Deep Clayey Soils Research Articles

Field study on installation effects of pre-bored grouted planted pile in deep clayey soil

This paper presents the results of field tests performed to investigate the installation effects of pre-bored grouted planted (PGP) pile in deep clayey soil. The variation of horizontal soil displacements, excess pore water pressures and lateral soil pressures was measured in the PGP pile installation process. The test results show that the drilling and grouting process induced large horizontal soil displacements in the soil within a radial distance of 2 d ( d is pile diameter), and the maximum horizontal soil displacements induced by the drilling and grouting process were smaller than 15.9 mm when the radial distance reached 4–5 d. Moreover, the horizontal soil displacements decreased along the soil layer depth, as the superficial soil layers were of small deformation modulus and lateral soil pressure. The drilling process brought large excess pore water pressures in the soil when the radial distance was less than 3 d, and the excess pore water pressures induced by the drilling stage were all less than 55 kPa when the radial distance reached 4–6 d. The drilling process also induced some lateral soil pressure increases in the soil within a radial distance of 3 d, while the measured maximum lateral soil pressure increases were smaller than 10.9 kPa when the radial distance increased to 4 d. On the whole, the excess pore water pressures and lateral soil pressure increases induced by the installation of PGP pile were much smaller than that induced by the installation of driven PHC pile. Moreover, the horizontal soil displacements, excess pore water pressures and lateral soil pressure increases induced by the installation of PGP pile all recovered rapidly after the installation of pile, as the cemented soil in the pile hole was in liquid state after the drilling and grouting stage.

Experimental study on consolidation characteristics of deep clayey soil in a typical subsidence area of the North China Plain

Land subsidence is an important environmental problem in the North China Plain (NCP). A typical subsidence area mainly located on adjoining areas of Beijing and Hebei provinces was selected to study the consolidation characteristics of deep clayey soil. Clay samples were collected from 14 boreholes at different depths, and the compression and consolidation behavior of the soil was analyzed by high-pressure oedometer tests. Results show that the deformation amount and deformation stabilization time in the primary consolidation stage increase with the load but decrease with the sampling depth. The nonlinear compression model of e-log(p) does not fit well for deep normally-consolidated clayey soil, the log(e+ec)–logp model fit the shallow clayey soil better than the deep clayey soil, and the hyperbolic model fits almost all soil samples well. Based on statistical theory, the soil consolidation equation CE_NCP was established for calculating the relationship between the degree of consolidation and the time factor in subsidence areas. The equations were fitted with the data obtained from high-pressure consolidation tests to obtain three parameters a, b and c, which are applied to the consolidation calculations for soil samples at depths of 0–100 m, 100–200 m, 200–300 m and 300–400 m, respectively. The applicability of CE_NCP equation was evaluated by comparing it to the analytical solution of Terzaghi’s consolidation equation, results showing that CE_NCP equation is more suitable for the calculation of the consolidation in the study area than the Terzaghi’s analytical solution. Eventually, the CE_NCP equation was successfully used to estimate the degree of consolidation in a subsidence area of Lang Fang City in the NCP.

Field behavior of pre-bored grouted planted nodular pile embedded in deep clayey soil

This paper presents the results of field tests performed to investigate the behavior of pre-bored grouted planted nodular (PGPN) pile embedded in deep clayey soil. The test piles were all instrumented to measure the shaft and tip resistance and to determine the load transfer along the pile shaft. The test results show that the displacement necessary to fully mobilize the shaft resistance of PGPN pile is in the range of 1.83–3.32% D (D is pile diameter), and that the ultimate skin frictions of grout–soil interface of different soil layers are larger than the conventional proposed ultimate skin frictions for non-displacement piles. Furthermore, the pile tip resistance accounts for about 16% of the total applied pile head load corresponding to a pile head displacement of 0.1 D, and the pile tip resistance continues to increase after tip displacement reaches 5% of pile tip diameter.

Deformation of the aquifer system under groundwater level fluctuations and its implication for land subsidence control in the Tianjin coastal region.

This study demonstrates characteristics and mechanisms of deformation of an aquifer system in response to seasonal fluctuations of groundwater level when groundwater pumping has been strictly regulated after experiencing longtime land subsidence. Two boreholes with depth of 1226m (G2 site) and 905m (G3 site) were drilled at the Tianjin coastal region where severe land subsidence had occurred since the 1950s. Extensometer/piezometer groups installed at the G2 site illustrate synchronized variations of compaction and groundwater level since 2010 in the aquifer system between depth of 100-400m which contributes most groundwater pumpage. Monitored land subsidence demonstrates that the shallow aquifer has become the main contributor to the land subsidence, and inelastic compaction still occurred in the aquifers where groundwater level has recovered. Pre-consolidation stresses show that clayey soils in depth < 100m are under-consolidated, and deep clayey soils show the state of normal- to over-consolidation. The effects of the cyclic groundwater level oscillation on deformation were investigated using repeated loading and unloading tests. Void ratio changes in loading/unloading cycles illustrate that inelastic deformation rate decreases gradually and elastic deformation rate remains almost unchanged with increases of cyclic numbers. The deformation of soil samples from 100 to 400m is mostly elastic for loading stress in the over-consolidation stress range. These findings suggest that groundwater dewatering in the shallow (depth < 100m) aquifer will be the primary target to control land subsidence. Groundwater level fluctuations higher than pre-consolidation value in 100-400m only lead to elastic and recoverable deformation even small residual permanent deformation may continue for a long time. The results improve the understanding of deformation in complex urban aquifers affected by groundwater level fluctuations and highlight the importance of city planning management for controlling land subsidence in coastal cities.

Fingerprinting sediment sources in a large agricultural catchment under no‐tillage in Southern Brazil (Conceição River)

AbstractBrazil is a leader in the adoption of conservation agriculture practices and technologies. However, the impact of these practices on sediment sources at the catchment scale has not been quantified yet, particularly in grain growing regions, where a conservationist no‐tillage system is implemented to protect soils. To address this knowledge gap, a sediment fingerprinting study based on elemental geochemistry was carried out in a large agricultural catchment (804 km2) of Southern Brazil where no‐tillage practices dominate. A total of 156 soil samples were taken to characterize the three main potential sediment sources: cropland (n = 79), unpaved roads (n = 41), and channel banks (n = 36). Sediment sampling was performed using a time‐integrated sampler (n = 33) and by collecting fine‐bed material (n = 34) at five locations across the catchment. Sediment was also sampled during flood events at the catchment outlet (n = 20). Sediment source contributions were calculated using an optimal suite of geochemical properties and a mixing model. Results showed that although the catchment is not particularly sensitive to soil erosion (i.e., deep clayey soils with gentle slopes), the amount of sediment supplied by cropland to the river network remains very high (up to 1.63 Mg·ha−1·year−1). Sediment fingerprinting results showed that even when no‐tillage is implemented, cropland remains an important source of sediment, supplying up to 70% of the material transiting the Conceição River. Accordingly, the current conservation farming system in this catchment needs to be improved to further reduce soil erosion and sediment yield.

Settlement prediction and behaviour of pile foundations in deep clayey soil deposits

A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a proposed empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils; consequently, the finite element Plaxis 3D program can be a useful tool for numerical analysis. The numerical analysis is modified by adjusting the calculation of compression modulus from those obtained under pressure between 100–200 kPa by which the results of the settlement are modified and thus matching the realistic measurements. The absolute error is 3 mm which is accepted compared with the last researches. This scenario can be applied for the similar problems in the theoretical applications of deep foundations.

Engineering properties of vertisols.

Vertisols are deep clayey soils, with more than 45% clay, dominated by clay minerals such as smectites, which expand upon wetting and shrink upon drying. The most important physical characteristics of Vertisols are a low hydraulic conductivity and stickiness when wet and high flow of water through the cracks when dry. They become very hard when dry and in all the time are difficult to work. During the rainy season, the cracks disappear and the soil becomes sticky and plastic with a very slippery surface which makes Vertisols hardly trafficable when wet. Water movement in soil that change volume with water content is not well understood and the management of swelling soil remains problematic. Swelling or shrinking result in vertical displacement of the wet soil, which involves gravitational work and contributes to an overburden component to the total potential of the soil water. Many swelling soils crack and the network of cracks provides pathways for rapid flow of water, which prejudice application of theory based on Darcian flow. One – dimensional flow of water in a swelling system requires material balance equation for both the aqueous and solid phases. The analytical data offers some values of particle – size distribution, compression, swelling degree and pressure, plasticity index, elastic modulus, triaxial shear, angle of shear and load carrying capacity in order to realize a foundation study for some constructions. ©2012 Author(s) CC Attribution 3.0 Unsuported License.

Bioenergetic potential of agricultural soils in Slovakia

Knowledge of the energy potential of an agricultural soil and the potential production of biomass, together with economic parameters, can help pinpoint more effective sites for growing plants for traditional purposes and for fuel production. There is approximately 10 206 PJ of potential energy accumulated in Slovakia's agricultural soils. The lowest utilisation was found in the Cambisols soil type (0.7–1.8%) and the highest in Regosols (3.1–7.0%). The bioenergy production potential of agricultural soils in Slovakia was determined for chosen soil parameters according to the production of the plants grown. With regard to energy, the most productive are soils of the Chernozem type (25.1 MJ m−2) and Mollic Fluvisols (22.5 MJ m−2). Gleysols, Histosols, Solonetz and Leptosols (3.0–5.0 MJ m−2) produce the lowest bioenergy levels. The highest energy production precondition (22.2 MJ m−2) occurs in soils in the very warm, very dry lowland climatic region. According to the granularity, the most energy (14.0–15.0 MJ m−2) is produced by deep clayey soils (18.0 MJ m−2) in a slope to 3° (18.3 MJ m−2) that are not or sporadically gravelly (19.2 MJ m−2). The highest energy yields can be expected from the biomass of plants grown in arable land (approximately 11.0 MJ m−2). Regarding the efficiency of economic and financial inputs, plants growing in Chernozem, Mollic Fluvisols, Fluvisols and Haplic Luvisols soil types in very warm, very dry, lowlands to warm, very dry, basin-like, continental climatic regions appear to be profitable in slopes to 7°, with no or only a sporadic gravel content.

SPATIAL VARIABILITY IN FOREST WATER USE FROM THREE CONTRASTING REGIONS OF SOUTH-EASTERN AUSTRALIA

Forest water use estimates derived from sap flow measurements in three contrasting regions of south-eastern Australia were compared. In each region, annual evapotranspiration was highly spatially variable, influenced by water availability, potential evapotranspiration, soil depth and texture, groundwater depth and salinity and at one site by species. In a low rainfall region (mean precipitation -400 mm year -1 ), ET in five irrigated eucalypt plantations ranged from 415 mm year -1 by Eucalyptus grandis W.Hill ex Maiden at a site with deep clayey soil and high salinity groundwater to 1277 mm year -1 by Corymbia maculate (Hook.) K.D.Hill & L.A.S. Johnson, at a site with loamy soil and low saline groundwater. On the same site, ET in a plantation of E. grandis was only 928 mm year -1 . In a medium rainfall region (mean precipitation 657 mm year -1 ), in gently undulating terrain containing large-scale plantations of Pinus radiata D. Don and Eucalyptus globulus Labill., fresh groundwater (EC -1 ) was often present but at depths varying from less than 2 m to greater than 20 m. Among 22 study sites, rainfall varied spatially from 362 to 800 mm year -1 but ET varied from 560 to 1414 mm year -1 . About 94% of this variation was explained by water availability from rainfall and groundwater and by potential evapotranspiration. In the highest rainfall region (precipitation ~1200 mm year -1 ) within a 1.2 km 2 catchment covered by native eucalypt forest in steep, mountainous terrain, annual ET varied by up to 63% between four study sites. In all three regions, only sapflow measurements would have revealed the high spatial variability in mean annual transpiration and ET that occurred over distances of <1 km. Alternative measurement methods often cannot provide data at a small enough scale to allow a complete understanding of the most important variables influencing forest water use.

Geological and environmental issues of the proposed link canal (Inchampalli to Nagarjunasagar) of Godavari to Krishna Rivers adopting remote sensing and geographical information system (GIS)

Extremely erratic rainfall, unevenly distributed and very heavy precipitation in short time resulting in flash floods and inundation in India became a usual phenomena in recent years. At every event, a huge quantity of water is being wasted into the sea as run-off quite frequently due to inadequate harvesting structures. This huge run-off / surplus water can be harvested through the proposed linking of river basins envisaged by National Water Development Agency (NWDA). Out of the total mega projects, the NWDA suggested three link canals from Godvari to Krishna basin, to harvest the surplus water as well as to transfer flood water from Godavari. The Godavari (Inchampalli) - Krishna (Nagarjunasagar) link canal and its possible impact on the socio-economic and infrastructural forms the present study. The link canal of length 299 km (including a tunnel of 9.150 km) is proposed in the upper reaches connecting Godavari and Krishna basins succeeded by two other links towards their downstream. It takes off from the foreshore of the Inchampalli reservoir and joins the existing Nagarjunasagar via Musi reservoir. IRS-1D, LISS-III data is analysed for morphological, geological and land use/land cover information. Geology, geomorphology and soil base maps were obtained and updated with remote sensing data and their aerial distribution in the study area was discussed. The study includes 10 km buffer area on either side of the alignment and the proposed canal command area (5157.48 Sq km) spread in Warangal and Nalgonda districts. The canal command area is occupied by dry land and wasteland classes. Pediplain weathered is the main landform that occupied major part of the study area. The study area in Warangal district is mostly occupied by unclassified crystalline rocks of Archean age. Fine to medium grained, granite gneisses and migmatities of older metamorphics from chainage 102 km to the end point of the canal. Deep loamy soil, deep clayey soil, deep clayey calcareous soil and gravelly clay soils are dominant in the canal study area. Clayey and loamy soils are suitable for wet / dry crops and gravely calcareous for plantations and dry crops. The study revealed that 23 villages are to be rehabilitated while executing the canal and about 816 villages would benefit from it by way of drinking water / groundwater in addition to crop requirements. Key words: Link canal, donor basin, command area, geomorphology.

Water Use of Tree Lines: Importance of Leaf Area and Micrometeorology in Sub-Humid Kenya

In this research the relative importance of leaf area and microclimatic factors in determining water use of tree lines was examined in sub-humid Western Kenya. Measurements of tree water-use by a heat-balance technique, leaf area, bulk air saturation deficit, daily radiation, and soil water content were done in an experiment with tree lines within crop fields. The tree species were Eucalyptus grandis W. Hill ex Maiden, Grevillea robusta A. Cunn. and Cedrella serrata Royle, grown to produce poles on a phosphorus-fixing Oxisol/Ferralsol with (+P) or without (−P) phosphorus application. Doubling the leaf area of Cedrella and Grevillea doubled water use in a leaf area (LA) range of 1–11 m2 per tree. The response of Eucalyptus water use (W) to increases in leaf area was slightly less marked, with W = LA n , n<1. Transpiration rate per unit leaf area (Tr) was the other important determinant of water use, being affected by both tree species and phosphorus fertilization. A doubling of the saturation deficit (SD) halved the water use of all trees except for Cedrella +P, in which water use increased. A direct effect of soil water content on water use was only found in Grevillea -P, with a small increase (60%) as available water increased from 1.4 to 8.9% above wilting point (32%). This low direct response to soil water content is probably due to the extensive tree-root systems and the deep clayey soils supplying sufficient water to meet the evaporative demand. Indirect responses to soil water content via decreases in leaf area occurred in the dry season. The results showed that water use of tree lines was more determined by leaf area and transpiration rate per unit leaf area than by micro meteorological factors. The linear response of tree water use to leaf area, over a wide range leaf areas, is a specific characteristic of tree line configurations and distinguished them from forest stands. In tree lines light interception and canopy conductance increase with leaf area much more than a similar leaf area increase would have caused in a closed forest canopy.

Influence of selective tree cutting, livestock and prescribed fire on herbaceous biomass in the savannah woodlands of Burkina Faso, West Africa

In West Africa policies for grazing, selective tree cutting and prescribed early fire in the savannah woodlands are rarely based on long-term experimental studies. The purpose of this study was to provide scientific evidence based on field data from two case studies for an informed discussion on the effects of various management options. The main findings were by and large specific for the species, the growth form and the location. This supports the argument for devolution of management responsibility to the local level where there is such site-specific ecological knowledge. Effects of selective tree cutting (50% of basal area), livestock (1–1.4 tropical livestock unit ha−1) and prescribed early annual fire on herbaceous biomass were studied in the state forests of Laba (shallow sandy soils) and Tiogo (deep clayey soils) in the savannah woodlands in the Sudanian Zone of Burkina Faso, from 1993 to 2001. The herbaceous biomass was analysed on three levels: total herbaceous biomass, per growth form (annual and perennial grasses and forbs) and for each of the four main species in the study areas (Andropogon pseudapricus, Loudetia togoensis, Andropogon ascinodis and Andropogon gayanus). At both sites, mean total biomass during the study period was reduced by the presence of livestock while it was not significantly affected by early prescribed fire or by selective cutting. There was interaction between the three treatments at both sites. Statistically significant treatment effects were found at each site when analysing each growth form and species individually. For instance, at the growth form level, grazing reduced the biomass of annual grasses in Tiogo, perennial grasses in Laba and forbs at both sites. Site and species-specific response to grazing was found for A. ascinodis with increased biomass in Tiogo and reduced biomass of A. gayanus in Laba. Although the effect of prescribed early fire was not statistically significant the trend was the same at both sites with increased biomass of annual grasses and decreased biomass of perennial grasses. This homogenising effect of fire was statistically significant at the species level with increased biomass of the annual grass L. togoensis and decreased biomass of the perennial grass A. gayanus at both sites. Selective cutting significantly increased mean biomass of annual grasses in Tiogo whereas there was no difference in Laba.

Tillage and mulching effects on water use, root growth and yield of rainfed mustard and chickpea grown after lowland rice

Crops grown under rainfed conditions are prone to water stress, owing to rapid loss of soil moisture and development of mechanical impedance to root growth. The stress can be alleviated by enlarging rooting volume in the soil and/or by regulating the supply of soil moisture. This study reports the effects of zero, minimum and conventional tillage with and without rice straw mulch on conservation of soil moisture, root growth and yield of chickpea and mustard grown under rainfed conditions for three years (1990–91 to 1992–93) in a deep clayey soil (Typical Chromusterts). Minimum tillage, with or without straw, enhanced soil moisture conservation and moisture availability during crop growth. As a consequence, the root mass, yield components (plant stand, number of pods per plant and plant height) and grain yield increased. Availability of soil moisture during the crops growth period, maintained better plant water status. Zero tillage was superior to the other tillage practices for mustard. On the other hand, chickpea grain yield was statistically similar for zero tillage and minimum tillage. Straw mulch conserved more water in the soil profile during the early growth period compared to no mulch. Subsequent release of conserved soil water regulated proper plant water status, soil temperature, and lowered soil mechanical resistance, leading to better root growth and higher grain yield of both chick-pea and mustard in straw mulch than in no mulch plots. © 1998 Society of Chemical Industry

Quaternary sedimentation, parna, landforms, and soil landscapes of the Wagga Wagga 1 : 100 000 map sheet, south-eastern Australia

The Wagga Wagga 1 : 100 000 map sheet is on the Western Slopes of southern New South Wales. The regional topography changes from hills in the east and south-east to gently sloping rises and alluvial plains in the west. Aeolian clays (parna) form a consistent clay regolith regardless of the underlying geology in the gently sloping areas. In some alluvial plains and on some lower hill slopes, the surficial sediments contain a significant portion of reworked parna. In hilly areas, parna is poorly preserved except on some remnant ancient land surfaces, such as dissected plateaux and piedmont plains. The soil pattern in the area is well controlled by landform processes and history. On relatively steep hill slopes, locally derived materials from weathering of bedrock are usually the dominant components of the soils, and geology is the dominant factor controlling soil distribution. In contrast, the Murrumbidgee high floodplain is covered by uniform silty clay with deep clayey soils (brown/grey Dermosols). Before the mid-Holocene, the alluvium mainly comprised sands and gravels, which were reworked by wind forming sand sheets and sand mounds (source-bordering dunes) on which deep sandy soils (Rudosols) now occur. The sediments and soils on the alluvial plains of local streams vary according to their distance from the source area and the flooding frequency. Areas considered to be mantled by parna, uniform red clayey soils (haplic red Kandosols/Chromosols) occur. Although the distribution pattern of the soils is controlled by the landform evolution, the relationships between soil morphological properties and topography are not readily quantified. On the alluvial and gently sloping landforms, soil properties usually show little change even though slope gradient and slope length vary. Some soils, e.g. the Rudosols on the sand sheets, rarely show any topographic features which may indicate their presence. In limited areas, e.g. on steeper hills formed on metasedimentary rock, the soil properties vary with changes in topographic parameters (slope gradient and slope length).