Interpretation of Cone Penetration Test Data of an Embankment for Coupled Numerical Modeling

The Nerang Broadbeach Roadway (NBR) embankment in Australia is founded on soft clay deposits. The embankment sections were preloaded and surcharged-preloaded to limit the post-construction deformation and to avoid stability failure. In this paper, we discuss the NBR embankment’s geology, geotechnical properties of the subsurface, and long-term field monitoring data from settlement plates and piezometers. We demonstrate a comparison of cone penetration test (CPT) and piezo cone dissipation test (CPT-u) interpreted geotechnical properties and the NBR embankment’s foundation stratification with laboratory and field measured data. We also developed two elasto-viscoplastic (EVP) models for long-term performance prediction of the NBR embankment. In this regard, we considered both the associated and the non-associated flow rule in the EVP model formulation to assess the flow rule effect of soft clay. We also compared EVP model predictions with the Modified Cam Clay (MCC) model to evaluate the effect of viscous behavior of natural Estuarine clay. Both EVP models require six parameters, and five of them are similar to the MCC model. We used the secondary compression index of clay in the EVP model formulations to include the viscous response of clay. We obtained numerical models’ parameters from laboratory tests and interpretation of CPT and CPTu data. We observed that the EVP models predicted well compared with the MCC model because of the inclusion of soft clay’s viscosity in the EVP models. Moreover, the flow rule effect in the embankment’s performance predictions was noticeable. The non-associated flow rule EVP model predicted the field monitoring settlement and pore pressure better compared to the MCC model and the associated flow EVP model.

Effects of controlled burn rice husk ash on geotechnical properties of the soil

Pozzolanic reactions of RHA entirely depends on controlled burning condition. The current study illustrates the effects of controlled burn rice husk ash (RHA) on the geotechnical properties of A-2-4 type soil. The compactibility, bearing capacity, compressive strength, and shear strength were investigated as the important geotechnical properties on soil with 0%, 5%, 10%, and 15% of RHA admixtures. Considering the 7-day moist curing, standard Proctor compaction tests, California Bearing Ratio (CBR) tests, Unconfined Compressive Strength (UCS) tests, Consolidated-Drained (CD) Triaxial Compression tests, and Scanning Electron Microscopy (SEM) tests were conducted on soil-RHA combinations. The test results showed that the optimum moisture content increased, but MDD reduced with the increment of RHA content. Soil with 5% RHA showed the increase of CBR (39.5%), UCS (6.0%), modulus of deformation (56.3%), cohesion (11.8%), and angle of internal friction (6.3%) compared to control specimen which indicated that the application of burnt RHA at a controlled temperature significantly enhanced the geotechnical properties of soil. SEM image on soil with 5% RHA also observed the best microstructural development.

Geotechnical Properties of Soft Marine Soil at Chan May Port, Vietnam

Soft marine soil deposit is distributed under the sea with many special properties. This type ofsoil is rarely researched in Vietnam because of the difficult geotechnical investigation under the sea level.In this paper, the experimental laboratories were performed to investigate the geotechnical properties ofsoft marine soil at Chan May port, Vietnam. The field investigation results indicate that the thickness ofsoft soil varies from a few meters to more than ten meters. Soft soil has a high value of water content,void ratio, and compressibility and a low value of shear strength. The compression index has a goodrelationship with water content, liquid limit, and dry unit weight. The unit weight, shear strength, and preconsolidationpressure increase with the increase of depth. These results show that the soil in the studyarea is unfavorable for construction activities.

Experimental Investigation on the Influence of Oven-Drying on the Geotechnical Properties of Volcanic Ash-Derived Residual Soils

For thousands of years, the volcanic activity present along the Andes Mountain range has generated a large amount of pyroclastic material. As a result, around 60 percent of the soils present in Chile have a volcanic origin, of which, we can find soils derived from volcanic ash. These correspond to soils whose origin is the weathering of volcanic ash, which generates minerals such as allophane, imogolite, and halloysite. The presence of these minerals gives these soils unique geotechnical properties, such as high plasticity, low dry unit weight, and a unique internal structure. Subjecting these soils to extreme temperatures like those needed to perform standard laboratory tests produces changes in their structures, and thus in their geotechnical behavior. These changes are important to be aware of with respect to slope stability problems, embankment conformation, surface foundations, etc. In the present study, a type of soil found in Chile originating from the weathering of volcanic ash and locally named Trumao was studied. Due to its age and formation processes, the main minerals found in the soil are allophane and imogolite, and hence it belongs to the allophanic soil type. The material was studied in its natural state (undisturbed) and, after being oven-dried using common geotechnical tests, the behaviors of both samples were compared. The study shows that some properties are affected significantly by the oven-drying process, and thus it is not recommended to expose the material to high temperatures during geotechnical laboratory testing to avoid misleading results.

Prior Assessment of Variability in the Geotechnical Properties of Soils for Efficient Infrastructure Management

Advance assessments of variations in geotechnical properties of soils are invaluable in making a crucial judgment of geotechnical engineering projects. It could drive to reduce the number of field and laboratory tests so that efficient management design and construction of infrastructure project outputs can be achieved. In this study, we aim at assessing the geotechnical properties of residual, alluvial, marshy, coastal, and compacted soils within the wet and the dry zones of Sri Lanka. Plastic limit (PL), liquid limit (LL), shrinkage limit (SL), plasticity index (PI), liquidity index (LI), compression index (Cc), swell potential (SP), activity, natural moisture content (NMC) and SPT-N values were either extracted from reports or deduced from formulas and graphs. Wet zone marshy soils (My_W) show highest statistical means for PL (~23%), LL (~40%), PI (~16 %), SL (~20 %), LI (~ 1%), Cc (~ 0.200) and NMC (~ 35%), indicating poor engineering properties. Wet zone residual soils (Re_W) represent a wide range of direct correlations to the parent material. CH, OH, CL and SM soil groups for some My_W show high expansive, while, CL, Pt/CL, OL, SC, SM in My_W, CL, and SC in Re_W and CL in Dry Zone Alluvial Soils (Al_D) display medium expansive. The higher SPT-N values were recorded in the upper 6.00m and between 12.00-16.00m for the shell of earth dams (SED_D) in the dry zone, in contrast to Al_D soils representing higher N values for 6.00-12.00m. Except for marshy soils, no vertical variation for plasticity was observed in others. Since high to medium swell potential in the unsaturated zone is encountered within the upper 1.50m, attention should pay to the My_W. LL and PI of My_W were strongly correlated (R2 = 0.83) so that an equation PI% = -1.91 + (0.46*LL%) could be used to calculate PI. The results provide baseline geotechnical property variations for the five soils in Sri Lanka so that during planning, best-calculated assessment could be achieved which could minimize time and cost for crucial geotechnical investigations.

A Comparative Study on the Effect of Class C and Class F Fly Ashes on Geotechnical Properties of High-Plasticity Clay

Clays generally have a low strength and capacity, and additives are usually used to stabilize them. In recent years, using fly ash to stabilize soil has decreased environmental pollution while also having an economic benefit. The objective of this study is to perform a comparative investigation on the effect of class C and class F fly ashes on geotechnical properties of high-plasticity clay using the Atterberg’s limit, compaction, California Bearing Ratio (CBR), and unconfined compressive strength tests. The results showed that with an increase in the amount of fly ash, there was a decrease in the maximum dry density and an increase in the optimum moisture content. Moreover, an addition of fly ashes of up to 25% caused a reduction of the liquid limit and plasticity index, and an increase in the maximum unconfined compressive strength and CBR. Lengthening the curing time had a positive impact on the unconfined compressive strength of the soil. The soil samples with class C fly ash were seen to possess more efficient geotechnical properties as compared to class F fly ash.