Field Vane Shear Tests Research Articles

Undrained Shear Strength from Field Vane Shear Test (VST) of Soil at Shoreline Area

The effect of soil shear strength at the shoreline area is the focus of this study. Pantai Punggur, Batu Pahat, Johor, has been chosen as the subject location for the soil shear strength investigation. It is located on the west coast of Johor, with latitudes ranging from 1.62° to 1.87° N and longitudes ranging from 102.78° to 103.19° E. The purpose of this study is to use a field vane shear test (VST) to determine the undrained shear strength of shoreline areas. Soil samples were collected at specific locations known as Zones A, B, C, D, and E, and data for sediment shear strength was obtained from field vane shear test (VST) methods. From the undrained shear strength test at 0.5 m depth at high tide (HT) and medium tide (MT) data for December 2021, Zone A had a Cu reading of more than 4.5 kPa, followed by Zones B, C, and D, and lowest at Zone E. Next, in the December 2021 data at the HT level, Zone A has a Cu reading greater than 4.5 kPa at 0.5 m and 1.0 m, while other Zones have readings less than 3.0 kPa. It can be concluded that the depth of a part also influences the data in this study. When the depth increases, the shear strength of the data also increases. This study will serve as a benchmark for future conservation efforts. Based on the findings, more effective control measures for preserving and conserving coastal areas may be developed.

Evaluating the Undrained Shear Strength of Kalimati Soil Using Field Vane and Unconfined Compression Test; a Study on Applicability of Bjerrum’s Correction Factor

Rapid urbanization and geological challenges in Kathmandu have made it crucial to understand the geotechnical properties of the soil in the region. This study here focuses on the undrained shear strength of silty clay in Kalimati, Kathmandu, and investigates the applicability of Vane Shear tests and its parameters over other shear strength tests from other methods. Geotechnical investigations were carried out at three locations within the Kathmandu Engineering College premises and in-situ and laboratory tests were conducted on undisturbed and disturbed samples. Then the study compared the field vane shear strength, undrained strength from unconfined compression tests, and laboratory vane shear strength of the samples. For the field vane shear test the correction factor as suggested by Bjerrum was used and the results indicate that this method overestimates the shear strength in Kalimati soil, indicating no adjustment is necessary. The findings of this study have important implications for the design and construction of structures in the region, and contribute to a better understanding of the geotechnical properties of Kathmandu soil.

Mitigation of lateral slope movement and soil improvement using the vacuum-PVD scheme

This paper interprets the results from field monitoring which was carried out during vacuum-PVD improvement in a site located near an actively moving slope. Interestingly, the monitoring results showed, among other things, mitigation in the outward lateral movements during and after the preloading process indicating relative stability in the slope and the efficiency of vacuum to mitigate lateral movements during the preloading period. Analyses were made on other field parameters such as pore pressure and settlement, as well as back-calculation of flow parameters to be considered during vacuum preloading design, such as permeability ratio (kh/ks) and horizontal consolidation coefficient (Ch) due to vacuum-PVD, were carried out. Post improvement, appropriate geotechnical properties were obtained from laboratory tests of clay specimens from borehole samples and undrained shear strengths were measured from unconfined compression and field vane shear test. The obtained properties indicated improvement in soft soil properties with a reduction in water content and an increase in maximum past pressure, OCR and undrained shear strengths. The prediction made for final shear strength using past literature, where applied additional incremental stress was reduced with depth, matched well with the shear strengths recorded from field testing.

Observations from Ground Improvement Using Vacuum Consolidation Method

In the modern world of Civil Engineering, challenges arise during the various phases of construction, starting from the project development phase to the completion of the project. One of the main factors to be considered before commencing any infrastructure project is the foundation of where it is to be built. Without a strong foundation, it's not possible to proceed further to subsequent stages and in some cases, significant improvements may be required before starting the construction process. Although there are several different available methods for soil improvement in Civil Engineering, preloading using vacuum pressure with prefabricated vertical drains (Vacuum Consolidation Method) is one of the commonly applied techniques. Nowadays, it is widely used in countries having soft soil settlement problems. This paper presents the observations made from a soil improvement project using VCM including the site conditions and methodologies adopted during the process. The field data related to parameters such as pore pressure, settlement and shear strength improvement in natural soft clay have been presented and discussed. The degree of consolidation in the field has been back-calculated from settlement data and compared with values obtained from the 1-D consolidation equation. Field investigation tests, such as borehole tests and field vane shear tests, were performed before and after the soil improvement and it was found that the soft soil properties can be enhanced using vacuum consolidation without the use of any surcharge loading as well.

Measuring Seismic Shear Strengths for Bootlegger Cove Clay

This article presents an evaluation of the undrained shear strengths for Bootlegger Cove Clay (BCC) in the Anchorage, Alaska area for seismic stability and permanent deformation analyses for public and private infrastructure. Given the high seismicity of the area, the focus herein is on measuring and selecting undrained strengths that reflect the effects of cyclic loadings and level of permanent displacement predicted to occur. The laboratory cyclic test results herein show that BCC will mobilize at least 80 % of the static peak undrained shear strength (∼20 % reduction) if field permanent displacements are less than 0.1 m. If field displacements are between 0.1 and 1.0 m, BCC will mobilize an undrained shear strength in between the static peak and residual undrained strengths in addition to the 20 % reduction for the effects of cyclic loading. If field permanent displacements are greater than 1.0 m, the BCC will mobilize the static residual undrained strength. Recommendations for field vane shear and laboratory shear tests are presented for measuring these undrained shear strengths.

Reclamation and Ground Improvement of Soft Marine Clay for Development of Offshore Terminal 4, JNPT, Navi Mumbai

A container yard of around 100 Ha area was developed as part of the fourth terminal for Jawaharlal Nehru Port Trust (JNPT) in Navi Mumbai by means of reclamation in sea over soft, compressible marine clay. Ground improvement of the subsoil was warranted in order that the finished reclamation satisfies the stringent serviceability criteria. Extensive offshore geotechnical investigation campaign comprised conventional borehole sampling, laboratory tests and various in situ field tests such as CPTu, field vane shear tests, etc. Investigations revealed clay thicknesses of 4 m–22 m, with top layer showing undrained shear strengths less than 7 kPa and increasing with depth, underlain by weathered basalt. The ground was improved using prefabricated vertical drains (PVDs) with preloading. Radial consolidation and cone dissipation tests were carried out to establish the coefficient of horizontal consolidation (ch). The marine reclamation is confined on all sides by a perimeter bund with revetment, Stability analyses carried out for this bund showed that it was necessary to have overfill beyond the reclamation cope line along with tension geotextiles so as to achieve the prescribed factors of safety against slope failure. After removal of the preloading, the overfill was cut back to the final geometry and revetment was provided along the perimeter. Extensive geotechnical instrumentation and monitoring were conducted using multilevel magnetic extensometers, settlement gauges, inclinometer and piezometers to monitor the behaviour and performance of ground improvement. Field ch and smear coefficients were back-calculated. Around 200 confirmatory boreholes (CBH) were carried out after completion of ground improvement to ascertain the post-improvement and validate the design parameters, thus eliminating the risk of post-construction settlement.

Research on Field vane Shear Strength of Marsh Peat Soil in South America

According to high backfilling project in South America, through a large number of laboratory tests data and field vane shear test results, the engineering characteristics of marsh peat soil in this area are analyzed, and the variation of the shear strength of the peat soil along the depth and the sedimentary characteristics are demonstrated. The selection principle of the calculation index of the foundation for the high-filling operation of peat soil foundation is proposed. It has reference significance for similar engineering construction.

Design and Fabrication of a Low Cost Field Vane Shear Apparatus

The un-drained shear strength of soil is of great concern in many geotechnical engineering applications. The vane shear test is a simple, easy and popular type of in-situ shear test to the geotechnical engineers and geologists. However, it is not fairly appreciated by the academic personnel or field engineers as compared to the other shear strength test of soil. There are different types of field vane shear test apparatus existing in the market, but most of them are costly and have limited measuring capacity. The main objective of the research work was to develop a low cost field vane shear apparatus with higher measurement capacity using local materials and accessories. In this research work, a simple manually operated field vane shear apparatus was designed and fabricated. Four vane blades were welded to the vane shaft and a socket was added at the top. The most important component of the design apparatus is the torque wrench which is used to determine the torque both in clock and anti-clock wise direction. The torque value is then converted into the shear strength. The designed apparatus is suitable to determine the un-drained shear strength of soft to stiff clay soil up to 300 kPa. The performance of the device was tested directly in the crop field near Kumargaon area at Sylhet city. Average shear strength from in-situ test was found 49 kPa for medium to stiff clay. For the assessment of accuracy of the designed apparatus, undisturbed soil sample was collected from the same location of the field and then tested by laboratory vane apparatus according to ASTM D4648 and fairly similar result was observed. The instrument’s output repeatability was checked from the test data and the values were found quite satisfactory with a range of 2.68 to 5.87. The designed apparatus are about five times cheaper than the conventional apparatus available in the market.

Self-boring in situ shear pressuremeter testing of clay from Dalian Bay, China

A new geotechnical in situ test technique using a self-boring in situ shear pressuremeter (SBISP) is developed to evaluate the initial state (horizontal at rest pressure Ph), deformation (yield pressure Pf and pressuremeter modulus EP) and strength characteristics (cohesion C and internal friction angle φ) of soil. The SBISP possesses a self-boring drilling functionality that can greatly reduce the disturbance of the tested soil. The multistage compound loading method, which applies normal stress incrementally to the soil in the test hole while repeatedly applying shear stress, was adopted.Relying on the investigation of the cross-sea traffic engineering of Dalian Bay, three sites in the sea area of Dalian Bay were selected for SBISP testing of clay. The field vane shear test (FVT), pressuremeter test (PMT) and unconsolidated-undrained triaxial compression test (UU) were also evaluated at each testing site to compare with the SBISP test. The results measured by the SBISP and comparative tests (FVT, PMT and UU) showed the same trends with an increase in depth and change in strata. The differences in the test results were discussed in terms of the disturbance effect, anisotropy of undrained shear strength, differences in loading methods and instrumentation used in the different tests. A comparison between the results measured by the SBISP and in comparative tests shows that the engineering characteristics of Dalian Bay clay evaluated by SBISP are fairly accurate and can provide reference for the investigation and design of the cross-sea traffic engineering of Dalian Bay.

Modelling of spatial variability of soil undrained shear strength by conditional random fields for slope reliability analysis

• A simplified approach for generating conditional random field is proposed. • Analytical posterior statistics can be derived using the proposed approach. • The proposed approach is more efficient and accurate than adaptive Bayesian updating with structural reliability methods. • The actual spatial variation can be well characterized by conditional random field. • Borehole layout scheme affects the probability of slope failure significantly. Conditional random field model can make best use of limited site investigation data to properly characterize the spatial variation of soil properties. This paper aims to propose a simplified approach for generating conditional random fields of soil undrained shear strength. A numerical method is adopted to validate the effectiveness of the proposed approach. With the proposed approach, the analytical posterior statistics of spatially varying undrained shear strength conditioned on the known values at measurement locations can be obtained. The conditional random field model of undrained shear strength is constructed using the field vane shear test data at a site of the west side highway in New York and the probability of slope failure is estimated by subset simulation. A clay slope under undrained conditions is investigated as an example to illustrate the proposed approach. The effects of borehole location and borehole layout scheme on the slope reliability are addressed. The results indicate that the proposed approach not only can well incorporate the limited site investigation data into modelling of the actual spatial variation of soil parameters by conditional random fields, but also can capture the depth-dependent nature of soil properties. The realizations of conditional random fields generated by the proposed approach can be well constrained to the site investigation data.

Failure Investigation at a Collapsed Deep Open Cut Slope Excavation in Soft Clay

Collapse of a 7.08-m-deep open cut excavation for the bank of a navigation lock in sensitive soft clay in Zhejiang, China, is presented in this paper. Cone penetration tests, field vane shear tests (VSTs), and traditional laboratory tests have been performed to investigate the soil properties after the collapse. According to the test results, the soft soil layers of mucky clay and muck have been found to be disturbed because of the effects of the boring holes. For bored concrete piles, the stresses release due to the cut slope, thus its shear strength is much lower than that measured from laboratory tests. The shear strength reduction technique based on a finite-element method program has been used to study the excavation behavior and overall factor of safety (FOS) of the excavated slope considering geometries of original design, later adopted schemes and soil properties associated with various test types. The computed FOS values obtained from VST results are lower than the corresponding recommended values and just a little higher than the limited value. Thus the excavated slope may easily collapse triggered by additional vehicles and surface surcharge loads. The reasons of excavation collapse can be explained as the misuse of soil properties for designers, and inadequate construction process management. The investigation of the failure provides experiences and lessons for the design and construction of similar projects in sensitive soft clay.

Correlation of JKR Probe with Undrained Shear Strength

The JKR probe test is a popular field test in Malaysia, and is especially used in soft soil areas to determine bearing capacity. However the correlation of undrained shear strength (Su) and the JKR probe test is not available at this moment. This study was performed to develop an empirical correlation of JKR probe and undrained shear strength of soft to stiff soil. In order to produce the correlation, the JKR probe test and the vane shear test have been performed at Universiti Tun Hussein Onn Malaysia (UTHM). Six JKR probe tests and 12 field vane shear tests were performed in close proximity to obtain good correlation. The results show that undrained shear strength and JKR probe can be correlated as Su=18J0.3. The proposed correlations will serve as a reference for engineers in estimating undrained shear strength, especially in low-risk construction design.

Mineralogy and Geotechnical Properties of Ultrasoft Soil from a Nearshore Mine Tailings Sedimentation Pond

An engineering geological study was undertaken to determine the engineering properties, and mineralogy of ultrasoft soils (USS) obtained from a nearshore mine tailings sedimentation pond. The USS is a high plasticity clay of high water content and low shear strength. Marine bathymetric and seismic reflection surveys were undertaken in the sedimentation pond located in the foreshore of the Eastern part of the Republic of Singapore. Specimens collected from the bore holes were tested to determine the engineering and mineralogy properties of the USS. Field vane shear tests were undertaken just adjacent to the sampling bore holes to determine the shear strength properties of the USS. The mineralogical properties of the USS were determined using X-ray diffraction and scanning electron microscope techniques. The USS is under consolidated soil where higher density and lower water content were found at deeper depth. The USS had three different compression indices under three log cycles of effective stress between 1–10, 10–100, and 100–1,000 kPa. This is the main characteristic of USS, which diverts from reconstituted soil. The outcome of this research is fundamental for understanding the compression behavior and subsequently the development of a constitutive model for USS, typical found in sedimentary pond.

Mineralogy and geotechnical properties of Singapore marine clay at Changi

An engineering geological study was undertaken to determine the geotechnical properties and mineralogy of Singapore marine clay at Changi in the Republic of Singapore. This soft soil is a quartenary deposit that lies within submarine valleys cut in an old alluvium formation. The marine clay comprises a soft upper marine clay layer overlying a stiffer lower marine clay layer. An intermediate stiff clay layer is sandwiched between these two marine clay layers; it is believed to be the dessicated crust of the lower marine clay layer. In the present study, morphological and mineralogical observations of Singapore clay were taken by scanning electron microscopy, X-ray diffraction and photographic identification. The geotechnical investigation included physical, compression, permeability and field vane shear tests. The upper marine clay was found to be soft with undrained shear strength values ranging from 10 to 30kPa, while the lower marine clay was found to have undrained shear strength values from 30 to 60kPa. The sensitivity of the marine clay at Changi varied from 3 to 8 and is described as highly sensitive marine clay. The upper clay layer had a coefficient of consolidation of 0.47–0.6m2/year due to the vertical flow (cv) and a coefficient of consolidation of 2–3m2/year due to the horizontal flow (ch). The lower marine clay had a cv of 0.8–1.5m2/year and a ch of 3–5m2/year, while the intermediate stiff clay had a cv of 1–4.5m2/year and a ch of 5–10m2/year. The primary clay mineral was kaolinite, followed by smectite and mica. With this high kaolinite content, the activity of the Singapore marine clay was found to be low at approximately 0.5–1.3 and classified as inactive to active clay. With reference to the intrinsic state line, natural Singapore clay (upper, intermediate and lower layers) has been classified as structured clay and is in a meta-stable state. The compression behaviour can be modelled by the Intrinsic State Line and the destructuring framework. The predicted and the measured compression curves were comparable for various depths. The successful modelling of compression curves will be useful for settlement calculations and for further research on the development of a constitutive model for Singapore marine clay.

Study on relationship between static cone penetration strength and shear strength of soil

On basis of the analysis on results of laboratory test, the field vane shear test and the static cone penetration test of different types of soil in Tianjin, it is proposed that there is significant positive linear correlation between the static cone penetration tip resistance and the vane shear strength. Moreover, for clay a more distinct linear correlation exists than that for mucky soil and silty clay. Therefore the results of static cone penetration test can be applied to the stability calculation.

Failure Investigation at a Collapsed Deep Excavation in Very Sensitive Organic Soft Clay

Collapse of a 15.7-m-deep excavation in very sensitive organic soft clay in Hangzhou, China, is presented in this paper. The collapse of the excavation caused the break and/or inclination of the retaining walls, the wracking of the supporting system, significant sinking of a major road adjacent to the excavation site, and also the break in a water main beneath the road. After the collapse, the ground disturbance due to the collapse was investigated by cone penetration tests (CPTs) and field vane shear tests (VSTs). A simplified method, based on the CPT and VST test results, was used to evaluate the strength reduction ratio (SRR) of the in situ soils. According to the SRR values of the soils at different depths, the lower boundaries of the severely disturbed soils were determined and a possible slip failure surface passing through the bottom of the severely disturbed soils was justified. The factors of safety (FOSs) against basal heave of the excavation calculated from various methods were 1.05, 0.74 and 0.89, respectively. These computed values were much smaller than the corresponding recommended values. The stability number N of the excavation was calculated to be 7.4. The overall FOS was studied using the shear strength reduction technique based on a finite-element method (FEM) program. The FEM analysis results indicated that the FOS of the excavation was 0.97, and the computed slip failure surface fit well with that from the soil disturbance investigation. The failure mechanism of the excavation was then justified to be a basal heave. The main reasons leading to the collapse and lessons learned from the collapse are discussed. The investigation of the failure provides experiences and lessons for deep excavation design in very sensitive organic soft clay.

Evaluation of I-wall in New Orleans with back-calculated total stress soil parameters

This study back-calculated moduli and shear strength of soils in London Canal Ave., New Orleans, using full-scale load test data, and re-evaluated the behavior of the I-wall to explore how the existing levees and floodwalls may be reliably retrofitted and future levees and floodwalls may be designed. From the back-calculation, it turned out that the moduli of the field soils were mostly higher (1–12 times) than magnitudes appeared in Interagency Performance Evaluation Task Force (IPET). But the shear strength of a water-glazed Marsh layer in the gap turned out to be substantially lower (0.2–0.25 times) than the magnitude appeared in IPET. This much strength reduction was confirmed by field vane shear tests: tests with artificial water infiltration into the field vane hole presented immeasurably low disturbed strength and resulted in very high sensitivity that might contributed to the failure. This study also shows that the gap development and strength reduction in the water-glazed Marsh layer are two main causes of levee failure, which have been predicted in previous research. The stiffer-than-expected moduli of underlain layers did not affect the failure mechanism of the levee substantially because these underlain layers remained elastic. Therefore, retrofitting solutions should be the ones that may prevent the gap development and to reinforce the Marsh layer.

Characterization of thick varved-clayey-silt deposits along the Delaware River by field and laboratory tests

The existence of thick compressible varved clayey silt deposits along the Delaware River presents one major obstacle for design and construction of structures or industrial facilities in this region. To understand the characteristics of this thick weak soil layer and then develop reliable soil parameters for future earthwork design and construction, a comprehensive soil testing program was carried out. The program consisted of both in situ tests [e.g., standard penetration test borings, piezocone penetration test (CPT) soundings, Marchetti flat dilatometer test soundings, seismic shear wave test soundings, CPT pore pressure dissipation tests, and field vane shear tests] and laboratory tests (e.g., soil index tests, consolidation tests, triaxial tests, and chemical tests). Additionally, a field surcharge test program with and without installation of wick drains was carried out to investigate the compressibility of the thick clayey silt deposit and the efficiency of wick drains to help accelerate consolidation. The field and laboratory test results showed that the varved clayey silt deposit was normally consolidated to slightly overconsolidated and moderately to highly compressible. Its physical properties were intermediate between those of Savannah muddy clay and Shanghai soft clay, while much closer to that of Shanghai soft clay. Due to its lamination structure in the horizontal direction, the horizontal consolidation coefficient of the varved clayey silts was significantly greater than that in the vertical direction. The measured undrained shear strength of the varved clay silt almost increased linearly with depth. The installation of wick drains in the thick clayey silt deposits accelerated primary consolidation, but showed no effect on the secondary consolidation under constant loading. The findings obtained from this study will be beneficial for future design and construction of earthworks along the Delaware River.

Evaluation of the undrained shear strength of Busan clay

The current paper presents an estimation of the undrained shear strength (su) of Busan clay through a comparison of the results of field vane and laboratory shear test results at two sites in the Nakdong River Delta. The results indicate that because of fabric effects in the clay, determining the effective overburden stress (σν0′) and the field vane strength (su,FV) based on the corrected cone resistance (qt) is effective. The ratio su,FV/σν0′ varied with the depositional units, independent of the plasticity index (Ip). In comparison to su,FV, combined shear strengths obtained from the consolidated-undrained compression and extension triaxial tests were slightly smaller and occasionally scattered because of the effects of sample disturbance. The laboratory shear strengths rely on the strain rate, regardless of the Ip. The correction factors using two different approaches were larger than those of the existing methods. For practical applications, the qt-based corrected vane strengths with the correction factor (µ) are thus recommended as the mobilized undrained shear strength of the clay (i.e., µsu,FV/ σν0′ of 0.23), which is similar to the corrected value of the combined shear strengths for all depths.

Ground Investigations for Changi East Reclamation Projects

Geotechnical ground investigation is important in all construction works particularly, land reclamation projects. The Changi East reclamation project is a mega project that involves creation of land space as large as 3,000 hectares in multiple phases between 1991 and 2005. Ground investigation plays a critical role in the Changi project which involved substantial amount of ground improvement works after reclamation by sand filling. One important aspect of the investigation was to evaluate the geotechnical characteristics of the underlying compressible soils beneath the original seabed for the selection of suitable methods of ground improvement. The other important aspect of the investigation was to characterize and verify the compactness of the reclaimed sand fill. Many types of in situ tests were extensively used in the project. The field vane shear test provides correlations between the undrained shear strength and depth for the upper and the lower marine clay strata in the Northern part and the Southern Part of the reclaimed site. Combined with laboratory undrained shear strength tests, the field vane strength profiles allow the derivation of the undrained shear strength over effective stress ratios for the upper and the lower marine clays. In addition, results from three other in situ tests, the piezocone cone penetration test, the flat dilatometer test, and the self boring pressuremeter test provided useful verification of these correlations. A field-performance based method of assessing degree of consolidation in the underlying clay was developed by combining field monitoring, laboratory testing and conventional as well as specialized in situ testing. An effective use of in situ testing methods for assessment, the outcome of ground improvement and for fill quality control in the densification of granular soils is illustrated with field observation data collected at the project site.