Strength Of Cemented Soil Research Articles

Effect of Solidification Mechanism of Nanometer Ore Powder Cement Soil on the Late Formation of Composite Foundation

The purpose of this paper is to study the influence of the solidification mechanism of nanometer ore powder cement soil on the late formation of composite foundation. Taking nanometer ore powder cement soil as the research object, six different gradients of nanometer powder powder are added, and each gradient has 3 parallel tests. First, use the orthogonal test method to statistically analyze the strength of the cement soil at different periods and different amounts of nano-powder powder, then use the pozzolanic reaction and XDR method to fit and analyze the solidification mechanism data of the nano-powder powder cement soil, and finally add It was analyzed whether the cement soil reinforced with nanometer ore powder and the original foundation soil can coordinate deformation and co-bearing to analyze the influence of composite foundation formation. Experimental data shows that with the increase in the amount of nanometer ore powder, the strength increases substantially linearly. When the time is 25d, = 30%, the maximum strength can reach 4.28 MPa, which is 3.72 times the strength of ordinary cement soil at the same age. After adding the nanometer ore powder, a large amount of calcium ions are consumed through the volcanic ash reaction. From the XDR data analysis, the particle diffraction intensity of the cement stone added with the nanometer ore powder is reduced by 25% compared with that of the ordinary cement stone.

Experimental Investigation on Unconfined Compressive Strength of Cemented Soils Admixed with Saturated GAC

This research investigated the compressive strength of cemented soils admixed with saturated granular activated carbon (GAC). The saturated GAC was obtained from the water filtration system. A series of unconfined compressive strength was performed on both compacted soil-cement specimens and compacted soil-GAC-cement specimens with GAC content of 30 percent. All specimens were prepared by compaction with energy equivalent to the modified Proctor test. The results from modified Proctor tests showed that the maximum dry unit weight and the optimum moisture content of soil-GAC sample was less than those of soil sample. From the unconfined compression tests, there was tiny development of strength for both types of specimens with cement content of 1 percent throughout the curing period of 28 days. For both types of specimens with cement content of 2 and 3 percent, the significant development of strength occurred after curing for 3 days. The strength of specimens typically increased with increasing cement content. Generally, the strength of compacted soil-GAC-cement specimens was less than that of compacted soil- cement specimens. It was also observed that the relationships between normalized compressive strength ratio and curing period was unique for the specimens with the same cement content.

Experimental Study on Mechanical Properties and Micro-Mechanism of All-Solid-Waste Alkali Activated Binders Solidified Marine Soft Soil

Utilizing granulated blast furnace slag (GBFS), coal fly ash (FA), and furfural residue incineration ash (FRIA) as pozzolanic materials, then activated with calcium carbide residue (CCR) respectively to prepare all-solid-waste alkali activated binders (ASW binders). The laboratory tests were performed to research the effects of pozzolanic materials with different reactivity on the macro- and micro- characteristics of solidified marine soft soil. Results show that the mechanical properties and alkali-activation process of ASW binders solidified soil was determined mainly by the reactivity of pozzolanic materials, the higher reactivity of the pozzolanic materials in ASW binders couldn’t change the main hydration products, however, it would accelerate the hydrate reaction. The degree of hydrate reaction increased, the microstructure became denser with the increase of the reactivity of the pozzolanic materials in ASW binders solidified soil, on the macro- side, the strength and deformation modulus of the solidified soil increased, meanwhile, the brittleness of the solidified soil will be more obvious during the deformation resistance process. ASW binders (CCR:GBFS=1:1) solidified soil could reach the strength of cemented soil under the same conditions.

Research on prediction of cement-soil cohesion based on strength test

In order to accurately predict the cohesive of cement-soil and better reflect the shear strength of cement-soil, through indoor strength tests and theoretical analysis, the influence of cement mixing ratio on shear strength and unconfined compressive strength is discussed. In the commonly used cement mixing ratio range (5%-30%), prediction formula of cohesive and unconfined compressive strength is proposed. The cohesive prediction model based on cement mixing ratio and age is further established. The results show that the unconfined compressive strength and cohesive strength of cement-soil increase with the increase of cement mixing ratio and curing age. There is a good linear relationship between cohesion and unconfined compressive strength. Based on nonlinear regression analysis, the prediction model of cohesive under the influence of multiple factors fits well with the test results.

Three point bending flexural strength of cemented soil reinforced by PVA and Jute fiber

In this paper, the flexural and post-cracking performance of deep soil–cement column reinforced by Jute fiber and PVA fiber, respectively were investigated. The results indicates that both Jute and Polyvinyl alcohol fiber significantly improved the first crack flexural strength and peak flexural strength. In addition, the fiber content play a critical role for enhancing the post-cracking performance of specimens, the peak strength ratio, residual flexural strength ratio, ductility index and energy absorption capacity increased with increasing fiber content. Jute fiber group exhibited slightly better in terms of energy absorption capacity.

Analysis of the influence of different soil properties on the strength characteristics of cement soil

When deep cement mixing method (DCM) uses cement as solidified material to treat marine soft foundation, the strength of soil is different due to the diversity of water content, void ratio and particle fineness. Based on the Pearl River Estuary DCM project, this paper uses a variety of PO.42.5 cement and marine soft soil in the Pearl River estuary area to carry out indoor mix proportion tests. There are four kinds of soil: flowing mud, silt, muddy soil and silt. The test results show that the strength of cement soil in different soil layers is diversity. The effect of cement solidification treatment on silt and muddy soil is good, followed by silt, and flowing mud is slightly poor. The selected PO.42.5 cement can meet the strength requirements of DCM.

Cyclic shear characteristics of marine cement soil under stress path with bidirectional shear stress

Under seismic loading, marine soil experiences horizontal shearing in two directions with different shear directions and amplitudes. It is therefore of considerable practical relevance to study the deformation behavior of marine cement soil under bidirectional shear loading. In this study, a series of cyclic simple shear tests were carried out to investigate the undrained deformation behavior of marine cement soil. The cyclic strain, stiffness softening, and cyclic strength were found to be significantly related to the phase difference and cement content. Cyclic shear strain accumulation increases as the number of cycles increases, and the emergence of inflection on the shear strain curve can be considered a suitable failure criterion for cement soil. The turning strain decreases as the cement content increases, and the phase difference decreases. With a decrease in cement content and an increase in phase difference, the rate of cyclic degradation and development of shear strain significantly increased. It was observed that the cyclic strength of cement soil increases with the cement content and decreases as the phase difference decreases.

Splitting Tensile Strength of Cement Soil Reinforced with Basalt Fibers.

Due to low splitting tensile strength, cement soil is more likely to experience dry shrinkage and cracking in practical engineering. In this study, the mixing procedure of the cement soil reinforced with basalt fibers was investigated; the influences of cement content, curing time, basalt fiber content and length on the splitting tensile strength of the cement soil reinforced with basalt fibers were studied; and the correlation of the splitting tensile strength vs. the compressive strength of the cement soil reinforced with basalt fibers was discussed. The contribution of basalt fibers on performance improvement of the cement soil was also addressed based on the microstructural analysis and the toughening mechanism exposition. Results indicate that the best mixing method for the cement soil reinforced with basalt fibers is to mix the muddy silty clay with basalt fibers first, then with cement slurry. The increase of cement content and curing time can improve the splitting tensile strength of the cement soil effectively. The splitting tensile strength of the cement soil increases first and then decreases with the content and length of basalt fibers. The optimal content and length of basalt fibers for the cement soil are 0.4% and 12 mm, respectively. The relationship between the splitting tensile strength and the compressive strength of the cement soil reinforced with basalt fibers can be described as a linear relationship with the correlation coefficient of 0.245 and the determination coefficient of 0.990. The contribution of basalt fibers on the toughening mechanisms of cement soil shows that the fiber-matrix interaction would be the dominant effect to control the tensile strength of the soil-cement-fiber composites. The results of this study can provide a reference for the design and application of cement soil reinforced with basalt fibers in actual engineering.

Hydraulic Conductivity and Compressive Strength of Cemented Soils

The addition of cementing agents is a well-known way of stabilizing an unsatisfactory soil for design parameters. This research evaluates three soils, namely pink kaolin silty soil, Botucatu weathered sandstone residual soil and Osorio uniform sand, stabilized with Portland cement type III. Hydraulic conductivity measurements were performed with a flexible wall permeameter, following the recommendations of ASTM D5084; unconfined compressive strength tests were also carried out, in accordance with ABNT NBR 12025. The result of this research observed a gain in compressive strength, best described as a linear gain with the increase in cement content, and as a power function as porosity decreases. The measured hydraulic conductivity observed a general reduction, similarly, with a linear decrease in regards to increasing cement content and decreased as a power function in regards to decreasing porosity. The possible correlation of the output variables investigated suggests the existence of a grid-like relationship, which can be potentially useful in earthworks and more general applications.

The effect of cemented soil strength on the frictional capacity of precast concrete pile–cemented soil interface

The pre-bored grouted planted (PGP) pile is a composite pile consisting of a precast concrete pile and the cemented soil around the pile. Thus, the PGP pile shaft capacity is affected by the pile–cemented soil interface and the strength of the cemented soil formed around the pile. In this paper, a series of shear tests were conducted to investigate the frictional capacity of the precast concrete pile–cemented soil interface, and the strength of cemented soil and its effect on the interface frictional capacity. The test results show that the frictional capacity of precast pipe pile–cemented soil interface is largely dependent on the cemented soil strength, and the peak skin friction of the interface increases from 7.58 to 204 kPa with the cemented soil strength increasing from 65 to 1500 kPa. An adhesion factor is proposed to correlate the peak skin friction of the precast pipe pile–cemented soil interface and cemented soil strength. The adhesion factor is found to range from 0.116 to 0.141 corresponding to the range of cemented soil strength from 65 to 1500 kPa. It was also noted the failure at the pile–cemented soil interface is brittle. The scale effect also exists in the pile–cemented soil interface shear test, and the scale effect factor is 1.9 when the pile diameter decreases from 85 to 37 mm. Accordingly, the design of PGP pile should avoid approaching the frictional capacity of the pile–cemented soil interface.

Tensile strength of sands treated with microbially induced carbonate precipitation

During large earthquake events where bending moments within soil cements are induced, the tensile strength of cemented soil may govern the deformational behavior of improved ground. Several studies have been conducted to assess the tensile strength of artificially cemented sands that use Portland cement or gypsum; however, the tensile strength of microbially induced carbonate precipitation (MICP)-treated sands with various particle sizes measured through direct tension tests has not been evaluated. MICP is a biomediated improvement technique that binds soil particles through carbonate precipitation. In this study, the tensile strength of nine specimens were measured by conducting direct tension tests. Three types of sand (coarse, medium, and fine) were cemented to reach a heavy level of cementation (e.g., shear wave velocity of ∼900 m/s or higher). The results show that the tensile strength varies between 210 and 710 kPa depending on sand type and mass of carbonate. Unconfined compressive strength (UCS) tests were performed for each sand type to assess the ratio between tensile strength and UCS in MICP-treated sands. Scanning electron microscopy (SEM) images and surface energy measurements were used to determine the predominant failure mode at particle contacts under tensile loading condition.

Early mechanical properties of high calcium fly ash cement soil

In order to improve the comprehensive utilization rate of industrial waste fly ash materials, this paper attempts to add high calcium fly ash to cement soil to study the effect of high calcium fly ash on the performance of cement soil materials and its strength formation mechanism. By designing the cement soil strength test and the excitation test, the early stage strength of the cement soil material can be improved by adding a certain amount of high-calcium fly ash and activator, which provides the application of high-calcium fly ash in engineering. It is also a supplement and improvement of the theoretical application system of fly ash materials.

Test Research on Mechanical Property of Cemented Soil Strengthened with Basalt Fiber

To enhance the mechanical property of cemented soil, this paper discusses the way of improving the mechanical performance by incorporating basalt fiber into cemented soil. Unconfined compressive strength test is conducted on cemented soil with basalt fiber of different proportions, and the results show that the incorporation of basalt fiber can significantly improve the compressive strength of the cemented soil samples at different ages, but its strengthening effects weaken steadily with the increase of fiber amount. The incorporation of basalt fiber can enhance the plasticity of cemented soil, and the sample at its peak stress can still bear some loading, with some residual strength existing, propitious for the enhancement of engineering safety and stability. Additionally, the relations between the compressive strength and ages of cemented soil with basalt fiber of different proportions are established based on the experiment results, which can provide some references for practical projects.

A study on the mechanical properties of cement soil added with ferronickel slag

Unconfined compressive strength test was employed hereby to study the effect of ferronickel slag content and mineral powder content on strength performance of cement soil. In the experiment, 0%, 10%, 20%, 30% and 40% ferronickel slag were added into the cement soil, respectively, to figure out the comparatively better content of ferronickel slag was 20%. The experiment results also indicate the addition of ferronickel slag also significantly affected the early strength of cement soil, but as the time proceeded, the strength of cement soil added with ferronickel slag fell less quickly as before.

Dynamic Mechanical Properties and Fractal Characteristics of Polypropylene Fiber-Reinforced Cement Soil under Impact Loading

This paper aims to study the dynamic mechanical properties, failure patterns, fractal behaviors, and energy dissipation of polypropylene fiber-reinforced cement soil under impact loading. Dynamic compression tests for reinforced cement soil with different polypropylene fiber contents of 0%, 0.4%, 0.8%, and 1.2% were conducted using a 50 mm diameter split Hopkinson pressure bar (SHPB) device. The static and dynamic stress-strain curves, dynamic strength increase factor (DIF), fractal behaviors, and energy dissipation properties of polypropylene fiber-reinforced cement soil were investigated and analyzed. The experimental results indicated that the dynamic strength increase factor (DIF) of cement soil increases firstly and then decreases with the increase of polypropylene fiber content from 0% to 1.2%. The maximum dynamic compressive strength of cement soil was obtained with adding 0.8% polypropylene fiber. With the increase of polypropylene fiber content, the average particle size of cement soil fragments has an increasing trend, whereas the fractal dimension presents a decreasing trend. Besides, the fragmentation degree of cement soil decreases correspondingly with the increase of polypropylene fiber content. The fractal dimension value has a linear relationship with the polypropylene fiber content and a decreasing exponential relationship with the average particle size. The absorbed energy per unit volume of cement soil presents an increasing trend firstly and a decreasing trend subsequently as the polypropylene fiber content increases from 0% to 1.2%. When the fractal dimension of cement soil is kept in the range of 2.04 to 2.15, the absorbed energy per unit volume of cement soil increases first and then decreases. The absorbed energy per unit volume of cement soil has a quadratic parabola relationship with polypropylene fiber content and fractal dimension, respectively. At last, the relationship of the absorbed energy per unit volume, fractal dimension, and polypropylene fiber content can be established, which can be used in the studies of dynamic behaviors and fractal properties of the fiber-reinforced cement soil under impact loading.

Effect of Polypropylene Fiber on Frost Resistance of Cemented Soil

Polypropylene fiber is widely used as a reinforcing material in composite materials of various engineering projects, because it has high strength and corrosion resistance. In this study, with the purpose of examine the impact of discrete polypropylene fiber on frost resistance of cemented soil, cemented soil treated with polypropylene fiber is used as the research sample. Firstly, the impact of curing time, fiber content and length on the strength of cemented soil has been considered. And then, the frost resistance characteristics of cemented soil reinforced by polypropylene fiber with the content of 0.5% have been investigated. The results show that with the development of curing time, the strength of cemented soil increases logarithmically. By adding an appropriate amount of polypropylene fiber, the strength of the specimen may be improved. In this study, cemented soil reinforced by polypropylene fiber 0.1% in content and 3 mm in length has the best reinforcement effect. After 21 cycles of freezing and thawing processes, a sharp decline in strength of cemented soil without fiber, and the strength loss ratio is up to 45%. There are cracks in the specimens, and some of the specimens have broken off. Differently, after 21 freeze-thaw cycles, the strength of the cemented soil with fiber decreased less, and the strength loss ratios are between 1 and 13%, and there are only small cracks on the surface of specimens. The results show that adding discrete polypropylene fiber is a suitable method to prevent the generation and development of internal cracks in the cemented soil during freezing and thawing, thereby improving the frost resistance. These results can be used as a reference for the application of cemented soil reinforced with fiber in seasonal frozen regions.

Correlation between Unconfined Compressive Strength and Penetration Index Obtained from DCP Tests for Cemented Lateritic Soils

This paper presents the relationship between the dynamic cone penetration (DCP) test results and the unconfined compressive strength of lateritic cemented soils. A series of DCP tests and unconfined compressive strength was performed on lateritic cemented soil. The soils sample used in this study was lateritic soil. The test results for the DCP tests are presented in terms of penetration index. It can be observed that the penetration index decreased with increasing curing period and cement content. Moreover, the unconfined compressive strength of cemented soils increased with curing period and cement content. The relationship between unconfined compressive strength and penetration index is presented. A unique relationship for unconfined compressive strength can be obtained.

Effect of VOCs pollutants on strength of cemented soil

Based on the soil conservation project of a chemical plant in Zhenjiang, the effects of volatile organic compounds (VOCS) pollutants on the strength of cement soil were studied experimentally. Xylene was utilized for indoor experiment. The specimen was made of water, xylene solvent, gray yellow clay and 42.5 ordinary Portland cement in a certain proportion. Firstly, the influence of the content of xylene on the unconfined compressive strength of cemented soil with time was analyzed, and then the effect of cement blending ratio on the unconfined compressive strength of samples containing xylene was studied with the increase of time. The results showed that the unconfined compressive strength of cement-soil samples increase with the increase of time and decreased with the increase of xylene content in similar curing time; the same xylene incorporation and the unconfined compressive strength of cement soil samples increased with the increase of cement incorporation ratio. In addition, the author also verified the impact of VOCs pollutants on cement-soil retaining walls by simulating actual engineering, and proposed two solutions which were expected to advise the engineering.

Laboratory test on long-term deterioration of cement soil in seawater environment

Laboratory tests were conducted to study the effects of curing time, cement ratio and seawater pressure on cement soil deterioration formed at simulative marine soft clay sites. Deterioration depth was determined on the basis of characteristics of penetration resistance and penetration depth curves, and the deterioration depth of cement soil with the cement ratio of 7%, reached 31.8 mm after 720 d. Results of research indicated that deterioration extended quickly under seawater environment and the deterioration depth increased with the prolonging curing time. In addition, the water pressure could speed up deterioration. With the increase of cement content, the strength of cement soil increased obviously. At the same time, the deterioration depth decreased significantly. The concentration of calcium ion in the cement stabilized soil increased with the increase of depth, while that of magnesium ion gradually decreased. The variations were consistent with energy dispersive spectrometer(EDS)analysis results, and the calcium concentration with depth was in a good consistency with strength distribution at long term. The results showed that the deterioration became more serious with the curing time, and it was related to calcium leaching.

Drained Shear Strength of Over-Consolidated Compacted Soil-Cement

AbstractThe use of cement as an additive to natural soil has been practiced for a long time in engineering projects. Chemical bonds generated as the result of cement hydration and pozzolanic reactions have been responsible for the increase in strength of cemented soils. The purpose of this research is to evaluate the effect of cement on residual strength of overconsolidated soil. Drained shear strength of overconsolidated compacted soil and soil-cement specimens consisted of 50% bentonite, 50% Aeolian sand with 3% by dry weight cement in as compacted (unsheared or intact); precut (residual) conditions were measured in a direct shear device after varying curing time. The cementation that occurred because of the addition of cement and the increase of curing time caused a remarkable increase of mobilized drained shear strength in both intact and residual conditions. A remarkable increase in cohesion intercepts c′, a negligible decrease in ϕ(oc)′ in intact condition, a negligible cohesion and noticeable incre...