Low Liquid Limit Research Articles

Soil‐Water Characteristics of the Low Liquid Limit Silt considering Compaction and Freeze‐Thaw Action

The soil‐water characteristic curve of silty soil in seasonal frozen area during freezing‐thawing process was studied in this study. By means of a laboratory test, specimens with different compaction degrees and different initial moisture content were prepared and put into the temperature change testing machine for freeze‐thaw action. The influence of different degrees of compaction and different times of freeze‐thaw action on SWCC of low liquid limit silt was analyzed, a V‐G model was used to fit the test data, and a set of fitting parameters with a reference value was obtained. At the same time, the change of microstructure between soil particles during the freezing‐thawing cycle is illustrated. The results showed that with the same water content and the same compactness, the matric suction of the test soil decreased with the increase of freeze‐thaw cycles. For the same number of freeze‐thaw cycles, the greater the compactness, the greater the matric suction of the soil. The V‐G model can well represent the SWCC of low liquid limit silt during the freeze‐thaw cycle.

Stabilizing Geotechnical Properties of Loess Soil by Mixing Recycled Polyester Fiber and Nano-SiO2

The present study investigated the effect of recycled polyester fiber in combination with nano-SiO2 as a new stabilizer for improving the geotechnical properties of the loess soil. In addition, it intended to evaluate the effect of adding recycled polyester fiber and nano-SiO2 on engineering properties of the soil, especially the maximum dry density and shear strength using silty loess with low liquid limit. To this end, three different combinations of fiber and nano-SiO2 ratios were used ranging between 2 and 6% in proportions of 33% and 50% for the total dry weight of the soil. Furthermore, three different combinations of fiber-soil ratios were employed which ranged between 0.5 and 1.5% for the total dry weight of the soil, as well as three different combinations of nano-SiO2 ratios ranging between 2 and 6% for the total dry weight of the soil. The results from the compaction test indicated that the maximum dry density of the stabilized loess decreased while the optimum water content increased by adding recycled polyester and nano-SiO2. Based on the results of the direct shear test, the shear strength improved by increasing the contents of the recycled polyester fiber and nano-SiO2 in the soil mixture. Thus, the addition of recycled polyester and nano-SiO2 improved the strength properties of the loess soil. In order to obtain the maximum increase in shear strength, the optimum content of the recycled polyester fiber and nano-SiO2 was 4% of loess soil dry weight in proportions of 33% and 50% in the mixture.

Study the Geotechnical Properties for Recent Deposits/AL-Fursan Area North of Tikrit

Four sites with different depth in AL-Fursan area/ North Tikrit city were selected for recent deposits sampling. The geotechnical properties of soil were tested and improvement of engineering properties of soil by cement was carried out. The geotechnical properties test results revealed that the moisture content ranges between (0.53 -1.45)% which is low because of sampling in summer season, while the grain size analysis show that the soil at the study area is coarse soil (sand) with fines. The soil type in the first site is clayey sand (SC), the second site contains sand with equal percentage of silt and clay (SC- SM) , the third and fourth site types are silty sand (SM). The specific gravity ranges between (2.46- 2.72) sites (1,2,3) are low liquid limit and low swelling index but the fourth site is moderate. The value of cohesion strength for the four sites are (16, 13, 1, 8)kPa respectively, sites (1) and (2) are moderate cohesion while sites (3) and (4) are non-cohesion, none plastic and un active.
 The low values of cohesion strength belongs to high percentage of coarse particles in the area. The values of internal friction angles ranges between (300- 370). The consolidation test results revealed that all sites were moderate compressive index except the first site which is low compressive and low swelling. The study area soil are neutral and high content of gypsum and soluble Dissolved salts and also high organic content. The soil improvement by cement tests results show increasing of cohesion and internal friction angle and the compaction test results show the samples are well sorted.

Physical characteristic analysis of unconsolidated sediments containing gas hydrate recovered from the Shenhu Area of the South China sea

Laboratory research based on the physical characteristics of unconsolidated sediments containing gas hydrate was carried out on hydrate-bearing sediment samples recovered from China National Offshore Oil Corporation (CNOOC) drilling expeditions in 2015 and 2017 at the station of LW3 in the northern part of the South China Sea. We herein have measured the gas composition, index properties, surface characteristics, thermal properties, and mechanical properties of these sediment cores drilled at different seafloor depths. Based on the measurement results, more than 99% of the gas composition is methane gas. The hydrate-bearing sediments recovered from Shenhu Area are non-diagenetic rock, the fraction of grain size which less than 40 μm was more than 90%. The results could provide useful guidance for potential sand-control system operations. Such small and consolidated particles indicated that the application of a novel solid fluidization mining method is viable and promising. The fine-grained layers were found to be mostly self-filtering and internally stable for the seepage flow during production. Gas hydrate mostly occurs in vein-type, and bioclastics consisting of marine planktonic diatoms and foraminifera were also found. The mineral components of the sediments were mostly quartz, clay minerals like illite and some feldspar like albite. The thermal conductivities changed from 1.4 to 1.77 W/(mK), which suggests that the isolated depressurization methods could exacerbate the problem of gas hydrate reformation or ice generation; thus, heat injection in wellbores should be combined for gas hydrate production strategies. The low liquid limit (38%) and plastic limit (24%) imply that stability of the production platform should be taken into account for avoiding submarine landslide impacts. The results of mechanical property analyses indicated that hydrate-bearing sediments at deeper sites have a relatively higher strength at hydrate layer of 120–133 mbsf in the Shenhu Area of the South China Sea.

Experimental Research of Low Liquid Limit Silt Stabilized by Lignin in the Flooding Area of Yellow River

Adding stabilizers is a common method to improve the engineering properties of problematic soil such as silt. Although many traditional stabilizers (cement, lime, fly ash, etc.) have been widely adopted for ground improvement, they often adversely affect the surrounding soil and groundwater environment. To seek an alternative stabilizer that could eliminate these disadvantages, this paper presents a study of low liquid limit silt in the flooding area of Yellow River stabilized by lignin (an industrial by-product). The compaction performance, compressive strength and water stability of the stabilized silt with lignin was studied through laboratory tests. Tests results indicate that lignin has a great potential to improve engineering properties of silt. The compressive strength of the stabilized silt increases with both the increase of lignin content and curing age. Moreover, lignin can effectively improve the water stability of silt, and the best content of lignin is 12% for the silt studied in this paper.

Micro–macro properties of plastic concrete anti-seepage wall materials mixed with low-liquid limit clay

In this study, the micro–macro properties of plastic concrete mixed with low-liquid limit clay were explored, including the mechanical properties, deformation, impermeability, triaxial stress–strain curve, hydration products, phase composition, and pore structure. The results showed that the strength of the plastic concrete decreased with the increase in clay content. When the clay content was 140 kg/m3, the compressive strength and elasticity modulus/strength ratio at 28 days were 3.77 MPa and 316, respectively. The average water-absorption rate of plastic concrete was 10.4%, and the relative permeability coefficient was about 10−7−10−8 cm/s. The stress–strain curves obtained from the triaxial test indicate softening behavior, and the volume change–axial strain curves indicate expansion. The variation in strength showed good linearity with the increase of confining pressure, and the corresponding model parameters were obtained. In addition, micro-analysis showed that the types of hydration products in the hardened paste with different clay contents were almost the same, but the intensity of each diffraction peak was different. As the curing age increased, the degree of hydration of the paste increased, internal pore diameter became smaller, and structural integrity was improved. This study aims to enable the use of local low-liquid limit clay resources to reduce engineering cost and adjust the performance of concrete.

One-dimensional normal compression laws for resedimented mudrocks

Abstract Four different empirical models used to describe the one-dimensional normal compression behavior of mudrocks have been evaluated by investigating the behavior of 15 different resedimented mudrocks. These mudrocks originate from a wide variety of geologic origins and were tested in the laboratory over an effective stress range of 0.1–100 MPa. The normal compression of silt-rich, low liquid limit mudrocks is best described by assuming a log-linear relationship between vertical effective stress, σ′v and void ratio. For smectite-rich, higher liquid limit mudrocks their behavior is better described by assuming a log-linear relationship between σ′v and porosity. The assumption of a log-log relationship between (1 + void ratio) and σ′v is not the most appropriate for any particular mudrock type, but gives a reasonably good description of compression behavior for all mudrocks, and is therefore ideal for situations in which the general composition of a sediment is unknown. For all mudrocks, the assumption of an exponential relationship between porosity and σ′v gives a very poor fit to the experimental data. As mudrocks undergo compression to high effective stresses, high liquid limit mudrocks display a much greater compressibility and a corresponding larger loss in porosity compared to more silt-rich mudrocks. The porosities of all materials tend to converge into a much narrower range above about 10 MPa, where all mudrocks display a similar compression behavior and a constant value of compression index of 0.21 regardless of their composition. At low effective stresses though, their compression behavior is strongly controlled by composition.

Mechanical Properties of Riverbank Soil in the Jingjiang Reach and the Characteristics of Flow in Pocket Collapse Area

Based on analyzing the field data and the experimental results, Mechanical properties of riverbank soil in the Jingjiang Reach and the characteristics of flow in the region of pocket collapse are discussed. It is calculated that riverbank of the Jingjiang Reach is characterized by a typical composite structure, covering the low liquid limit cohesive upper layer and the sandy lower layer. The cohesion of the cohesive soil increases first and then decreases with the increase of water content. The internal friction angle generally decreases with the increase of water content. The flow structure in pocket collapse area shows the intensive three-dimensional characteristics. The surface and vertical average velocity, the range and strength of the reflux increase with the increase of upstream flow discharge. Under different conditions of flow discharge, the vertical average velocity in pocket collapse area has a distributed feature of nearly linear or tiny oscillation along the relative direction of water depth. The research can provide the technical support for prevention measures of bank collapse.

水泥稳定低液限粘土回填路基试验研究

水泥稳定低液限粘土回填路基试验研究

Comparison of the Casagrande and Fall Cone Methods for Liquid Limit Determinations in Different Clay Soils

ABSTRACT The liquid limit (LL) is an important parameter for soil classification systems. The use of the cone penetrometer technique for measuring the liquid limit is an attractive alternative method since the percussion method is highly operator dependent. In this article, the importance of specifying the procedure and equipment used to determine the LL of a clay soil is highlighted using LL test results conducted on different clay soils. The results of LL, obtained by the percussion method proposed by Casagrande (LLc) and by the penetration cone method (LLp) on clay soils of different geological origins and plasticity were compared. The LLp values were determined using the British cone (20 mm fall cone penetration) method. The LLc values were determined using different hardnesses of Casagrande apparatus. The LL test results show that variations on the investigated methods depend on the mineralogy of the clay soil and the hardness base of the Casagrande cup. The data obtained for kaolinites and illites minerals or low LL soils yielded LLp>LLc. The results obtained for smectite minerals or soils with high LL values indicated LLp<LLc and a greater dispersion among the results. Statistical analyses of residues show that empirical LLp-LLc correlations through a linear regression analysis should be used with caution.

Relationship between the shrinkage crack characteristics and the water content gradient of compacted clay liner in a landfill final cover

Shrinkage cracking is the primary reason for the anti-seepage failure of compacted clay liner (CCL) in a landfill final cover. With a focus on the surface crack characteristics and the water content distribution of three CCLs with different liquid limits and their mineral compositions, experiments were conducted to investigate the cracking mechanism of a CCL during the drying process. The results showed that the total crack ratio (TCR), the sum of the surface shrinkage crack ratio (SCR) and the surface boundary shrinkage ratio (BSR), is a function of the surface water content of a CCL. The change in the TCR with surface water content is consistent with the soil shrinkage characteristic curve (SSCC). The surface SCR is a function of the surface water content gradient of a CCL. The variations in the SCR with the water content gradient can be divided into the following three stages: the crack open stage, the crack linear expansion stage and the crack linear close stage. The effect of sample size, surface boundary shrinkage and shrinkage cracking are the main deformations of CCL specimens with low and high liquid limits, respectively, during the drying process. An increase in the amount of clay minerals in CCLs enhances the soil shrinkage capacity, leading to an increase in the SCR under the same water content gradient. A unified linear relationship exists between SCR/Kj (where Kj is the slope of the SSCC) and the water content gradient in the crack linear expansion stage and the crack linear close stage for different CCL types.

Dynamics of sediments on a glacially influenced, sediment starved, current-swept continental margin: The SE Grand Banks Slope off Newfoundland

The SE Grand Banks Slope is unusual on the glaciated eastern Canadian margin in that it was remote from ice stream and glacial ice of the Laurentide Ice Sheet (LIS). It thus allows an analysis of the role of contour currents and landslides in sculpting the continental margin, processes that are largely masked where downslope proglacial sediment supply dominated. Detailed oxygen isotope, geotechnical, pXRF, and bulk sediment geochemical analyses were made on seven piston cores and were placed in context using multi-beam bathymetry and high-resolution seismic reflection profiles. Cores have a record of sedimentation back to MIS6 preserved in autochthonous sediment and slide blocks, contourites and mass-transport deposits (MTDs). Detrital‑carbonate-rich Heinrich layers (H) are present throughout the succession, but red mud layers of glacial meltwater origin from ice-streams in the SE sector of the LIS are identified only during MIS2 and late MIS3. Both layers allowed high-resolution correlation between cores. Sediments on the upper slope above H2 are condensed and the section above H1 is <50 cm thick, indicating that the powerful Labrador Current winnowed the section above H2. In contrast to the upper slope, approximately 3 to 5 m sediments were recorded in the mid-slope above H2 suggesting that the Labrador Current was weaker. Regional stratigraphic variations compared to Flemish Pass and Orphan Basin to the north suggest that NE Newfoundland sources of sediment played an important role and may have been previously underestimated. This study demonstrates that across-margin thickness variations reflect the character and distribution of the Labrador Current sediment transport system through time.Five horizons with MTDs with headscarps generally up to 25 m high are recognized in the upper 50–70 m. Thick MTDs are blocky in cores and in their seismic and bathymetric expression resemble spreads, with local thin mud clast conglomerates that ran out as debris flows over the contemporaneous seabed. Geotechnical data suggest that the seabed is stable under static conditions, although there is geological evidence for fluid escape and geotechnical evidence for underconsolidation. Weak layers along which failure took place are found somewhere around H3–H4 and at or near the top of H5 and MIS6. The low plasticity and liquid limit of the H layers make these layers susceptible to failure during cyclic loading. Episodic earthquakes are the most likely cause of failure.

Site Characterization for Construction Purposes at FUNAAB using Geophysical and Geotechnical Methods

Abstract Geophysical and geotechnical techniques were used to investigate the sub-surface information of a proposed site for a hostel construction at Federal University of Agriculture, Abeokuta. Ten vertical electrical sounding (VES) stations were adopted. Typical sounding curves obtained include the HA, KH, AKH and KQH types, of which the AKH-type consists of 40% of the survey points, and a maximum of five geo-electric sub-surface layers were delineated. Laboratory analyses were performed to investigate particle size distribution, Atterberg limit, compaction limit, California bearing ratio (CBR) and specific gravity. The CBR revealed that all soil samples, except L4, are mechanically stable and have high load-bearing capacity. The Atterberg limit test and the geo-electric section showed that the second layer of VES 4 is composed of sandy clay with high plastic index and low liquid limit, which may pose a threat to the foundation of any engineering structure. VES locations 5, 6 and 8 were identified as high groundwater potential zones suitable for optimum groundwater abstraction. The study area is suitable for both shallow and deep foundations, however VES 4 and VES 5 require reinforcement.

Large-scale test of sleeve valve pipe grouted overwet subgrades

Due to the intense capillarity action on low-liquid limit silt subgrade, the subgrade is often overwet. The technology of sleeve valve pipe grouting is an effective reinforcement method of the overwet subgrade. However, there are limited studies on the reinforcement mechanism and its effects. In this study, four large-scale subgrade models were set up. Distributions of moisture content and physical mechanical indexes of soil in different silt subgrades were analysed. Integral stiffness and deformation characteristics of the subgrades were studied by cyclic step loading tests. The subgrade models were excavated after tests to see the spreading pattern of the grout slurry. The reinforcement mechanism of the sleeve valve pipe grouting was analysed based on Vesic's cavity expansion theory. The results indicate that the integral stiffness and stability of the subgrade decrease due to the capillary action. The vertical plastic deformation of the wet subgrade rapidly increases with the increase in vehicle load. Sleeve valve pipe grouting produces bottom-expanded micropiles, and also horizontal reinforcement layers, which can block the capillary water from rising and form a space frame with the bottom-expanded micropiles to bear the load with the soil together. This increases the subgrade stability, and the reinforcing effect is more significant than with the traditional grouting technology.

Improvement of Uniaxial Compression of Soil with ZnO tetrapods

With the limitation of the land availability in major population centers and the availability of the land to be used as waste management sites, incite is required in improving the ground. Many soil stabilization techniques are available using conventional method. Here, we intend to report a method applying the nanotechnology for ground improvement. T-ZnO is used to improve the uniaxial compressive strength of silty-clay at low liquid limit. Silt soil passing 1mm sieve and T-ZnO between 0-5 wt% is used. It was found that with increasing percentage of T-ZnO up to a threshold, a significant improvement in compressive strength is observed which may be attributed to the peculiar tetrapod shape that acts as reinforcement among silt and clay particles.

Evaluating the effect of biological stabilization on landslide control at the edge of forest road

Landslide is one of the negative sides of building non-standard roads in forest areas. The aim of the present study was to assess the effect of biological stabilization on landslide at the edge of forest roads in south and north aspects. For this purpose, in Neka forest (Mazandaran province) three treatments including control, sliding and stabilized areas covered by 35-years-old even-aged alder trees were selected. Benchmarking and soil sampling were conducted during three periods including July, November after rainfall events and March after rainfall events. The results showed that the mean movement of landslide in north direction was 9 cm, while this value was 6 cm in south direction. Sliding in north direction was 32% more than that in south direction. Biological stabilization by alder in north and south direction caused a 33 and 66% reduction in landslide movement, respectively. The characteristics of soil mechanics were different between stabilized and sliding areas. Besides, the soil texture in north direction for control and stabilized areas was clay with high liquid limit (CH) and for sliding area it was clay with low liquid limit, while this value in south direction was CH for three treatments of control, stabilized and sliding areas. To plan biological stabilization, the mechanical characteristics of soil, site features, and appropriate plant species should be considered as important factors.

Mechanical Characteristics of Stabilized Clay under the Influence of both Acidic and Alkalic Additives

To study the influence of the coexistence condition of acidic and alkalic additives on the mechanical performance of stabilized clay based on the processes for obtaining the basic physical parameters of soil and analyzing the stabilization mechanism of ionic and alkalic soil stabilizers, an experiment on the mechanical behavior characteristics of stabilized clay was performed using different types of ionic and alkalic stabilizers through a series of laboratory tests. The following results are obtained. (1) Typical soil is low liquid limit clay, and the ionic stabilizer with an optimal content of 0.014% mass ratio to dry soil exhibits strong acidity. (2) As a result of its unique molecular structure, the double electric-combined water film becomes thin rapidly during compaction molding, in which the compactness of clay particle structure increases. (3) The 7-day unconfined compressive strength can be improved with different contents of the ionic stabilizer. (4) Except for the high lime soil mixture, the compaction degree of soil exerts a pronounced effect on the stabilization performance of an ionic stabilizer and the least compaction degree should be over 96%. (5) The unconfined compressive strength, indirect tensile strength, and freeze-thaw performance of the acid-alkali-stabilized soil demonstrate a gradually increasing tendency with an increase in curing time, however, the evolution characteristic of strength exhibits an advantageous superposition threshold value when compared to the alkali-stabilized clay. The neutralization reaction and oil membrane of soil particles will inhibit the later reaction processes of carbonation, pozzolanic, and hydration of lime-|cement-stabilized soil.

Improving the geotechnical properties of soft clay with nano-silica particles

This paper reports on an investigation into the effect of using nano-silica particles to improve the mechanical properties of clayey soil with low and high liquid limits. The engineering properties studied included Atterberg limits, maximum dry unit weight, optimum moisture content, California bearing ratio, consolidation and unconfined compressive strength. Nano-silica to soil ratios of 0·5, 0·7 and 1·0% were used. Both the Atterberg limits and California bearing ratio values improved with increasing nano-silica content. Increasing ratios led to a reduction in the plasticity index and an increase in the shrinkage limit. The reduction in soil settlement was attributed to a viscous gel in the soil–additive interaction, which resulted in an increase in the pre-consolidation stress of the stabilised soil. The test results showed that the viscous gel caused an increase in initial pre-consolidation stress of 70 kN/m2 for a soft clay soil to 300 kN/m2 for a soil stabilised with 0·7% nano-silica. Undrained compressive strength also increased by up to 56%. An increase in nano-silica content led to a reduction in failure strain but an increase in the elastic modulus of soils. Based on the results, it can be concluded that the addition of nano-silica improves the mechanical properties of clay significantly.

XRD and TGA, Swelling and Compacted Properties of Polymer Treated Sulfate Contaminated CL Soil

Abstract In this study, the effect of up to 4 % calcium sulfate contamination on the soil properties of a natural clay with low liquid limit (CL) soil with and without polymer treatment was investigated and compared to 6 % lime treated soil. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) methods were used to identify and quantify the changes in the contaminated CL clay soil. XRD analyses showed the major constituents of the soil were calcium silicate (CaSiO3), aluminum silicate (Al2SiO5), magnesium silicate (MgSiO3), and quartz (SiO2). With 4 % calcium sulfate contamination, the liquid limit (LL) and plasticity index (PI) of the CL soil increased by 30 and 45 %, respectively. The addition of calcium sulfate resulted in the formation of calcium silicate sulfate (Ternesite Ca5(SiO4)2SO4) and aluminum silicate sulfate (Al5(SiO4)2SO4). TGA analyses showed a notable reduction in the weight of calcium sulfate contaminated soil between 600 and 800°C, possibly due to changes in soil mineralogy. In addition, the total weight loss at 800°C for 1.5 % polymer treated soil was about 40 % less than the 4 % calcium sulfate contaminated soil, and it was similar to the weight loss observed in the uncontaminated CL soil. The maximum dry density of compacted soil decreased and the optimum moisture content increased with 4 % of calcium sulfate. The addition of 4 % calcium sulfate increased the free swelling of compacted soil by 67 %. The addition of 6 % lime resulted in the formation of ettringite (Ca6Al2 (SO4)3(OH)12·26H2O). Polymer treatment decreased the LL, PI, swelling index, and optimum moisture content of the soil and increased the compacted maximum dry density. Behavior of sulfate contaminated CL soil with and without treatment was quantified using a unique model that represented both linear and nonlinear responses. Also the model predictions were compared with published data in the literature.

Effect of nanocomposite on the strength parameters of soil

Subgrade soil stabilization is one of the primary and major processes in the construction of any highway. This paper evaluates the use of glass fibers in combination with nano-clay to improve the soil engineering properties. We intend to study the effect of adding nano-clay and glass fiber on soil mechanical properties, especially Shear parameters, using clayey soil with low liquid limit. The both ratios of glass fiber and nano-clay added to the soil are between 0.5% and 1.5%. Results of this study showed that nano glass fibers and nano-clay can be very effective in improving mechanical properties of clay. Adding nano particles in clay negatively affects the failure strain, but the increase in the glass fibers contents is connected with the increase in failure strain. Also, binary usage of fiber and nano- particles had a remarkable improvement appearing in clay strength than using the single type of fiber. It was found that a considerable shear strength increase up to 84% could be achieved depending on both the ratios of glass fiber and nano-clay that is used to improve the soil. In addition, the experiment results show that, binary usage of fiber and nano-clay can increase the unconfined compression strength of soil.