The Use of Geotechnical Methods to Determine the Strength Parameters of the Substrate in Terms of Operation and Safety of Mortar Use

During firing from a mortar, an important issue is the parameters of compressibility of the ground on which the mortar is placed. This affects the operation of the mortar (including safety). During the qualification tests of the mortar, the influence of different types of substrate on its strength and work during shooting should be examined. Until now in the Polish standardization documents was no clear description about the substrate parameters used for this kind of tests. Analysis of the literature also did not allow to determine the dependence of the mortars displacement in the function of the type of substrate and its geotechnical parameters. Therefore, the authors carried out analytical and experimental analysis of the use of geotechnical methods to determine the parameters of the substrate for mortar testing. The paper presents the proposed types of standardized soil and their research methods. Preliminary tests were also carried out using the prescribed measurement methods and a comparative mortar firing test. Subsequently, an analysis of the results was carried out and the possibilities of using the proposed methods of measuring the parameters of soil compressibility were determined.

Evaluation of the Organic Soil Compressibility from In-Situ and Laboratory Tests for Road Application

Organic soil is characterised by high compressibility and should be improved so that it can be used for construction. The use of every method of soil improvement requires knowledge of the compressibility parameters. One of these parameters is the constrained modulus. The constrained modulus can be determined using laboratory or in-situ tests. In this study, the constrained modulus of organic soil was determined using oedometer and piezocone tests (CPTU). The author analysed subsoil under an approximately 250 m section of a designed road in north-eastern Poland. The constrained modulus of organic soil sampled from four different depths was determined in oedometer tests. Piezocone tests were conducted at 18 points located every 15 m along the length of the section concerned. To determine the constrained modulus based on the cone resistance from CPTU tests, the knowledge of the α and αM coefficients is needed. For the tested soil, the optimal range of the α coefficient from 0.4 to 0.7 was determined. The αM coefficient ranged from 0.4 to 0.8. The value of the constrained modulus of organic soil obtained from the oedometer tests, depending on the effective stress, ranged from approximately 100 kPa to 400 kPa. The constrained modulus of the tested soil decreased with depth, which both research methods proved.

A Deviatoric Softening Model to Simulate Compressibility Properties of Soft Clays

Soft clays are often associated with high compressibility due to their high void ratio, low shear strength, and creep behavior. Structures built on top of it can experience excessive settlement issues over a long period of time. The prediction of these settlements has attracted attentions from many researchers for over a century, but accurately predicting them still remains a difficult issue due to complex properties of soft clays, including plasticity, viscosity, anisotropy, soil structure and so forth. Therefore, studying the compressibility of soft clay is of significant importance. This dissertation aims to investigate the influence of plastic deviatoric strains on the compressibility of soft clays. First of all, the dissertation reviews a number of published incremental anisotropic consolidation tests on Finnish clays. The results demonstrate the dependence of soil compressibility on stress ratios. Based on the result, a modified yield surface size deviatoric softening law has been introduced. This softening law describes yield surface softening to be related to plastic deviatoric strain increments. Secondly, a new model named MEVP-DS, has been incorporated into the framework of Yin’s elaso-viscoplastic model to consider deviatoric softening, destructuration, and yield surface anisotropy of soft clay. Furthermore, the verification of MEVP-DS has been done through three phases. Phase one is the simulation of published incremental anisotropic consolidation tests on intact Finnish clay samples. The model results demonstrate MEVP-DS successfully captures the soil compressibility in response to different stress ratios. Phase two is the application of MEVP-DS in modeling 1-D consolidation tests on sensitive Champlain Sea clay. Model results highlight that using MEVP-DS is beneficial for predicting the compressibility and excess pore pressure response of the clay subject to constant rate of strain loading. Phase three is the application of MEVP-DS in simulating a real embankment dam on Champlain Sea clay. MEVP-DS not only simulates 40-year settlement measurements of the dam reasonably well, but also improves the prediction of lateral spreading of the dam. In summary, the MEVP-DS model proposed in this dissertation has shown to improve the simulation of soil compressibility of soft clays subject to 1-D, anisotropic and more complicated loading conditions.

A Deviatoric Softening Model to Simulate Compressibility Properties of Soft Clays

Soft clays are often associated with high compressibility due to their high void ratio, low shear strength, and creep behavior. Structures built on top of it can experience excessive settlement issues over a long period of time. The prediction of these settlements has attracted attentions from many researchers for over a century, but accurately predicting them still remains a difficult issue due to complex properties of soft clays, including plasticity, viscosity, anisotropy, soil structure and so forth. Therefore, studying the compressibility of soft clay is of significant importance. This dissertation aims to investigate the influence of plastic deviatoric strains on the compressibility of soft clays. First of all, the dissertation reviews a number of published incremental anisotropic consolidation tests on Finnish clays. The results demonstrate the dependence of soil compressibility on stress ratios. Based on the result, a modified yield surface size deviatoric softening law has been introduced. This softening law describes yield surface softening to be related to plastic deviatoric strain increments. Secondly, a new model named MEVP-DS, has been incorporated into the framework of Yin’s elaso-viscoplastic model to consider deviatoric softening, destructuration, and yield surface anisotropy of soft clay. Furthermore, the verification of MEVP-DS has been done through three phases. Phase one is the simulation of published incremental anisotropic consolidation tests on intact Finnish clay samples. The model results demonstrate MEVP-DS successfully captures the soil compressibility in response to different stress ratios. Phase two is the application of MEVP-DS in modeling 1-D consolidation tests on sensitive Champlain Sea clay. Model results highlight that using MEVP-DS is beneficial for predicting the compressibility and excess pore pressure response of the clay subject to constant rate of strain loading. Phase three is the application of MEVP-DS in simulating a real embankment dam on Champlain Sea clay. MEVP-DS not only simulates 40-year settlement measurements of the dam reasonably well, but also improves the prediction of lateral spreading of the dam. In summary, the MEVP-DS model proposed in this dissertation has shown to improve the simulation of soil compressibility of soft clays subject to 1-D, anisotropic and more complicated loading conditions.

THE EFFECT OF TEMPERATURE ON THE ENGINEERING PROPERTIES CONSOLIDATION BEHAVIORS OF SOFT SOIL

Research on soil behavior due to changes in heat temperature in the soil mass is still relatively small. Even though, the phenomenon of increasing temperature in the soil mass is frequently occured. For example, there is an increase in temperature in the ground besides the problem of heat propagation under the road due to land fires, as well as the presence of waste heat from nuclear power plant in the soil medium, the operation of electric cables in the ground which causes heat, and the gas pipelines and oil pipes embedded in the ground, which generates heat around it, as well as thermal energy storage that are embedded in the soil. This research was conducted to get answers to how the behavior of the curve of the clay soft soil consolidation is due to changes in temperature. Mainly to get knowledge about the effect of temperature on changes in the value of mechanical parameters of soil consolidation, such as clay soft soil compression index (Cc), swelling index (Cs), volume change coefficient (mv), coefficient of consolidation (Cv), and hydraulic conductivity (k) of clay soft soil. In conducting the research, the material used was clay soft soil in undisturbed condition originating from a swampland locating in South Kalimantan, Indonesia, while the main tool used was a modified consolidation test device by adding an artificial heating device whose temperature could be adjusted with a temperature control device and temperature sensor. The temperatures applied to the test specimens were 40oC, 60oC 75oC, and 85oC. The results showed that changes in temperature in the soil could affect the compressibility of the soil, where the higher the temperature (heat) of the soil, the greater the soil compressibility. The increase in temperature in the soil causes an increase in the value of soil compressibility parameters such as the soil compression index (Cc), the coefficient of consolidation (Cv), and the swelling index (Cs). The value of compression index (Cc) of clay soft soils has a greater increase than the increase in other compressibility parameters when the temperature of clay soft soil increases (hot). In addition, the presence of high soil temperatures (hot conditions) in the soil can reduce changes in soil volume, where the volume change coefficient (mv) of clay soft soil tends to decrease if the soil temperature increases. Changes in soil temperature also affect soil permeability, where the seepage properties of clay soft soil tend to increase along with an increase in temperature in the soil.

Effect of Adding Sand on Clayey Soil Compressibility

The effect of adding sand on clayey soil compressibility is investigated in this study. Four different percentage of clay-sand mixtures are used; 100% clay with 0% sand named 100C, 30% clay with 70% sand named 30C-70S, 15% clay with 85% sand named 15C-85S, and 100% sand named 100S. The used clay was obtained from Baghdad city in Iraq and classified as CH soil, while the used sand was taken from the sand quarry in Al-Khider area from Al-Muthana Governorate in Iraq and classified as SW soil. The initial dry unit weight for all mixtures is 18 kN/m3. The results show that the variations of the soil compressibility properties with soil components content changes almost linearly The results show that the preconsolidation stress (Pc) decreases with 19% and 38% and the rebound index (Cr) decreases with 4 and 53% and the compression index (Cc) decreases with 39 and 68% as the sand percentage increases with 70 and 85% respectively. Finally, predicted (fitting) Equations are achieved for the change of the soil compressibility properties with clay content with good agreement.

LAND SUBSIDENCE STUDY IN KENDAL DISTRICT, CENTER JAVA

The need for information about disaster prone areas in Indonesia began to be felt very urgently since the natural disasters that occurred in many places in Indonesia. One of the information needed is information related to the area of land subsidence disaster. Kendal Regency is one of the areas located along the north coast of Java which is generally composed of alluvium deposits that have not been maximally consolidated, so they have high soil compressibility. These conditions indicate that compaction of the land naturally is still ongoing, so that if there is excessive overloading it will lead to a process of land subsidence regionally. By knowing the value of land subsidence and the areas that experience it, it is expected to be able to support regional planning, planning and development of basic infrastructure / facilities, housing / settlement planning as well as regional economic development in efforts to mitigate land subsidence.

Effect of soil compressibility on the structural response of box culverts using finite element approach

The structural response of box culverts to variable soil compressibility condition was studied in this paper. This was made possible by modelling the soil as springs, and varying the spring stiffness which was represented by the modulus of subgrade reaction of the soil. The results showed that the values of maximum bending moments for gravity actions on box culverts increased linearly with modulus of subgrade reaction, but remained within close values. The results also showed good agreement with results from literature for highly compressible soils. However, for incompressible soil condition, results from standard tables in literature were more conservative with about 10% difference for gravity actions, and 21% difference for lateral actions. The term ‘highly compressible’ that was used in literature for manual analysis was discovered to be more valid for lateral load cases than for gravity load cases. Subsequently, the variations of other action effects such as shear force, axial force, torsion, and soil spring settlement with modulus of subgrade reaction were also studied. Keywords: Box Culvert, Modulus of Subgrade Reaction, Soil Settlement, Staad Pro.