Vertical Coefficient Of Consolidation Research Articles

Research on experimental evaluation horizontal coefficient of consolidation Ch on CPTu dissipation test to determine permeability parameters in the field to improvement of soil soft.

In the solution of soft soil improvement by preloading method combined with prefabricated, the horizontal consolidation coefficient Ch is a very important parameter to help predict the settlement speed of soft soil. But when designing the coefficient of horizontal consolidation, it is often assumed that the coefficient of vertical consolidation is quite large. This can lead to settlement over time that will fluctuate in a rather large range of values. In this paper, research and evaluation of the horizontal consolidation coefficient Ch by dissipation test on piezocone penetration device with pore water pressure measurement has been mentioned to determine the permeability parameters in-situ for the soft soil improvement at the projects.

Study of Anisotropy Characteristics of Bogor Volcanic Soil

Anisotropy in soil results from the deposition process which describes the characteristics of the soil grains or is caused by stress or from the consequences of stresses caused during deposition and subsequent erosion. All soils behave in general anisotropy and some exhibit undrained shear strength. This study conducted 2 tests, namely the first field testing with original soil samples in the form of CPTu and dilatometer. The CPTu test's objective is to determine the vertical soil parameters, while the dilatometer is to determine the horizontal soil parameters. This study indicates that the indication of anisotropy in all shear strength tests is evident in the results of the CPTu test and the Dilatometer test. TX - UU and consolidation show that the horizontal shear strength (Suh) is greater than the vertical slope shear strength (Suv). In this case, the ratio obtained for shear strength is Suh = 1.3 Suv. And from the results of the consolidation test in the laboratory, it was found that the horizontal compression index parameter (Cc horizontal) was greater than the vertical (Cc vertical) and the horizontal coefficient of consolidation (Ch) is greater than the vertical coefficient of consolidation (Cv).

Research on Horizontal Coefficient of Consolidation of Vietnam’s Soft Soil

The horizontal coefficient of consolidation is the most important parameter for designing the improvement of soil soft by prefabricated vertical drains (PVDs) combined with surcharge and vacuum preloading. This paper presents the experimental study on the horizontal coefficient of consolidation (ch) of some soft soils distributed in Vietnam. Thechvalue was determined by the laboratory test and CPTu dissipation test. The laboratory tests included the Rowe consolidation cell test and constant rate of strain consolidation with radial drainage test. Two types of consolidation laboratory tests were performed. The experimental results indicated that thechvalue is always larger than the vertical coefficient of consolidation of soil (cv). The ratio ofch/cvdepends on the consolidated pressure, type of soil, and the anisotropy of soil. The ratio ofch/cvis different in different types of soft soil in Vietnam. In the normally consolidated state, thech/cvratio ranges from 1.35 to 10.59. It was necessary to choose thechvalue at the consolidated stress level for calculating the PVD spacing.

Development of analytical models to estimate the increase in pile capacity with time (pile setup) from soil properties

This paper presents the analyses of twelve prestressed concrete (PSC) instrumented test piles that were driven in different bridge construction projects of Louisiana in order to develop analytical models to estimate the increase in pile capacity with time or pile setup. The twelve test piles were driven mainly in cohesive soils. Detailed soil characterizations including laboratory and in situ tests were conducted to determine the different soil properties. The test piles were instrumented with vibrating wire strain gauges, piezometers, pressure cells that were monitored during the whole testing period. Several static load tests (SLTs) and dynamic load tests were conducted on each test pile at different times after end of driving (EOD) to quantify the magnitude and rate of setup. Measurements of load tests confirmed that pile capacity increases almost linearly with the logarithm of time elapsed after EOD. Case pile wave analysis program was performed on the restrikes data and was used along with the load distribution plots from the SLTs to evaluate the increase in skin friction capacity of individual soil layers along the length of the piles. The logarithmic linear setup parameter “A” for unit skin friction was calculated of the 70 individual clayey soil layers and was correlated with different soil properties such as undrained shear strength (Su), plasticity index, vertical coefficient of consolidation (cv), over consolidation ratio and sensitivity (St). Nonlinear multivariable regression analyses were performed, and three different empirical models are proposed to predict the pile setup parameter “A” as a function of soil properties. For verification, the subsurface soil conditions and setup information for additional 18 PSC piles collected from local database were used to compare the measured versus predicted “A” parameters from the proposed models, which showed good agreement.

Settlements and Consolidation Rates under Embankments in a Soft Soil with Vertical Drains

In this paper, a study was carried out in order to estimate settlements and consolidation rates under embankments constructed on Moroccan soft soils. Settlement measurements in several embankments in High Speed Railway project between two Moroccan cities, Tangier and Assilah, were analyzed. The objective of this study is to estimate settlement values and settlement rates, with sufficient precision, in soft soils under embankment loadings. It was found that the elastic method using the pressuremeter modulus results in more accurate settlement values than the oedometric method. Furthermore, settlement rates could be determined with fair accuracy by using a correlation between the vertical coefficient of consolidation and the liquid limit, and also by considering an isotropic behavior of soil.

Geotechnical Evaluation of Clayey Soil Contaminated with Industrial Wastewater

Abstract The impacts of industrial wastewater contamination on the geotechnical properties of clayey soil have been studied in the research presented in this paper. The contaminant in question is industrial wastewater released from Thi-Qar oil refinery as a by-product of production, and the soil samples obtained from Thi-Qar oil refinery plant in Al-Nassyriah (a city located in the south of Iraq). The geotechnical properties of contaminated soil samples were compared with those of intact soil to measure the effects of such a contaminant. The soil samples were obtained from three locations in the study area; representing the highly contaminated area, the slightly contaminated area, and the intact area used as a reference for comparison of test results. The results of the tests showed that the contaminant causes an increase of natural moisture content, field unit weight, Atterberg’s limits, and maximum dry unit weight, as well as an increase of the compression index and the coefficient of vertical consolidation. Also, the contaminant causes a decrease in specific gravity, the optimum moisture content initial void ratio, the swelling index, the coefficient of permeability, and cohesion between soil particles.

Development of Analytical Models to Estimate Pile Setup in Cohesive Soils Based on FE Numerical Analyses

This paper presents the numerical simulation of pile installation and the subsequent increase in the pile capacity over time (or setup) after installation that was performed using the finite element software Abaqus. In the first part, pile installation and the following load tests were simulated numerically using the volumetric cavity expansion concept. The anisotropic modified Cam-Clay and Dracker–Prager models were adopted in the FE model to describe the behavior of the clayey and sandy soils, respectively. The proposed FE model proposed was successfully validated through simulating two full-scale instrumented driven pile case studies. In the second part, over 100 different actual properties of individual soil layers distracted from literature were used in the finite element analysis to conduct parametric study and to evaluate the effect of different soil properties on the pile setup behavior. The setup factor A was targeted here to describe the pile setup as a function of time after the end of driving. The selected soil properties in this study to evaluate the setup factor A include: soil plasticity index (PI), undrained shear strength (Su), vertical coefficient of consolidation (Cv), sensitivity ratio (Sr), and over-consolidation ratio (OCR). The predicted setup factor showed direct proportion with the PI and Sr and inverse relation with Su, Cv and OCR. These soil properties were selected as independent variables, and nonlinear multivariable regression analysis was performed using Gauss–Newton algorithm to develop appropriate regression models for A. Best models were selected among all based on level of errors of prediction, which were validated with additional nineteen different site information available in the literature. The results indicated that the developed model is able to predict the setup behavior for individual cohesive soil layers, especially for values of setup factor greater than 0.10, which is the most expectable case in nature.

Geotechnical Investigations at the Dalian Offshore Airport, China

Based on the geotechnical investigation data of artificial island at Dalian Offshore Airport, the spatial distribution of the physical and mechanical properties of deposit soils was statistically analyzed. The field investigation revealed that the deposit soils could be subdivided into three strata, i.e., the top marine deposit stratum, middle marine-continental deposit stratum, and deep continental deposit stratum. Field and laboratory test results demonstrated that the marine deposit soils had high water content (31.2% < wn < 63.10%), large void ratio (0.88 < e0 < 1.75), low permeability (kv < 10−6 cm/s), flow-plastic state (IL > 1), under consolidated (OCR < 1), high compressibility (Es < 4 MPa), low shear strength (11.7 kPa < cu < 43.7 kPa), and low bearing capacity (0 < fak < 120 kPa), they could not be used as natural foundation. The marine-continental and continental deposits were normally consolidated to over-consolidated (OCR ≥ 1), medium compressibility (4 MPa < Es < 20 MPa), high shear strength (29.7 kPa < cu < 73.7 kPa), and high bearing capacity (fak > 120 kPa). In addition, regression analysis results showed that the compression ratio was positively correlated with the natural water content, the coefficient of vertical consolidation was negatively correlated with the plasticity index, and the coefficient of vertical permeability was positively correlated with the initial void ratio. The results of the field and laboratory tests were synthesized to provide a basis for reclamation design.

Consolidation Analysis by the Extended Taylor Method ( ETM ).

The Taylor t method is extended for improving the estimation of the end-of-primary (EOP) settlement p  and coefficient of vertical consolidation v c . The extended Taylor method (ETM) utilizes the same graphical procedure of the conventional Taylor method, but this procedure is repeated twice at any two U values greater than 52.6% instead of the one used in the Taylor method at 90%; U is the average degree of consolidation. The ETM explicitly relates v c to the slope of the initial linear portion of the t  - t curve as well as the EOP settlement p  ; t  is the settlement at time t during consolidation. The ETM can be applied with a minimum of four consolidation data points for estimating p  and v c . Two types of EOP settlements are distinguished; firstly, local EOP settlement pi  obtained by matching experimental results to theory at a particular U value; secondly, global EOP settlement p  obtained by extrapolation using two or more local EOP settlements. The ETM explains the observed differences in v c values estimated by the existing methods in terms of the differences in p  values obtained by these existing methods. Experimental results are used to validate and compare the extended Taylor method with the existing methods.

Consolidation Characteristics at the Constant Rate of Strain(CRS) Test

This study was carried out to investigate the consolidation characteristics of the remolded clay by the oedometer and the constant rate of strain(CRS) consolidation tests. As the rate of strain increases, the settlement rapidly decreased. As the ratio of the sand in the specimen increases, its effect on the rate of strain to the settlement was reduced. As the effective stress increased, the void ratio decreased, while the rate of strain increased, it did not show a clear variation. The reduction of the void ratio was shown to be less than the oedometer test. The coefficient of vertical consolidation with effective stress showed very large variation around preconsolidation stress, but the rate of strain did not provide significant effects. The rate of strain with effective stress gradually decreased at all tests and mixed ratio of sand. The rate of strain at the constant rate of strain tests showed smaller than in the oedometer test. The coefficient of consolidation at the constant rate of strain tests showed much more increase than in the oedometer test. The ratio of the vertical coefficient of consolidation by the odometer and the constant rate of strain tests showed a large difference according to various tests method and mixing ratio. Therefore, it is recommended that careful attention should be paid to designing the soft ground improvement.

Determination of Coefficient of Radial Consolidation Using Steepest Tangent Fitting Method

Barron (Trans ASCE 113:718–724, 1948) theoretical relationship between degree of consolidation (U r ) and time factor (T r ) is generally used to determine the coefficient of radial consolidation c r . Several researchers have proposed different laboratory techniques for obtaining the value of c r . However, the usual approach is to compare some salient features of the theoretical U r –T r relationship with the compression, δ and time, t based on the laboratory data. In this paper, rapid consolidation test procedure originally proposed by Su (J Soil Mech Found Div Am Soc Civ Eng No. 95: Proc. Pap. 1729 (1–9), 1958) to determine the coefficient of vertical consolidation (c v ) is extended to evaluate Barron’s coefficient of radial consolidation c r for the case of equal strain. The characteristic feature of the proposed method is the identification of the steepest tangent from the δ–log t plot. The slope of steepest tangent is independent of the drain spacing ratio (n) with a value of 0.847. This approach is rapid, and it predicts more reliable values of c r as it is less influenced by the secondary compression. In addition, this method is more versatile and can be applied for consolidation trends which do not always exhibit the typical S-shape.

Evaluating Deformation Modulus of Cohesive Soils from Piezocone Penetration Test for Consolidation Settlement

The piezocone penetration test (PCPT) interpretation methods were evaluated for reasonable prediction of the deformation constrained modulus (M), which is needed to calculate the consolidation settlement of cohesive soil. Seven sites in Louisiana were selected for this study. In each site, PCPT tests were performed, and soundings of cone tip resistance (qc), sleeve friction (fs), and pore pressures (u1 and u2) were recorded. Dissipation tests were conducted at prespecified penetration depths and used to estimate the vertical coefficient of consolidation (cv) using the Teh and Houlsby interpretation method. High-quality Shelby tube samples were collected close to the PCPT tests and used to carry out a laboratory testing program, including consolidated undrained triaxial tests and one-dimensional consolidation tests. The constrained modulus (M) values predicted by using the different interpretation methods were compared with the reference values determined from the laboratory consolidation tests. Results of this study showed that the Sanglerat method was able to predict Mbetter than the other methods. Two correlations were also developed to predict M from the corrected cone tip resistance (qt) and the net cone tip resistance (qt - σvo). The results of this study were verified by comparing the predicted total and time rate of settlements estimated from piezocone penetration and dissipation data with the laboratory-calculated and field-measured settlements for three selected sites.

Reliability of Piezocone Penetration Test Methods for Estimating the Coefficient of Consolidation of Cohesive Soils

The current piezocone penetration test (PCPT) interpretation methods were evaluated for their capability to estimate the vertical coefficient of consolidation (cv) of cohesive soils reasonably by using the piezocone dissipation tests. Seven PCPT methods were evaluated. Six sites in Louisiana were selected for this study. At each site, in situ PCPT tests were performed, and soundings of cone tip resistance, sleeve friction, and pore pressures at different locations were recorded. Piezocone dissipation tests also were conducted at different penetration depths. High-quality Shelby tube samples were collected close to the PCPT tests and were used to carry out a comprehensive laboratory testing program. The (cv) values predicted by the different interpretation methods were compared with the reference values determined from the oedometer laboratory tests. The results of this study showed that two methods can estimate cv better than the other prediction methods.