Clay Research Articles

Soil liquefaction sites following the February 6, 2023, Kahramanmaraş-Türkiye earthquake sequence

AbstractSeismically induced soil liquefaction was listed as one of the major causes of damage observed in the natural and built environment during the 2023 Türkiye-Kahramanmaraş earthquake sequence. Reconnaissance field investigations were performed to collect perishable data and document the extent of damage immediately after the events. The sites with surface manifestations of seismic soil liquefaction in the form of soil ejecta, excessive foundation and ground deformations were identified and documented. The deformations were mapped, and samples from ejecta were retrieved. The ejecta samples were predominantly classified as sands with varying degrees of fines. Laboratory test results performed on liquefied soil ejecta revealed that the fines-containing liquefied ejecta samples are mostly classified as low plasticity clays (CL). Most of CL soil type ejecta were retrieved from Gölbaşı–Adıyaman region. The liquid limits of these samples varied in between 32 and 38%, their plasticity index values were estimated in the range of 16–23%. Surprisingly, two ejecta samples with plasticity indices higher than 30% were retrieved from Hatay airport, one of which was classified as high plasticity clay (CH). The majority of the fine-grained ejecta samples fall either on “Zone B: Testing Recommended” region of the Seed et al. (Keynote presentation, 26th Annual ASCE Los Angeles Geotechnical Spring Seminar, Long Beach, CA, 2003) susceptibility chart. Moreover, 12 out of 74 samples fall outside the susceptible limits defined by Seed et. These preliminary results suggest that clayey soils can produce liquefied ejecta when subjected to cyclic loading. Detailed site investigation and laboratory testing programs are ongoing to further investigate this rather unexpected response. Until their findings become available, the liquefaction susceptibility of silty-clayey soils’ mixtures is recommended to be assessed conservatively with caution.

Evaluation of an analytical method for relationship between soil hydraulic diffusivity and sorptivity under zeolite application

ABSTRACT-Zeolite is used to improve the soil hydraulic properties, i.e., soil hydraulic diffusivity (D) and sorptivity (S) that should be determined. A simple method that relates S to D was evaluated by horizontal water absorption experiment in sandy loam, loam and silty clay soils and zeolite application rates of 0, 4, 8, and 12 g kg-1 soil. Results indicated that zeolite application was not effective on the a and b values of hydraulic diffusivity function (D=aEXP(bθ), θ is the soil water content, cm3 cm-3), while maximum value of a and b in sandy loam and silty clay soils, respectively occurred by zeolite application of 8 g kg -1 soil. The values of a and b for loam soil were not influenced by zeolite application rates. Sorptivity for sandy loam soil was reduced by zeolite application rate, while minimum value of S for loam and silty clay soils occurred at zeolite application rate of 8 g kg-1 soil. It is indicated that indirect determination of S for different soil textures and zeolite application rates were closely similar to the direct determination of S. Therefore, by determination of S value by simple horizontal absorption test at two different initial soil water contents or two different absorption suction heads in tension infiltrometer the values of Ds and α for hydraulic diffusivity function (D=Dsθα) can be estimated.

Strengthening of cement blended soft clay with nano-silica particles

In recent years, Nano-technology significantly invaded the field of Geotechnical engineering, particularly in soil stabilisation techniques. Stabilisation of weak soil is envisioned to modify various soil characteristics by the addition of natural or synthetic materials into the virgin soil. In the present study, laboratory experiments were executed to investigate the influence of nano-silica particles in the consistency limits, compressive strength of the soft clay blended with cement. The results revealed that the high compressibility behaviour of soft clay modified to medium-stiff condition with fewer dosages of cement and nano-silica. The mechanism behind the strength development is verified with the previous researches as well as from Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction test (XRD) and Scanning Electron Microscopy (SEM) analysis. Based on the results, the presence of nano-silica in soft clay blended with cement has a positive effect on the behaviour of soil. This technique proves to be very economical and less detrimental to the environment.

Distorted Bounding Surface of Clay with Consideration of the Effect of Temperature on Shearing Response

Distorted Bounding Surface of Clay with Consideration of the Effect of Temperature on Shearing Response

Influence of particle size and total organic carbon on heavy metal concentrations in sediments of Lake Baringo, Kenya

Heavy metals impair water and sediment quality and thus, can cause adverse impacts on aquatic organisms especially when they exceed the recommended threshold levels. Heavy metal concentrations in water and sediments are a reflection of the anthropogenic activities on the watershed as well as the geology of the area. Metal concentrations and subsequently their bioavailability are influenced by the sediment characteristics including particle size and total organic carbon among others. This study determined the concentration of heavy metals - cadmium (Cd), copper (Cu) mercury (Hg) and lead (Pb) in the sediments in relation to grain size and total organic carbon in Lake Baringo. Samples were collected from five sites using a grab sampler and analyzed for total heavy metals using AAS. Particle size classification was done using the sieve method, while organic carbon (OC) was estimated using the Loss on Ignition (L.O.I) method. One way ANOVA revealed significant difference in mean Cu concentrations amongst the sampling sites at P<0.05 (F (4, 14) =6.945 p=0.01). However, there was no significant differences in the levels of Cd and Hg, that is, F (4, 14) =0.03, p= 1.0 and F (4, 14) = 0.36 p=0.83 respectively. However, there was no significant difference in the levels of Cd and Hg. Sites with higher percentages of silt and clay recorded a higher concentration of Cd and Cu as well as percentage of TOC. The results indicated the pollution of the lake by heavy metals presented an ecological and a human health concern requiring monitoring. Key words: Sediment quality, heavy metals, particle size, total organic carbon.

Traditional production and quality perception of grilled pork consumed in Benin

Traditional grilled pork is a well appreciated ready-to-eat on the spot or takeaway food produced in Benin. This study, realized via field investigation, aimed to provide a better understanding of the traditional grilled pork production in Benin, for future improvement of the process and product quality for urban dwellers. The study showed most processors were men (85.6%), illustrating the particularity of this activity in the country where most street food vendors are women. They were also young (≤ 40 years - 63.9%), mainly from Goun and Fon sociocultural groups (59.5%), illiterate or primary school educated (72.3%). Indigenous pig breeds were preferred for processing (93.6%). Bristles elimination of the pig was carried out either by scalding or singeing. Among the eight grilling equipment recorded, vertical barrel grill was the most commonly used (46.8%) followed by locally made clay grills (28.7%). Wood (62.8%) and charcoal (37.2%) were the most used fuel for grilling. The diversity of equipment and methods used in traditional grilled pork production could be a source of quality variability of grilled pork in Benin. The texture was considered the suitable criteria to appreciate precooked (40.5%) and grilled pork (72.3%), while colour was used to appreciate fresh pork quality (53.2%). Key words: Pig meat, traditional grill, fuel, singeing, quality.

Field test on pile tip resistance of closed-end jacked pipe pile penetrating into layered foundation

In the layered soil foundation mainly composed of silty clay and silty clay, test piles with full cross-section pressure sensors installed at the end of piles are used to continuously and intensively collect pile tip resistances in the whole penetrating process with high density. throughout the entire process. According to the pile tip resistance curves of multiple penetration strokes, the change stage of the initial penetration of the pile tip resistance into the soil layer and the change stage of continuous penetration into the same soil layer are defined, which are divided into linear steep increase segments, nonlinear ramp segments, and platform segments, nonlinear slow-down section, linear steep drop section. When the pile end continuously penetrates through the interface of multiple soil layers, the change stage of the pile end resistance lacks a linear steep increase section compared with the initial penetration soil layer. The initial value of the steep drop of the previous stroke is close to the final value of the steep rise of the latter stroke, which can reflect the limit of the elastic compression of the soil, and is calculated by the average value of Qc, and is used as the pile foundation design. The pile tip resistance curve during the pile sinking process is similar to the static penetrating Qc curve. The maximum tip resistance of every layer in the layered soil is linear with the Qc value of the static penetrating probe and the average number of standard penetrations. Analysis of this situation found that the residual end-resistance after restoration was linearly related to the Qc value of cone penetration test(CPT) and the N value of standard penetration test(SPT). The fitting formula of elastic limit pile end resistance and ultimate pile tip resistance and residual tip resistance are put forward; and the fitting formula of ultimate pile tip resistance is more accurate than that of empirical parameter method, static cone penetration method and limit equilibrium theory.

Preservation of erniettomorph fossils in clay-rich siliciclastic deposits from the Ediacaran Wood Canyon Formation, Nevada: Ediacaran preservation in sandstone beds

Author(s): Hall, JG; Smith, EF; Tamura, N; Fakra, SC; Bosak, T | Abstract: Three-dimensionally preserved Ediacaran fossils occur globally within sandstone beds. Sandy siliciclastic deposits of the Ediacaran Wood Canyon Formation (WCF) in the Montgomery Mountains, Nevada, contain two fossil morphologies with similar shapes and sizes: one exhibits mm-scale ridges and a distinct lower boundary and the other is devoid of these diagnostic features. We interpret these as taphomorphs of erniettomorphs, soft-bodied organisms with uncertain taxonomic affinities. We explore the cast-and-mould preservation of both taphomorphs by petrography, Raman spectroscopy, X-ray fluorescence microprobe and X-ray diffraction. All fossils and the surrounding sedimentary matrix contain quartz grains, iron-rich chlorite and muscovite. The ridged fossils contain about 70% larger quartz grains compared to the ridgeless taphomorph, indicating a lower abundance of clay minerals in the ridged fossil. Chlorite and muscovite likely originated from smectite and kaolinite precursors that underwent lower greenschist facies metamorphism. Kaolinite and smectite are inferred to have been abundant in sediments around the ridged fossil, which enabled the preservation of a continuous, distinct, clay- and kerogen-rich bottom boundary. The prevalence of quartz in the ridged fossils of the WCF and in erniettomorphs from other localities also suggests a role for this mineral in three-dimensional preservation of erniettomorphs in sandstone and siltstone deposits.

Performance evaluation of β-glucan treated lean clay and efficacy of its choice as a sustainable alternative for ground improvement

The choice of eco-friendly materials for ground improvement is a necessary way forward for sustainable development. Adapting naturally available biopolymers will render the process of soil stabilization carbon neutral. An attempt has been made to use β-glucan a natural biopolymer for the stabilization of lean clay as a sustainable alternative with specific emphasis on comprehending the effect of confining stresses on lean clay through triaxial compression tests. A sequence of laboratory experiments was performed to examine the various physical and mechanical characteristics of β-glucan treated soil (BGTS). Micro-analysis through micrographs were used to understand the strengthening mechanism. Results of the study show that the deviatoric stress of 2% BGTS is 12 times higher than untreated soil (UTS). The micrographs from Scanning Electron Microscopy (SEM) and the results of the Nitrogen-based Brunauer Emmett Teller (N2-BET) analysis confirm the formation of new cementitious fibres and hydrogels within the soil matrix that tends to weld soil particles and reduce the pore spaces leading to an increase in strength. Hydraulic conductivity (HC) and compressibility reduced significantly with the biopolymer content and curing period. Results emphases that β-glucan is an efficient and sustainable alternative to the traditional stabilizers like cement, lime or bitumen.

Interactions of Soil and Vegetation Determine Habitat for Southeastern Pocket Gopher (Geomys pinetis)

Pocket gophers (Geomyidae) require soils amenable to burrowing and vegetation communities that provide adequate foods. We examined the interplay of soil texture and vegetation structure in determining site occupancy of the southeastern pocket gopher (Geomys pinetis), a species of conservation concern throughout its range. Using a case-control sampling design, we compared vegetation structure and soil texture between occupied and unoccupied sites in southeastern Alabama. All occupied sites had soil clay content ≤8.05% at 0–20 cm depth. In logistic regression modeling, clay content had overwhelming support as the most important single habitat variable distinguishing occupied from unoccupied sites. Based on soil results, we focused our examination of vegetation structure on the subset of our sites with <10% clay at 0–20 cm depth. Relative odds of occupancy were highest at intermediate levels of canopy cover; however, canopy cover at occupied sites ranged widely. Compared to unoccupied sites, occupied sites contained less midstory cover and greater ground cover of graminoids and shrubs. Our results demonstrate that although vegetation structure is important in determining site suitability, soil texture may be an overriding constraint limiting potential habitat for this species. Conservation actions for southeastern pocket gophers such as habitat restoration and population translocations should ensure that target sites have suitable low-clay soils.

Effect of water content on near-pile silt deformation during pile driving using PIV technology

Piles are widely used in structural foundations of engineering projects. However, the deformation of the soil around the pile caused by driving process has an adverse effect on adjacent existing underground buildings. Many previous studies have addressed related problems in sand and saturated clay. Nevertheless, the failure mechanism of pile driving in unsaturated soil remains scarcely reported, and this issue needs to be studied. In this study, a modeling test system based on particle image velocimetry (PIV) was developed for studying deformation characteristics of pile driving in unsaturated silt with different water contents. Meanwhile, a series of direct shear tests and soil-water characteristic curve (SWCC) tests also were conducted. The test results show that the displacement field shows an apparent squeezing effect under the pile end. The installation pressure and displacement field characteristics are sensitive to the water content. The installation pressure is the largest and the total displacement field is the smallest, for specimens compacted at water content of 11.5%. These observations can be reasonably interpreted according to the relevant unsaturated silt theory derived from SWCC tests and direct shear tests. The variation characteristics of the soil displacement field reflect the macroscopic mechanical properties of the soil around the pile.

Revealing a Significant Center of Sedge Diversity: Carex (Cyperaceae) of Jackson County, Alabama, U.S.A.

Jackson County is the northeasternmost county of Alabama, U.S.A., and falls entirely in the southern portion of the Appalachian Plateaus physiographic province. Based on multiple years of fieldwork, herbarium work, and review of online (digitized) specimens, this study presents the diversity, habitats, biogeography, and conservation status of Carex in Jackson County. We document 90 Carex taxa from Jackson County by voucher specimens deposited in multiple herbaria. This value exceeds the number of taxa known from other, similar-sized regions in the southern part of the Appalachian Plateaus. Carex albicans var. emmonsii is a new state record and is known in Alabama only from Jackson County. We encountered high numbers of misidentifications among specimens collected prior to this study and exclude nine taxa previously reported from Jackson County that are based on misidentifications. Carex plants grow in a great number of habitats in Jackson County, with two hosting the greatest number of taxa: mature, wet-mesic, deciduous, floodplain forests on clays and clay loams; and mature, mesic, calcium-rich, deciduous, upland forests on loams. Jackson County is a nexus for both southeastern endemics and taxa occurring at or near their southern limits. Thirteen of the Carex taxa are rare in Alabama and likely of conservation concern in the state. This study contributes fundamental knowledge that makes sedge diversity, ecology, geography, and conservation better known, and is especially important for revealing a significant center of Carex diversity in North America.

Estudo da potencialidade do concentrado de caulinita para aplicação cosmética

As máscaras argilosas são apontadas como as mais antigas preparações cosméticas utilizadas no tratamento de beleza em função da sua vasta gama de propriedades, logo, sua aplicabilidade na área cosmética depende primordialmente da composição química e mineralógica. Essa variabilidade na composição reforça a necessidade de se fazer estudos que proporcionam um maior entendimento dos compostos, bem como as diferentes possibilidades de aplicações. Objetivou-se caracterizar o concentrado de caulinita proveniente dos estados da Paraíba e do Rio Grande do Norte a fim de realizar um estudo comparativo com os parâmetros definidos por empresas do segmento. Para a realização da pesquisa foram coletadas de três diferentes unidades de beneficiamento de caulim, se-se ensaios laboratoriais seguindo metodologias específicas para o segmento cosmético e, posteriormente, comparações com especificações em laudos técnicos. Os ensaios foram: determinação de umidade, ensaio de peneiramento, determinação de pH, ensaio de absorção e ensaio colorimétrico qualitativo. Os resultados obtidos evidenciaram os valores de umidade para todas como em decorrência do processo de beneficiamento, enquanto nenhum ensaio de peneiramento não houve amostra com comportamento fora do limite estabelecido. Como forma de lucro levemente ácido com A2 e A3 valores satisfatórios, já no ensaio de absorção de oleosidade como A1 e A2 atenderam aos limites de variação.

Geri Dönüştürülmüş Beton Agregasının Düşük Plastisiteli Bir Kilin Mekanik Özelliklerine Etkisi

Bu çalışmada, beton dayanımını belirlemek amacı ile test edilmiş olan beton numunesi atıklarının ufalanması ile elde edilmiş olan geri dönüştürülmüş beton agregalarının (GDA) yol ve dolgu yapımında alt temel malzemesi olarak kullanımı üzerine deneysel bir araştırma yapılmıştır. Beton numunesi atıkları laboratuvar ortamında el yordamı ile kırılıp elenmek sureti ile deneyler için gerekli boyutlara indirilmiştir. Bölge civarında temin edilen killi zemin, dolgu yapımında kullanılacak alt temel malzemesi olarak seçilmiştir. 425 mikron boyutundan elenerek (40 nolu elek) hazırlanmış olan GDA, alt temel zemini ile %5, %10 ve %15 oranlarında karıştırılmak sureti ile farklı karışım oranlarında örnekler hazırlanmıştır. GDA nın killi zeminin mekanik özelliklerine etkisinin belirlenmesi için hazırlanan karışımlar üzerinde; standart Proctor, serbest basınç dayanımı (UCS) ve Kaliforniya taşıma oranı (CBR) şeklinde bir seri deney gerçekleştirilmiştir. Deneysel çalışmanın sonuçlarına göre GDA düşük plastisiteli killi zeminin mekanik özelliklerini iyileştirmektedir.

Assessment of selected soil physicochemical properties on different land-use systems and landscape positions at Hamesa watershed, Wolayita zone, Southern Ethiopia

The investigation was undertaken at Hamesa watershed of Wolayita Zone with the aim to assess the consequences of land-use systems and topography on the physical and chemical properties of selected soils. Surface soil samples taken at 0-15 and 15-30 cm depths from three land-use systems (enset, grassland and maize fields) were collected under three slope positions (upper, middle and lower). Both the clay and bulk density increased with depth, while total nitrogen (N), OC, available P and micro-nutrients (Fe, Zn, Mn, and Cu) decreased. On the landscape positions, increase in exchangeable Ca and K, pH, bulk density and available Mn down the slope was observed; whereas total N, OC, available P and available Fe showed decreasing trend down the slope. At 0-15 cm soil depth, grassland soils exhibited higher bulk density and lower porosity as a result of livestock movement which was compacted. Grasslands had higher OC and TN compared to the other two land-use systems, due to the accumulation of humus in the root system in the grassland. Application of household refuses and manure contribute to increasing available P, TN, Zn, Ca and K contents in enset farmland. On the contrary, maize land use had lower CEC, K, PBS, Mg, TN and OC, which might be due to crop removal, erosion phenomena, and excessive tillage activities. These results suggest that for sustainable crop production, proper management practices should be in place by considering different slope positions and land-use systems. Key words: Land use system, slope position, physical, chemical soil properties.

Application of Nanotechnology in Oil and Gas Industry: Synthesis and Characterization of Organo-modified Bentonite from Boane Deposit and its Application in Produced Water Treatment

Ca-bentonite sample from Boane region, Maputo Province, Mozambique exhibiting a white colour was organo-modified and subsequently evaluated for uses as an adsorbent for the treatment of produced water from a natural gas production platform. The clay was subjected to organo-modification through ion-exchange reaction by cationic surfactants namely benzalkonium chloride and cetrimonium bromide. The organophilization process altered the natural hydrophilic character to hydrophobic. The effectiveness of the ion-exchange procedure was revealed by XRD patterns, wherein the main Ca-MMT d001 peak changed from 1.520 nm to 1.960 nm when the concentration of cetrimonium bromide used for organo-modification varied from 50 to 100 meq and from 1.520 to 1.830 nm when a fixed concentration of benzalkonium chloride was used. Wastewater treatment performance evaluation of synthesized products showed that the physico-chemical and bacteriological properties improved significantly, showing clearly that Boane bentonite has enormous potential to be applied as an adsorbent material for produced water treatment.

Thermal Performance of Phase Change Material Wallboard with Typical Structure: Artificial Controlled Condition Experimental Investigation

Phase change material (PCM) integrated with building envelopes could enhance thermal storage performance of building envelopes significantly. Due to the variable physical property of PCM, the thermal performance of PCM envelopes is different from traditional envelopes such as clay brick and concrete wall. In the present paper, the thermal performance of PCM envelopes are experimentally investigated in an artificial climate chamber. The experimental PCM wallboard is made by PCM layer, concrete layer and insulation layer, which could reflect the real envelopes structure in typical office buildings in Western China. The thermal performance of the wallboard with different material layer locations is compared, and the thickness of PCM layer is optimized. During the experiments, the PCM wallboard is under double-sides heat effect, including periodic outdoor air temperature fluctuation and indoor heat source. Two indicators named thermal inertia index and coefficient of heat accumulation of interior surface are introduced as the key parameters to evaluate the thermal storage performance of the PCM envelopes. The results show that, under double-sides periodic thermal effect, the indoor air temperature is mainly affected by the coefficient of heat accumulation of interior surface of the PCM wallboard. However, the increment of the thermal inertia index of the whole wallboard has little influence on the indoor thermal environment under double-sides periodic thermal effect.

Geomechanical properties of synthesised clayey rocks in process of high-pressure compression and consolidation

Oil and natural gas reserves have been recognised abundantly in clayey rich rock formations in deep costal reservoirs. It is necessary to understand the sedimentary history of those reservoir rocks to well explore these natural resources. This work designs a group of laboratory experiments to mimic the physical process of the sedimentary clay-rich rock formation. It presents characterisation results of the physical properties of the artificial clayey rocks synthesized from illite clay, quartz sand and brine water by high-pressure consolidation tests. Special focus is given on the effects of illite clay content and high-stress consolidation on the physical properties. Multi-step loaded consolidation experiments were carried out with stress up to 35 MPa on mixtures constituting of the illite clay, quartz sand and brine water with five initial illite clay contents (w=85%, 70%, 55%, 40% and 25%). Compressibility and void ratio were characterised throughout the physical compaction process of the mixtures constituting of five illite clay contents and their water permeability was measured as well. Results show that the applied stress induces a great reduction of clayey rock void ratio. Illite clay contents has a significant influence on the compressibility, void ratio and the permeability of the physically synthesized clayey rocks. There is a critical illite clay content w=70% that induces the minimum void ratio in the physically synthesised clayey rocks. The SEM study indicates, in the high-pressure synthesised clayey rocks with high illite clay contents, the illite clay minerals are located in layers and serve as the material matrix, and the quartz minerals fill in the inter-mineral pores or are embedded in the illite clay matrix. The arrangements of the minerals in microscale originate the structural anisotropy of the high-pressure synthesised clayey rock. The test findings can give an intuitive physical understanding of the deep-buried clayey rock basins in energy reservoirs.

Effects of Root-Knot Nematode Inoculums Densities on Morphological and Phytochemical Analysis of Selected Horse Gram Germplasm

Root-knot nematodes (Meloidogyne incognita; RKN) are important constraints on agricultural crops worldwide. Horse gram is a vulnerable pulse crop from the agriculture revolution exceptionally in southern India. This study intended to assess the resistance of four Horse gram accessions IC-1536, IC-1572, IC-1451 and IC-1115 selected from 100 accessions based on the morphological and biochemical scrutiny. Individual seedlings were transferred in the clay pots packed with sterile soil and inoculated with three doses (25, 50 and 100) of second stage juveniles of M. incognita. All nematode inoculums densities influenced the shoot length of plants, flowering and yield. The level of amino acid, proline, protein, total phenol and flavonoids contents were increased while carbohydrate and starch contents were decreased in all the varieties compared to the 15th day after inoculation. It is pointed out that M. incognita has not only impaired the plant growth but also biochemical parameters such as chlorophyll pigments, primary and secondary metabolites.

Settlement analysis of pile cap with normal and under-reamed piles

The use of pile foundations has become more popular in recent years, as the combined action of the pile cap and the piles can increase the bearing capacity, reduce settlement, and the piles can be arranged so as to reduce differential deflection in the pile cap. Piles are relatively long, slender members that transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock strata having a high bearing capacity. In this study analysis of pile cap with considering different parameters like depth of the pile cap, width and breadth of the pile cap, type of piles and different types of soil which affect the behaviour of pile cap foundation is carried out by using Finite Element Software ANSYS. For understanding the settlement behaviour of pile cap foundation, parametric studies have been carried out in four types of clay by varying pile cap dimensions with two types of piles namely normal and under-reamed piles for different group of piles. Furthermore, the analysis results of settlement and stress values for the pile cap with normal and under-reamed piles are compared. From the study it can be concluded that settlement values of pile cap with under-reamed pile are less than the settlements of pile cap with normal pile. It means that the ultimate load bearing capacity of pile cap with under-reamed piles are greater than the pile cap with normal piles.