Variability Of Penetration Resistance Research Articles

Variability in jacking resistance of adjacent steel pipe piles under controlled pile installation

The pile bearing capacity varies even within the same site. This study aims to gain a better understanding of the effect of pile penetration techniques on the variability of bearing capacity. The study uses data from 83 jack-in test piles to explore the variations in penetration resistance at the pile head, base, and shaft. The semivariance increases with an increase of the horizontal distance, so we focus on the semivariance between 5 m range, whose error was defined as the error due to piling workmanship. The analysis shows that the errors follow a lognormal probability distribution, and the coefficient of variation (COV) in penetration resistance at the heads and bases is about 10%, while the COV in extracted resistance varies widely, with a range of 5–25%. Little difference in the variations due to piling workmanship was observed among different penetration motions, speeds, and soil types.

Sugar as an Analogue for Snow in Penetration Testing: A Preliminary Comparison

Snow is a sintered matrix of ice, the strength of which is determined by the number and size of bonds between ice grains. However, because snow is a thermally unstable material, it is problematic to transport and store samples for accurate ex situ testing of mechanical behaviour. As an analogue for snow, we examined the sintering behaviour of different types of granular sugar at different humidities over different temporal periods and then assessed the extent of sintering and resistance to penetration of these samples. Like snow, increased sintering occurs in sugar over time. Sintering extent and rate are affected by the humidity environment and penetration resistance generally increases after increased sintering time. This preliminary examination suggests that in the absence of snow testing facilities, humidity-controlled sintered sugar may serve as a valuable proxy for examining the temporal variation of penetration resistance in snow.

Defining tillage need for edible bean production under no-tillage: Classical and time series analyses

Mechanical amelioration techniques may be used in long-term no-till compacted soils to improve soil structure and increase crop yield. The objectives of this study were to investigate the effect of ploughing and chiseling on changes in soil physical properties, quantify the number of days that the soil moisture is outside the critical limits of the least limiting water range, compare crop performance, and define the best tillage method using classical and applied statistical analysis. Treatments consisted of continuous no-tillage for 5 years (NT), disc plough (Plo) and chisel plough (Chi) both on soil previously under no-tillage for 5 years. High degree-of-compactness and low least limiting water range on the medium-term no-tillage Acrisol justified the need for evaluating inverting and non-inverting tillage. Soil penetration resistance, dry bulk density, soil temperature, and volumetric moisture content was measured at different times and soil layers during bean growth and development, and correlated with black bean roots distribution and yield. Soil moisture content and temperature data were subjected to time-series analysis. Low penetration resistance was observed in the 0.03 – 0.05 m soil layer, which was greater in NT than in Plo or Chi soil, but always below 1.5 MPa. During the cropping season, spatial variations in penetration resistance was lesser in the deep soil layers compared to the surface layers, following the trend on lower oscillations in soil moisture. Soil bulk density at 0.075 m depth decreased due to soil disruption: 1.72, 1.65 and 1.52 Mg m−3 for NT, Chi and Plo, respectively, and increased with soil depth. The number of days the soil was in good moisture conditions had the order Plo ≈ Chi > NT. Although no-till soil is near the critical/restrictive condition to crops and soil tillage improves soil quality, tilling does not guarantee increased crop yield. The degree-of-compactness and the least limiting water range do not capture soil physical quality for bean growth and yield. Soil tillage influenced the autocorrelation and cross correlation of soil water content in all soil layers. The estimation of soil water content using state-time analysis was affected by soil management, with the best performance from Chi soil. Significant temporal relations were observed between soil water content and other soil-atmospheric variables, with rainfall being the highest controlling factor. The time series analysis can be combined with classical and spatial statistics, for assessing soil quality under different management based on local environmental properties and climatic conditions.

Soil heterogeneity after recultivation: ecological aspect

Abstract The study subject was the soil heterogeneity at a recultivation site Nikopol manganese-ore basin (Pokrov, Ukraine). The soils at the locality are sod lithogenic soils developed on gray-green clays. The study ran by applying soil penetration resistance indices. The penetration resistance was measured across a regular grid of 7 × 15 points (21 × 45 m). The distance between the measurement points was 3 m. The parameters were recorded at every 5 cm to a depth of 50 cm. The environmental parameters were determined by phytoindication. Geostatistical analysis showed the average level of spatial dependence of soil penetration resistance. According to the features of the profile variation in penetration resistance with the depth, the measurement points have been divided into three clusters. The clusters formed morphologically homogeneous soil areas. These areas significantly differed in their soil acidity and in nitrogen content in soil.

Borçka Barajı Rezervuarında Yeni Oluşmuş Bir Sediment Birikim Sahasındaki Penetrasyon Direnç Değerlerinin Uzaysal Dağılımı

This study was conducted to analyze vertical and horizontal spatial variability of penetration resistance (PR) in recently deposited sediments at Borcka Dam reservoir. Ninety-one grids with 50 m by 10 m were located and PR was measured to a depth 80 cm by 10 cm increment (8 layers) within each grid. Spatial variation of PR was assessed by geostatistical techniques in all 8 layers. Semivariograms of PR were constructed for all the layers and corresponding kriging maps were built. The PR values were greater in surface layer (0-10 cm) and gradually decreased by depth. Mean PR was greatest (0.747 MPa) in surface layer and lowest (0.413 MPa) in 61-70 cm (layer 7). Results from exploratory statistics and geostatistical analyses showed that the PR values were more variable in surface layer compared to those in deeper layers due to that the surface layer was drier at the sampling and that affected by environmental factors in a greater extent. All the studied layers exhibited differences in spatial variation of PR as sill, nugget, and range values of corresponding semivariograms and kriging-predicted surface maps showed. The shortest geostatistical range (40.8 m) occurred of surface layer while longest (173.3 m) occurred for second layer (11-20 cm). The nugget effect was greatest (44%) in third layer (21-30 cm) while lowest (13%) in the surface layer. The same study may be repeated with more variables to understand mechanisms behind development and extent of spatial variation in these newly deposited sediments.

Changes in soil compaction indicators in response to agricultural field traffic

In addition to measurements of soil bulk density, compaction is usually measured by changes in soil porosity and penetration resistance. The effects of agricultural field traffic on changes in soil compaction indicators were investigated, a) to quantify the immediate effects of field traffic on the degree of compactness, penetration resistance, and matric suction and b) to evaluate the behaviour of these variables as indicators of post-traffic compaction on soils with different clay content. Two wheeling experiments were performed on two oxisols containing 200 (sandy clay loam) and 480 g kg−1 [clay] (i.e. clay soil). Compaction occurred after wheeling in both soils, but the degree of compactness was higher for the clay soil. Texture affected the behaviours of penetration resistance and matric suction in detecting compaction. With the increase in clay fraction, friction effects diminished, and variation in penetration resistance was not significant, even with compaction. Reductions in soil porosity due to compaction can cause variation in pore size and in the degree of saturation, altering the water retention energy. Due to the proportionally smaller pore size, this mechanism was detected via matric suction at approximately field capacity only for the clay soil. For the sandy loam soil, it is likely that only a larger reduction in porosity and variation in the degree of saturation impose detectable changes in matric suction.

PROPOSED BURIED WEIGHT TEST AS METHOD OF TESTING FOR SETTING TIME OF CONCRETE MIXTURES

In this study, we examined method of test for setting time of concrete mixtures. Generally, the setting time of concrete mixtures is demanded by variation of penetration resistance, which is measured by manual labor for about eight hours. This measurement takes considerable effort. In late years, automatic devices to measure penetration resistance are commercially available, however the price is high. To solve these problems, we proposed a new low-effort and low-cost method: Embedded Weight Test. In the Embedded Weight Test, an embedded weight is hung with a line in the concrete mixture, and the tension of the line is measured by a data logger. The tension of the line had a variation point. The variation point is regarded as the time when the concrete mixture begins to vary from liquid to solid. As a result pf Embedded Weight Test with cement paste, the variation point of the tension was correlated with the initial setting time, which was defined by ISO 9597.Similar results were obtained when Embedded Weight Test was carried out with mortar. The variation point of the tension was correlated will help to estimate the time such as limits from mixing to the completion of placing or limit for intervals placing operations.

Piezoelectric ring actuator technique to monitor early-age properties of cement-based materials

Piezoelectric ring actuator technique (P-RAT) that uses shear wave velocity (VS) was initially developed as a non-destructive test for soil characterization. The P-RAT was successfully modified to be adapted for cement-based materials in previous research by the co-authors. In the current study, validation of the P-RAT was carried out by comparing VS test results to those of conventional tests used to evaluate early-age properties of cementitious materials. Conventional tests included monitoring variation in penetration resistance for mortar, Vicat needle for paste, calorimetry, and electrical conductivity with time at early ages. The validation involved testing paste and mortar mixtures prepared with ordinary Portland cement and water-to-cement ratios (w/c) of 0.35–0.50 and different types and dosage rates of chemical admixtures. Test results showed that derivation of VS-versus-time curve obtained from the P-RAT can be employed to determine setting time. The variations of VS with time resulted in similar behaviour as those of the variations of heat of hydration and electrical conductivity with time. Fundamental relationships between VS results of the P-RAT and conventional tests to monitor setting were established. An analytical model to estimate the w/c at early age was proposed using the VS approach.

An effective stress framework for the variation in penetration resistance due to episodes of remoulding and reconsolidation

Steel catenary risers (SCRs) are used to transport hydrocarbon products between offshore floating platforms and the seabed. Like many offshore structures, SCRs are subjected to gross cyclic movements during operation, which remould the seabed soil. The fatigue life of these structures is highly sensitive to the stiffness and strength of the seabed response. Accurate modelling of this behaviour requires a framework that can capture the changes in soil strength and stiffness that occur throughout the design life, accounting for remoulding during extreme events, and reconsolidation during the intervening periods. This paper describes such a framework, which is couched in effective stress terms. Soil softening during remoulding is predominantly associated with excess pore pressure generation, and the subsequent regain in strength is linked to the dissipation of excess pore pressure. The framework can describe the variation of resistance on a cylinder (i.e. a pipe) during any sequence of vertical cyclic motion, interspersed with pause periods. The framework is based on a critical state approach, with the current strength being linked to the current moisture content. The framework is shown to capture well the load–penetration response during an episodic T-bar penetrometer test. The operative soil strength is shown to vary dramatically throughout this event, with the softening effect of remoulding being almost entirely negated by a regain in strength associated with periods of partial or complete reconsolidation. The framework provides a basis for capturing these dramatic effects to aid pipeline and riser design (and other processes that involve gross remoulding and reconsolidation), without recourse to a full numerical simulation of the entire soil domain.

Soil penetration resistance, a suitable soil property to account for variations in root elongation and branching

Root system development is affected by soil conditions. The effects of bulk density, water content and penetration resistance on root development processes were investigated in peach trees. Peach tree rootstocks were grown in various soil conditions, combining two bulk densities (1.2 and 1.5 g soil.cm-3) and three water contents (0.14, 0.17 and 0.20 g.g-1soil). Root parameters (tip diameter, length of apical unbranched zone, branching density and diameters of main and lateral roots) and plant growth (leaves, branches, trunk, root dry mass) were measured. Root growth processes (elongation, branching) were studied using relationships between root parameters. The proportion of biomass allocated to each plant compartment was similar whatever the soil conditions. Variations in root development were best explained by the variation in penetration resistance, rather than other soil properties. Increased soil penetration resistance reduced the root elongation rate, especially for thick roots. In addition, the branching pattern was affected. In soil with a high penetration resistance, the root system shape differs from a typical herringbone pattern. These results allow quantification of the root system plasticity, and improve our understanding of the interactions between root development and soil properties.

The potential restriction to root growth in structurally weak tropical soils

The penetration resistance was measured in undisturbed cores equilibrated at two matric potentials for three weakly structured soils from Nigeria. Within and between sites differences provided a wide range of dry bulk densities and water contents. Penetration resistance was inversely related to water content and significant whilst the relationship with dry bulk density was not significant. At −6 kPa matric potential (field capacity) penetration resistances were less than 1.5 MPa while at −100 kPa matric potential they were near to or greater than 2 MPa. The results suggest that potential restriction to root growth is likely to occur when such soils dry to a matric potential of < − 100 kPa. Across soils the variation in effective stress accounted for 62% of the variation in penetration resistance. For cores equilibrated at −100 kPa matric potential the penetration resistance was strongly correlated to unconfined compressive strength and indirect tensile strength of cores 23 mm in diameter and 40 mm in length (referred to as minicores). This suggests that the minicorer technique may be useful for rapidly assessing the root restricting behaviour of such soils. Critical values of unconfined compressive and indirect tensile strengths corresponding to a penetration resistance of 2 MPa, lower limit of restricted root growth in these soils were 28 kPa and 7.7 kPa, respectively.

Spatial variability in penetration resistance of a hardsetting tropical alfisol

Geostatistical techniques were used to analyse the spatial variation of penetration resistance on an experimental plot intended for root studies. Penetration resistance was measured at two soil water conditions. Penetration resistance exhibited spatial structure but the models describing the semivariograms were different for the two soil water conditions. An isotropic linear model provided the best fit for penetration resistance in the dry soil while an isotropic spherical model was used for penetration in the wet soil. A complementary study of the spatial structure of water content also showed a similar trend. Cross-semivariograms were constructed to determine the spatial relationship between penetration resistance and water content. Penetration resistance in the dry soil was negatively correlated with water content. The nugget variances as the percentage of the sill in the wet soil data set suggest that the topsoil was slightly more variable than the subsoil. The spatial scale of variation in penetration resistance of the wet soil was 33 m at 7.5 cm depth and 20–27 m at 15–30 cm depth. Punctual kriging was used to estimate the penetration resistance and water content values. The estimated values are presented as contour maps. The pattern of variation and the underlying possible processes for the variation are discussed. The results suggest that the likely influence of spatial variation of soil properties on crop growth may have to be considered in modelling in order to simulate the real field situation.

Use of a penetration resistance characteristic to predict soil strength development during drying

Rapid drying of hardsetting soils frequently results in poor seedling emergence. Prediction of seedling response to seedbed strength requires an understanding of the manner in which soil strength develops during drying. Penetration resistance is an empirical estimate of the cavity expansion pressure required of the emerging seedling. However, use of penetration resistance to predict soil strength during drying is hampered by the greater error in penetration resistance vs. bulk soil strength measurements, uncertainty over the role of drying rate in strength development, and limitations in the theoretical basis of penetration resistance compared with other strength quantities. In this experiment we measured the penetration resistance, shear strength and tensile strength development during drying of a hardsetting red-brown earth following flood irrigation. The results showed first, that although penetration resistance had a slightly higher coefficient of variation, ease of replication resulted in penetration resistance having substantially smaller 95% confidence interval than either shear or tensile strength. Second, soil strength developed more rapidly at high drying rates; however, variation in penetration resistance was accounted for by changes in soil water content ( r 2 = 96%). Therefore drying rate did not influence the soil strength characteristic. Third, penetration resistance was a linear function of effective stress as predicted by theory, and unlike the bulk strength measures did not deviate within the range of water contents measured. We conclude that the penetration resistance strength characteristics can be used to predict seedbed strength in hardsetting soils for a wide range of packing, wetting and drying conditions.

Seasonal variation in penetration resistance and shear strength of three rainforest soils from northeastern Queensland : Spain, A V; Prove, B G; Hodgen, M J; Lee, K E GeodermaV47, N1/2, Aug 1990, P79–92

Seasonal variation in penetration resistance and shear strength of three rainforest soils from northeastern Queensland : Spain, A V; Prove, B G; Hodgen, M J; Lee, K E GeodermaV47, N1/2, Aug 1990, P79–92

Seasonal variation in penetration resistance and shear strength of three rainforest soils from northeastern Queensland

Large seasonal changes were noted in field measurements of penetration resistance and shear strength over the course of a sixteen-month study in three tropical soils supporting rainforest. Both penetration resistance and shear strength levels were seasonally higher in soils of basaltic origin than in those formed from alluvial or metamorphic parent materials. Both measures of soil strength clearly decreased with increasing gravimetric water content at all sites. Significantly increased penetration resistance with increasing bulk density was noted at all sites, although the variance accounted for by this variable was small. Shear strength was not significantly related to bulk density. Conversion of these soils to sugarcane culture has led to marked increases in surface-soil bulk density and strength, with the formation of a compacted zone close to the soil surface.

Mutual relationship between patterns of soil penetration resistance and root radial expansion growth of upland rice.

The root boxes (24cm×2cm×40cm) filled with soil at two different soil bulk densities of 1.33 g/cm3 (control) and 1.50 g/cm3 (compact), were prepared for studying mutual relationship between the variation of penetration resistance as a function of soil depth and radial expansion growth of root axis. Upland rice was grown under both soil conditions for two weeks, and the root systems were sampled by pinboard method. Penetration resistance determined by a developed penetrometer showed several peaks of resistance throughout the entire depth of the root boxes caused by the presence of soil boundary layers resulting from the procedure of soil filling up. There were also found variations of root diameter of seminal axis and lst order lateral roots emerged from the seminal axis as a function of soil depth. In the compact plot, patterns of the penetration resistance corresponded well with those of root diameter. However, in the control, the correspondence of both patterns was not as clear as in the compact. These results indicated that patterns of soil mechanical impedance along the entire depth of the root box could be recorded in root axes as the history of radial expansion growth when root tips were exposed to higher mechanical impedance. The result obtained in this experiment suggested the necessity of considering the patterns of soil mechanical impedance in the growth media for the study of root-soil interaction.

Laboratory studies of crust development in Irish and Iraqi soils II. Effects of some physico-chemical constituents on crust strength and seedling emergence

The influence of soil constituents including sand, silt, clay, organic substances, aluminium and iron on crust development and seedling emergence was investigated in a selection of 30 soils. After treatment with simulated rain, soil crust strength as measured by penetration resistance to an upward-moving probe tended to decrease with increasing total organic carbon content, but the relationship was not a simple one. Consideration of other factors showed that in some soils (soils of 1.5–2% total organic carbon), alkali-exractable carbon and clay contents had the greatest influence on penetration resistance values whereas in other soils (2.4–3% total organic carbon), coarse sand, fine sand, EDTA-extractable aluminium and humic acid carbon were highly correlated with penetration resistance. In a group of soils with around 4% total organic carbon, oxalate-extractable aluminium appeared to exert a dominant influence. There was a good correlation between humic acid carbon and penetration resistance after rain treatment in soils containing less than 40% sand. A similar relationship was also noted with EDTA-extractable iron. Combination of all factors in a multiple regression analysis accounted for a considerable proportion of the variation in penetration resistance of soils with and without simulated rain application and in seedling emergence of barley. Organic carbon, and the humic acid fraction in particular, were most important in determining crust strength for all soils as a group. A significant correlation between plastic limit moisture and the logarithm of penetration resistance is explained partially, at least, by the relationships that exist between organic carbon alone, clay alone and a combination of both, with variation in moisture.

Evaluating Penetration Resistance and Wheel Sinkage Response to Soil Water Suction Changes in a Draining Clay Soil

AbstractTo facilitate the development of subsurface drainage design criteria for the reduction of soil compaction, the relation between the bearing capacity of nearly saturated soil and its water suction(s) is analyzed for a cone penetrating into the soil and for a sinking tractor wheel. Approximate equations are developed, from basic soil mechanic theory, for certain soils under a limited range of suction and loading conditions. The main assumptions are attainment of plastic equilibrium during dynamic loading and independence of the soil deformation process and its shear failure pattern of suction. The penetration resistance‐suction model shows that a linear response to suction changes can be expected, characterized by a modified bearing capacity‐suction factor (Ns) which may be estimated from the mechanical and water properties of the soil. The wheel sinkagesuction model predicts the relative change in wheel rut depth in response to loading (inflation pressure) and suction changes, by means of the same Ns parameter. Tests were conducted in plowed (P1) and unplowed (P0) irrigated plots of a clay soil, utilizing a cone penetrometer and a tractor with differentially loaded and differentially inflated rear wheels. Variations in penetration resistance with suction were successfully predicted, assuming local, intermediate, and general shear failure in the subsoil, and in the plow‐layers of P1 and P0, respectively. The relative change in wheel rut depth with suction was found predictable, provided S &gt; Smin. The transition from S &gt; Smin to S &lt; Smin was characterized by an inversion of sinkage response in P0, and by a transition from vertical to horizontal soil compaction or flow in P1.