE GROUND SURFACE

The paper presents a three-mass rheological model of the system "soil – vibration plate base – vibration plate frame". The rheological model makes it possible to reproduce different modes of interaction between the vibratory plate base and soil: with different types of plate decoupling and without decoupling. We verify this model by comparing the experimental values of the vertical oscillation span of the base and frame of the Zitrek CNP 20 vibrating plate with the previously calculated values. As a whole, the calculated values of the span of vertical oscillations of the base and frame of the Zitrek CNP 20 vibrating plate correlate with the experimental data in the range of the dynamic modulus of soil deformation of 13…30 MPa. During the experiment we used the rheological model and obtained results are as follows: the mass of the vibrating plate (50; 150; 250; 350; 450; 550; 650; 750 kg), the coefficient of the elastic resistance of soil (30; 60; 90; 120 MN / m), and the coefficient of viscous resistance of soil (100; 200; 300 kN • s / m). The total number of combinations of parameters was 96. The processed results of the computational experiment provide the regression dependences for calculating the maximum soil reaction force, the time of soil loading (increasing the values of the reaction force of soil) t1, and the time of soil unloading (decrease the values of the reaction force of soil) t2. The simulation results show that, within one exposure cycle, the soil loading time t1 is less than the soil unloading time t2. The ratio t1/t2 is influenced by the weight of the vibratory plate, as well as the factors of elastic and viscous resistance of soil. This feature (t1/ t2  1) is typical for both vibratory rollers and rammers, which is confirmed by the results of the relevant experimental studies. The obtained regression dependences of parameters Fs, t1, and t2 on the vibratory plate mass and the factors of elastic and viscous resistance of soil are important for calculating the distribution of stresses and strains on the depth of the compacted soil.

The bounding effect of the water retention curve on the cyclic response of an unsaturated soil

The water retention properties of soils present in formation layers of roads and railways continuously vary due to repeated traffic loads and periodic rainfall events. This is important because the accumulated deformation and resilient modulus of such soils under cyclic loading are profoundly affected by water retention properties. This paper discusses the cyclic and water retention response of a clayey sand subjected to repetitive cyclic loading and wetting stages. The results show that the accumulated permanent strains and resilient modulus of the tested soil are dependent on the suction level while the main wetting water retention curve of the soil dictates the variation of the suction measured during cyclic loading and wetting. This bounding effect of the water retention curve is found to be dependent on the void ratio where the suction can even increase due to the accumulation of strains under cyclic loading while the degree of saturation increases. This contradicts the suction reduction typically observed with an increase in the degree of saturation. A void ratio dependent water retention model is developed accounting for the observed bounding effect and employed to predict the measured suction during repetitive cyclic loading and wetting. The suction values predicted by the void ratio dependent water retention model are in good agreement with the experimental data. The predicted suctions are then used in semi-empirical formulations to obtain the accumulated permanent strains and resilient modulus. A better correlation between model predictions and experimental data is achieved where the suction values predicted by the void ratio dependent water retention model are used. The results imply that predictive frameworks proposed for the cyclic behaviour of road and railway formation layers require water retention counterparts that incorporate the bounding effect of void ratio on soil water retention curves.

Accumulation of irreversible deformation of soils as a result of repeated loading

Objective. The purpose of the study is to establish the patterns of accumulation of irreversible soil deformations from repeated loading.Method. When loading soils, the balance between external and internal forces is established gradually over a more or less long time. Therefore, with a single application of a cyclic load, such an equilibrium can be achieved only in a relatively long time.Result. An approximate method is proposed for calculating the magnitude of the deformation developed as a result of the action of a cyclic load. The cases are determined when it is necessary to take into account the viscous component of deformation and when the latter can be neglected. It has been established that when determining the deformation of soils that has developed during a single application of such cyclic loads that are characteristic of the process of their compaction by machines, in all cases, except for rolling them with rollers on pneumatic tires, the viscous component of deformation can be ignored.Conclusion. In a relatively short time of the load, the state of equilibrium can be achieved only in the process of soil deformation by repeated loading. With an increase in the number of loading repetitions, the soil gradually hardens, and the deformation decreases. This occurs both due to the irreversible and reversible parts of the deformation. Consequently, the soil deformation modulus increases from cycle to cycle.

Analysis of the Direct Shear Test and Microstructure of the Lunar Soil Simulant Solidified by Sodium Silicate

The lunar soil is an ideal building material for future lunar base construction. In order to improve the strength of lunar soil, basalt with similar composition to lunar soil was used to simulate lunar soil due to lack of real lunar soil, and the simulated lunar soil was reinforced with sodium silicate. In order to study the direct shear mechanical properties of the simulated lunar soil by sodium silicate solidification, a series of direct shear tests and SEM microstructure tests were carried out, and the shear stress-displacement whole process curve was obtained. Influence law of mechanical characteristic parameters such as shear strength, shear deformation modulus, peak deformation and energy dissipation was studied. The results of the direct shear test show that the shear stress-shear displacement curve of the sample changes from hardening to softening with the increase of sodium silicate content. The shear strength and shear deformation modulus of simulated lunar soil increased first and then decreased. When the sodium silicate content was 5%, the shear strength and shear deformation modulus reached the maximum, which were 560 kPa and 7224 kPa, respectively. The addition of 5% sodium silicate increases the energy dissipation coefficient of the simulated lunar soil by about 12%. The microscopic test results show that the N-A-S-H gel and AFt formed by the alkali excitation and adsorption of the sodium silicate will connect the lunar soil simulant particles into a whole network structure, thereby improving the shear strength.

Indirect Determination of Soil Young’s Modulus in Lithuania Using Cone Penetration Test Data

Simplified methods based on cone penetration test results are commonly used to determine soil deformation modulus, depending on the engineering geological and geotechnical conditions and the complexity of the computational approach. This paper reviews some empirical equations based on the results of the cone penetration test and gives recommendations for the assessment of Young’s modulus, oedometric modulus and residual modulus from the cone penetration test result, according to the Lithuanian technical requirements and other standards. Theoretical interpretations of results are presented together with practical examples for coarse and fine soils, limits of empirical equations application are explained.

Deformation Modulus of Plastic-Frozen Soil According to Pile Testing

Deformation Modulus of Plastic-Frozen Soil According to Pile Testing

Influence of spudcan penetration on the stability of adjacent steel cylinder in sand

ABSTRACT A large-diameter thin-walled steel cylinder as the protective structure of a submarine production system is vulnerable to the spudcan penetration because of its shallow buried depth and large foundation size. Centrifuge model tests are carried out to investigate the behaviour of steel cylinders caused by spudcan penetration. Then, CEL method verified by centrifuge test is used to analyse the influence of spudcan penetration on the stability of steel cylinders under different spudcan-cylinder clearances. The results show that the deformation mode of the adjacent cylinder is affected by comprehensive factors such as spudcan-cylinder clearance, spudcan penetration depth, soil deformation modulus, and soil strength. The displacement and stress of the cylinder decrease exponentially with the increase in the spudcan-cylinder clearance. The affected distance of the spudcan penetration on the cylinder can reach more than two times the spudcan diameter.

Сomparative analysis of methods for calculating stamp modules of soil deformation

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 comparative analysis of methods for determining the mechanical performance of macrofragmental soils

Many researchers, including Marachi, Frost, Varadarajan, Mojtaba, Gupta, Kuznetsov and others, have investigated the mechanical properties of coarse clastic soils. In this work, two methods were considered to determine the strength and deformation characteristics of coarse clastic soil.The first method is based on the determination of normative values for the mechanical properties of coarse clastic soils based on their physical characteristics (developed by the Far Eastern Research Institute for Structural Design and Technology (FERISDT)), and the second method is based on consolidated-drained (CD) tests in a triaxial compression device at five different values of hydrostatic pressure. According to the results of the study carried out in accordance with the two methods, a significant difference in the values of specific cohesion and deformation modulus of the coarse clastic soil was obtained.The values of specific adhesion obtained by FERISDT method are nearly two times lower than those obtained by triaxial tests. While the specific cohesion has been largely influenced by aggregate percentage, the values of in-ternal friction angle and the modulus of deformation changed only slightly.

Effect of the dewatering on the surrounding terrains during the construction of Metrostation 9-III of the Sofia Metropoliten

The international practice often faces significant settlements of terrains and structures due to dewatering. This study presents of the dewatering impact during the construction of Metrostation 9-III from the Sofia Metropoliten on the surrounding terrains and buildings. The subsidences are quantified for specific values of the soil deformation modulus and varying values of the soil hydraulic conductivity.