Characterization by Cone Penetration Tests of the decalcified Zandvliet Sand (Lillo Formation, North Belgium)

The sandy Zandvliet Member represents a particular, decalcified facies in the top of the Pliocene Lillo Formation in northern Belgium. Based on the correlation with nearby boreholes at the type locality of the Zandvliet Member, we were able to characterize this unit on Cone Penetration Tests. Compared to the underlying Merksem Member, the Zandvliet Member generally shows markedly lower cone resistance values. Since besides the decalcification, the Zandvliet Member is lithologically nearly identical to the underlying Merksem Member, the lower cone resistance values in the Zandvliet Member compared to the Merksem Member can only be the result of the decalcification of the Zandvliet Member. Indeed, the partly decalcified top of the Merksem Member also gives similar cone resistance values as the Zandvliet Member. Decalcification of the Eocene Brussel Sand in central Belgium is also known to have resulted in lower cone resistance values. Our Cone Penetration Test interpretations show that the thickness of the Zandvliet Member strongly varies across short distances (>10 m across 1 km). As the Zandvliet Member thickens, the underlying Merksem Member thins and vice versa. This trend is not in line with that of the under- and overlying strata, i.e. intraformational, nor with the depositional environment of these units. The thickness changes of the Zandvliet Member therefore purely reflect changes in depth of the post-depositional decalcification into the original shell-bearing sand (i.e. original Merksem Member). This confirms the existing hypothesis that the Zandvliet Member actually represents the decalcified part of the Merksem Member. The anomalous heavy mineralogy of the Zandvliet Member compared to the other members of the Lillo Formation cannot be readily explained by the acid chemical weathering which caused the decalcification. This may rather be related to a change in the primary heavy mineral signal of the upper part of the Merksem Member and equivalent Zandvliet Member compared to the underlying sequences of the Lillo Formation. The reason for the post-depositional decalcification could be similar to the Pleistocene changes in soil acidity invoked for decalcification of time-equivalent Red Crag sand in England.

Correlation between Electrical Resistivity and Cone Penetrometer Test Data for Geotechnical Site Investigation

The use of the electrical resistivity method provides cost-effective subsurface information faster and allows reliable interpolation to be made between the tested points. It is therefore desirable to generate consistent data from resistivity measurements by using empirical relationships while only few zones of interest will require testing. This study, therefore, developed empirical relationships between electrical resistivity sounding and cone penetrometer test data for engineering site investigation using a case study from the Basement Complex Terrain of Southwestern Nigeria. Regression analysis was used to assess the correlation between the soil resistivity and cone resistance and the validity of the empirical relation was evaluated by comparing values estimated from the soil resistivity vs. cone resistance cross plot with field values obtained from cone penetration tests. The values of allowable bearing pressure computed by using both values in Meyerhof’s equation were also compared with the allowable bearing capacity deduced with laboratory values of soil strength parameters (cohesion, angle of internal friction, soil unit weight) in Terzaghi’s general formula. The results show close agreement between the measured and estimated values with the differences typically less than 10%. The standard errors of the estimates for the cone resistance and allowable bearing capacity are 2.70 and 4.16 respectively, implying reliability of the estimates. The proposed empirical relationships, therefore, appear to provide reasonable estimation of soil cone resistance and allowable bearing capacity from soil resistivity. Few complimentary cone penetrometer and laboratory tests will thus be required while the cost and duration of site investigation for engineering structures are expected to reduce.

The use of Geoeletric Methods for Post-foundation Assessments of Distressed Buildings in Ebute-meta, Mainland Local Government Area of Lagos State

Geophysical and geotechnical investigations were combined to investigate the immediate causes of the distresses and foundation failures of buildings in Ebute-Meta area of Lagos, south-west Nigeria. Six (6) traverses were mapped in the study area across which six (6) 2D Wenner ERI, and fourteen (14) VES geophysical data were acquired. One (1) boring and five (5) CPT geotechnical data were also acquired. 2D ERI results reveal that resistivity values vary from 4.62 – 293 Ωm across the study area. Three resistivity structures were identified which denoted peat/clay, sandy clay, clayey sand and sand. The resistivity of the peat/clay varies from 4.62 – 27.9 Ωm with thickness varying from 12 - 25 m. The sandy clay varies in resistivity and thickness values from 26 – 86 Ωm and 8 – 29 m respectively. The clayey sand from 84.4 – 182 Ωm and 10 -15 m, and sand, having resistivity and thickness values of 293 Ωm and 3 – 5 m. The VES reveals similar results to the 2D ERI, delineating six geoelectric layers which are the topsoil, peat, clay, sandy clay, clayey sand and sand at maximum depth of 35.8 m. The borehole (BH) reveals a maximum boring depth of 45 m with eight zones comprising dark grey sandy clay, firm to stiff silty clay, soft, dark organic silty peaty clay, grey silty sand, dark grey silty sandy clay, dark grey organic peaty clay, grey silty sandy clay and medium dense to dense grey sand with occasional gravels. The CPT, which penetrated a maximum depth 15.8 m reveal that the cone resistance values vary progressively from 0 – 162 kg/cm2indicating very soft clay to soft clay near-surface and medium dense to dense geologic material at deeper depth. The peat/clay delineated by the 2D ERI and VES at 5 – 25 m depth with resistivity value varying from 4.62 -17 Ωm in the study area, and also revealed in the BH at 5.75 – 27.75 m depth as soft, dark organic silty peaty clay, having cone resistance values varying from 0 – 20 kg/cm2 is laterally extensive and incompetent to support engineering foundation.

KARAKTERISTIK TANAH TEMPAT PENGOLAHAN SAMPAH AKHIR DI KECAMATAN KOTA BANGUN KUTAI KARTANEGARA

Penelitian ini mengenai karakteristik tanah pada areal perencanaan pengolahan sampah. Metode yang digunakan adalah SPT, CPT dan uji laboratorium. Hasilnya adalah sebagai berikut: ke-empat titik CPT mempunyai nilai Cone Resistance Conus dari kedalaman 1 meter antara 19,78 -23,73 kg/cm2 dan pada kedalaman 4 meter bernilai 201,75 – 205,68 kg/cm2. Sedangkan nilai SPT pada kedalaman 1 meter antara 2 – 18 Blows/feet dan pada kedalaman 4 meter nilai N antara 29 – 45 Blows/feet. Uji laboratorium menunjukkan sifat tanah lunak tanah tersebut berwarna, dan batas Atterberg (LL dan PL) makin membesar.

Cone penetration tests in dry and saturated Ticino sand

It is commonly assumed that dry and saturated sands exhibit similar cone resistance–relative density relationships. Some studies pointed out that partial saturation and calcareous sands with considerable fines content are potential factors affecting these relationships. However, there is experimental evidence in Shaqour Bull Eng Geol Environ 66:59-70, (2006) that clean uncemented quartz sand may exhibit lower cone resistance in saturated conditions. The present study aims on contributing towards better understanding the effect of water saturation on cone resistance in sand. For this purpose, Ticino sand samples were prepared dry and saturated in a calibration chamber and cone penetration tests were performed over a wide range of relative densities and at two consolidation stresses. Overall, it was observed that dry and saturated samples exhibited similar cone resistances. Only slightly higher cone resistances were observed for dry samples at the lower consolidation stress. Two anomalous samples, which were tested dry at medium relative density, were found to exhibit way higher cone resistances than expected from published cone resistance–relative density relationships. The Young's modulus was observed to be proportional to cone resistance and independent of whether a sample was tested dry or saturated, being therefore considered as more robust soil property for cone resistance relationships.

CPTU identification of regular, sensitive, and organic clays towards evaluating preconsolidation stress profiles

<abstract> <p>Soil classification by piezocone penetration tests (CPTU) is mainly accomplished using empirical soil behavior charts (SBT). While commonly-used SBT methods work well to separate fine-grained soils from granular coarse-grained soils, in many instances, the groupings often fail to properly identify different categories of clays, specifically: (a) "regular" clays that are inorganic and insensitive, (b) sensitive and quick clays; and (c) organic soils. Herein, a simple means of screening and sorting these three clay types is shown using three analytical CPTU expressions for evaluating the preconsolidation stress profile from net cone resistance, excess porewater pressure, and effective cone resistance. A number of case studies are utilized to convey the methodology.</p> </abstract>

Correlation Between Cone Resistance Values and Cohesion Values in Cohesive Soils (Case Study in Gunung Anyar District)

The physical and mechanical properties of the soil can be determined based on laboratory tests by testing soil samples obtained from field drilling. At one point it can be done simultaneously between SPT testing and drilling. Therefore, it can be known simultaneously the value of N-SPT with the physical and mechanical properties of the soil. The purpose of this study was to obtain a relationship between the cone resistance value (qc) obtained in the field and the cohesion value for cohesive soil types. This study uses primary data, and secondary data. The results of the correlation between the cone resistance value (qc) obtained in the field and the cohesion value for cohesive soil types show a strong correlation. This is indicated by the regression value which reaches a value of 0.75, which is 0.7809. The regression equation obtained is y = 0.0138x – 0.0063. The coefficient of the cone resistance value is 0.0138, indicating that every 1 constant increase in the cone resistance value variable will increase the cohesive value in the cohesive soil by 0.0138. The positive regression coefficient indicates that the higher the cone resistance value (qc), the higher the value of cohesion (c) for cohesive soils.

Instrumented Cone Penetrometer for Dense Layer Characterization

Subsurface characterization is essential for a successful infrastructure design and construction. This paper demonstrates the use of an instrumented cone penetrometer (ICP) for a dense layer characterization at two sites. The ICP consists of a cone tip and rods equipped with an accelerometer and four strain gauges, which allow dynamic driving, in addition to quasi-static pushing of the cone. The force and velocity of the cone are measured using the ICP instrumentation and compared with the N value, dynamic cone penetration index, and static cone resistance. A strong correlation has been observed between the total cone resistance estimated from the ICP and the dynamic cone penetration index and static cone resistance. After the correction of the dynamic cone resistance effect, the static component of the total cone resistance can be used as an alternative to a static cone resistance. This novel approach of soil resistance estimation using the ICP may be useful for dense layer characterization.