Spreading Ground Research Articles

Critical liquefied soil thickness for response patterns of piles in inclined liquefied ground overlain by nonliquefied crust

AbstractLateral spreading has historically caused extensive pile failure in liquefaction‐prone areas during strong earthquakes. A critical design scenario involves piles embedded in lateral spreading ground composed of a nonliquefied soil crust overlying a liquefied layer; it is critical because both layers can exert loads on the piles. Different thicknesses of the liquefied soil and the upper nonliquefied crust may engender different pile response patterns. Accordingly, to investigate factors influencing the lateral responses of a single pile embedded in liquefied ground with a nonliquefied crust, we conduct parametric analyses. The effects of liquefied and nonliquefied soil thicknesses are analyzed first, followed by those of pile‐head rotational restraint, pile diameter, and lateral spreading displacement. We observe two main pile response patterns for various liquefied soil thicknesses. The ground can be categorized into thin or thick liquefied ground depending on whether its liquefied soil thickness is less or greater than a critical value, namely, critical liquefied soil thickness; this critical thickness is dependent on the pile‐head rotational restraint, pile diameter, and lateral spreading displacement. The difference in the patterns stems from the varying roles of the upper nonliquefied soil layer during lateral spreading. For the thin liquefied ground, the nonliquefied layer contributes to adding lateral spreading force; therefore, the displacement, moment, and shear force responses of the pile increase with the nonliquefied soil thickness. However, for the thick liquefied ground, the nonliquefied layer provides resistance to lateral spreading; therefore, the maximum displacement, moment, and shear force of the pile initially decreases and then gradually increases with the nonliquefied soil thickness.

Fluvial geomorphic factors affecting liquefaction-induced lateral spreading

Liquefaction-induced lateral displacements represent a major geohazard in earthquake-prone regions, yet the uncertainty associated with their prediction remains notoriously high. Documented observations after recent earthquakes provide evidence that depositional environment-specific geologic conditions play a crucial role in liquefaction susceptibility, and in the severity and spatial extent of liquefaction-induced ground deformations. However, this evidence is largely qualitative in nature, which limits the potential to incorporate the effects of depositional processes and environments in the next generation of lateral spreading predictive models. This study provides a framework to quantitatively assess the relationship between depositional environment-specific geologic factors and lateral spreading by means of simple fluvial geomorphic facies models, geotechnical engineering data (e.g. Cone Penetration Test data), and geospatial analytics. Three hypotheses are introduced and tested using lateral spreading ground deformations observed following the 2011 Christchurch earthquake along the Avon and Heathcote rivers in New Zealand. The results from this study indicate that the presence of an active (i.e. with active sediment deposition) compared to inactive (e.g. abandoned) channels is the most important fluvial geomorphologic variable out of the three tested. The other two are associated with the location relative to the meander bend position, including location within the point bar (inside) or the cut bank (outside), and upstream versus downstream within a given point bar. Findings from this study show that more lateral spreading occurs within point bars, and upstream (within a given point bar) in simple meander bends. However, the presence of geomorphic complexities (e.g. cut banks connected to an incised channel or tributary and/or channel confinement) can challenge the unbiased quantification of the contribution of a single geomorphic variable to the observed lateral displacements. These findings can be applied to other fluvial environments outside of New Zealand, and the proposed framework can be implemented for other non-fluvial depositional settings.

Soil-pile-quay wall interaction in liquefaction-induced lateral spreading ground

Earthquake-induced soil liquefaction and lateral spreading often causes damage to pile foundations of quays and offshore structures. In this study, the soil-pile-quay wall interaction in liquefaction-induced lateral spreading ground was analyzed from three perspectives—experimental investigation, numerical simulation, and parametric analysis. A large-scale (1 g acceleration) shake-table test was conducted on a 2 × 2 pile group behind a quay wall, and described in terms of sensor arrangement, model configuration, and test results. The test resulted in phenomena such as the quay wall overturning to the water side, and ground settlement. A 2D (two-dimensional) nonlinear FE (finite element) model of a coupled dynamic soil-water system, which considered soil-pile-quay wall interactions, was validated using the experimental data. Based on the validated model, a parametric study was conducted to illuminate the effects of the pile head fixing conditions, pile stiffness, superstructure mass, permeability coefficient, and acceleration. The results indicated that these parameters had a significant influence on the soil-pile-quay wall interaction in the liquefaction-induced lateral spreading ground. Investigating the effects of each of the five parameters on the dynamic performance of pile foundations in this study has guiding implications for tests and numerical simulations.

Tracking antibiotic resistance through the environment near a biosolid spreading ground: Resistome changes, distribution, and metal(loid) co-selection

The application of urban wastewater treatment plants (WWTPs) products to agricultural lands has contributed to the rising level of antibiotic resistance and drawn a critical public health concern. It has not been thoroughly investigated at which spatial scales a biosolid applied area as a potentially predominant source affects surrounding soil resistomes. This study investigated distribution and impact of WWTP biosolids treated with anaerobic digestion on an agricultural area. Heterotrophic plate counts (HPCs) and quantitative polymerase chain reaction (qPCR) were performed for detection of selected antibiotic-resistant bacteria (ARB), selected antibiotic resistance genes (ARGs), intI1 genes, and 16S rRNA genes. Biosolid samples contained significantly higher levels of selected ARGs than the raw agricultural soils (p < 0.05). The average relative abundances of intI1, sul1, blaSHV, and ermB genes were significantly higher in biosolid-amended soils than nearby agricultural soils (p < 0.05). Spatial interpolation analysis of relative gene abundances of intI1, sul1, sul2, and tetW across the studied area further indicated directional trends towards the northwest and southeast directions, highlighting possible airborne spread. Concentrations of Co, Cu, Ni, and Fe were found to be significantly and positively correlated with relative abundances of intI1, sul1, and tetW genes (p < 0.05). The resistance ratios of culturable antibiotic-resistant bacteria in agricultural soils with biosolid amendments were generally identical to those without biosolid amendments. This study will advance the understanding of the antibiotic resistome in agricultural soils impacted by long-term waste reuse and inform the evaluation strategies for future biosolids application and management.

Relative benthic disturbances of conventional and novel otter boards and ground gears

A benthic trawl’s substrate contact (e.g. spreading mechanisms (i.e. otter boards) and ground gears) determines both its catching efficiency and the extent of perceived habitat impacts. The potential for mitigating habitat impacts was investigated here via the novel ‘batwing’ otter board and ‘soft-brush’ ground gear. A purpose-built testing assembly towed treatments across three artificial habitat types with incrementally greater detachment thresholds (~ 8, 32 and 56 N), and the batwing and soft-brush were alternately compared against a conventional flat-rectangular otter board and three chain ground gears (6-, 8- and 10-mm diameter link), respectively. Overall, during 48 alternate deployments, the batwing removed up to 61% fewer of all habitats than the flat-rectangular otter board. By comparison, during 42 alternate replicates, the soft-brush ground gear failed to displace any habitat, while all three chain ground gears similarly removed between 3 and 5% of the two least resistant habitats (irrespective of position). The results imply the perceived impacts of penaeid trawls across sensitive areas can be reduced via simple modifications to spreading mechanisms and ground gears, along with appropriate spatio-temporal regulation. This study represents a unique approach to understanding the relative differences in impacts between ground gears and commercial-sized otter boards under controlled conditions.

Performance of X-shaped and circular pile-improved ground subject to liquefaction-induced lateral spreading

Liquefaction-induced lateral spreading has caused severe damage and significant financial losses in major earthquakes distributed globally. Groups of piling installed in liquefaction- and lateral spreading-susceptible ground has been proven to be effective in reducing lateral displacements, but further investigation into the soil-structure interactions is required to elucidate the mechanisms for mitigation of displacement. Further, it is hypothesized that cross-, or X-shaped, piling may provide improved restraint on lateral flow deformations due the destructive interference of flow imposed by their cross-section. In this paper, the effectiveness of groups of X-shaped and circular piles to mitigate lateral spreading ground was investigated to improve the understanding of the mechanisms for improvement. Shake table tests were carried out to examine and compare the efficacy and efficiency of X-shaped and circular pile groups. Design parameters including the pile arrangement (square vs. triangular spacing) and orientation (X vs. +) of the X-shaped piling were also taken into consideration. The results demonstrate that the X-shaped pile groups can significantly reduce the lateral displacement and the areal extent of liquefied sand flow as compared to the unimproved and circular pile-improved ground, and that the spacing and orientation play a critical role in the deformation response. These findings will help inform the design of pile-improved ground as well as the design of structural piling adjacent to submerged, liquefiable slopes.

Efficient Finite-Element Model for Seismic Response Estimation of Piles and Soils in Liquefied and Laterally Spreading Ground Considering Shear Localization

AbstractA key challenge for estimating seismic response of piles and soils in liquefied and laterally spreading ground is the efficient prediction of local loosening phenomenon (shear localization) at the interlayer between the liquefied loose sand and the overburden crust. To this end, a simplified finite-element (FE) model was developed. In the soil model, a soft interlayer element with a thickness and corresponding low reference shear modulus was developed to represent the shear localization phenomenon. The proposed FE models were then used to simulate centrifuge tests of a single pile, a two-pile group, and a six-pile group in sloping liquefiable profiles that lead to lateral spreading. Predicted results of the shear-localization-induced soil lateral spreading displacement, as well as the structural response, agree reasonably well with the test records, indicating that the proposed FE model is capable of approximating the seismic responses of soil and piles in liquefied and laterally spreading ground....

Effects of liquefaction-induced large lateral ground deformation on pile foundations

The pile-soil system interaction computational model in liquefaction-induced lateral spreading ground was established by the finite difference numerical method. Considering an elastic-plastic subgrade reaction method, numerical methods involving finite difference approach of pile in liquefaction-induced lateral spreading ground were derived and implemented into a finite difference program. Based on the monotonic loading tests on saturated sand after liquefaction, the liquefaction lateral deformation of the site where group piles are located was predicted. The effects of lateral ground deformation after liquefaction on a group of pile foundations were studied using the finite difference program mentioned above, and the failure mechanism of group piles in liquefaction-induced lateral spreading ground was obtained. The applicability of the program was preliminarily verified. The results show that the bending moments at the interfaces between liquefied and non-liquefied soil layers are larger than those at the pile’s top when the pile’s top is embedded. The value of the additional static bending moment is larger than the peak dynamic bending moment during the earthquake, so in the pile foundation design, more than the superstructure’s dynamics should be considered and the effect of lateral ground deformation on pile foundations cannot be neglected.

FEM Analysis of Dynamic Soil-Pile-Structure Interaction in Liquefied and Laterally Spreading Ground

A two-dimensional nonlinear dynamic finite element (FE) model was developed and calibrated against dynamic centrifuge tests to study the behavior of soil-pile-structure systems in liquefied and laterally spreading ground during earthquakes. The centrifuge models included a simple structure supported on pile group. The soil profiles consisted of a gently sloping clay crust over liquefiable sand over dense sand. The FE model used an effective stress pressure dependent plasticity model for liquefiable soil and a total stress pressure independent plasticity model for clay, beam column elements for piles and structure, and interface springs that couple with the soil mesh for soil-structure interaction. The FE model was evaluated against recorded data for eight cases with same set of baseline parameters. Comparisons between analyses and experiments showed that the FE model was able to approximate the soil and structural responses and reproduce the lateral loads and bending moments on the piles reasonably well.

Analysis of Three Bridges That Exhibited Various Performance Levels in Liquefied and Laterally Spreading Ground

Three bridges supported on deep foundations that exhibited various performance levels in liquefied and laterally spreading ground are analyzed using a beam on nonlinear Winkler foundation method. The performance levels were (1) no measurable foundation deformation, (2) moderate damage, and (3) collapse. Analyses are first performed using the best available information regarding ground motions and free-field lateral spreading surface displacements. Predictions closely match observations when the inputs are well known. The cases are subsequently reanalyzed using a probabilistic forward prediction that incorporates uncertainty in the ground motion, liquefaction triggering evaluation, lateral spreading surface displacement, and structural response. Significant differences in lateral spreading displacements estimated by different methods introduced significant dispersion into predictions of structural response for cases of poor performance in which the piles moved with the spreading soil but had little influence for cases with good performance where the liquefied soil spread around a stiff pile foundation.

Ground Movement and Strains from Airphoto Measurements in Avonside Caused by 2010 Darfield Earthquake

In this work ground failure following the 2010 Darfield earthquake in Canterbury, NZ was studied. Lateral spreading and horizontal ground strains were analyzed in an area near the Central Business District of Christchurch city. The Avon river runs through the middle of the study area and includes natural, filled and artificially cut stream bed stretches. Lateral displacement vectors from photogrammetric data were interpolated and used to produce ground strains. Large compressive and tensile strains were identified. Natural point bars were found to correlate closely with tensile strains. Natural stream bed (filled and existing) was found to closely correlate with compressive strains. Vector magnitude values of lateral displacements were found to correlate with water supply pipe repair rates (R2 = 0.42). However, ground strains did not correlate with lateral displacements, water supply pipe repair rates or settlements from the photogrammetric data. Therefore, it may be concluded that ground strains have limited use in the indication of potential repair rates and do not directly predict settlement. However, ground strains were observed as useful in identifying paleo-geomorphology of the area in general and changing soil density profiles in particular.

Fragility Functions for Bridges in Liquefaction-Induced Lateral Spreads

Fragility functions are generated for bridges in liquefied and laterally spreading ground using equivalent static global nonlinear finite element analyses. Bridges are classified based on structural configurations and vintage. Probability density functions are assigned to both structural and geotechnical properties of bridges. Nonlinear equivalent static analyses are conducted with inputs sampled randomly using the Monte Carlo simulation method. Cumulative distribution functions are fitted to the simulated data, and define the probability of exceeding various engineering demand parameters (pier column curvature ductility, pile cap displacement, abutment displacement, etc.) conditioned on the maximum free-field lateral spreading ground surface displacement. Correlations among EDPs are presented to facilitate risk assessment based on a vector of EDPs. The derived fragility functions, combined with seismic hazard analysis, liquefaction potential, and lateral spreading estimation, are useful in the context of performance-based earthquake engineering and risk assessment of current bridge inventory in California.

Static Pushover Analyses of Pile Groups in Liquefied and Laterally Spreading Ground in Centrifuge Tests

Monotonic, static beam on nonlinear Winkler foundation (BNWF) methods are used to analyze a suite of dynamic centrifuge model tests involving pile group foundations embedded in a mildly sloping soil profile that develops liquefaction-induced lateral spreading during earthquake shaking. A single set of recommended design guidelines was used for a baseline set of analyses. When lateral spreading demands were modeled by imposing free-field soil displacements to the free ends of the soil springs (BNWF_SD), bending moments were predicted within -8% to +69 (16th to 84th percentile values) and pile cap displacements were predicted within -6 to +38%, with the accuracy being similar for small, medium, and large motions. When lateral spreading demands were modeled by imposing limit pressures directly to the pile nodes (BNWF_LP), bending moments and cap displacements were greatly overpredicted for small and medium motions where the lateral spreading displacements were not large enough to mobilize limit pressures, and pile cap displacements were greatly underpredicted for large motions. The effects of various parameter relations and alternative design guidelines on the accuracy of the BNWF analyses were evaluated. Sources of bias and dispersion in the BNWF predictions and the issues of greatest importance to foundation performance are discussed. The results of these comparisons indicate that certain guidelines and assumptions that are common in engineering design can produce significantly conservative or unconservative BNWF predictions, whereas the guidelines recommended herein can produce reasonably accurate predictions.

The taxonomy, ecology and conservation status of the Golden-rayed Blue: a threatened butterfly endemic to western Victoria, Australia

The Golden-rayed Blue, Candalides noelkeri sp. nov. (Lepidoptera: Lycaenidae), from the Wimmera of western Victoria, Australia, is described and illustrated. The male and female genitalia and immature stages are figured, described and compared with those of Candalides heathi and C. xanthospilos. Candalides noelkeri sp. nov. is placed in the C. xanthospilos species-group, being most closely allied to and allopatric with C. heathi. It is predominantly univoltine, with adults usually present from late November to early February. However, it has a facultative pupal diapause that gives rise to a partial overlapping second generation in mid-summer. The species is ecologically specialized, monophagous and has a narrow geographical range, currently known only from two localities in a restricted area near Natimuk. Within this limited area it is restricted to flood plains bordering natural salt-lakes where the larval food plant, a prostrate form of Myoporum parvifolium (Myoporaceae), grows as a low spreading ground cover plant. Morphological and geological evidence suggest a recent (late Pleistocene) allopatric speciation event between C. noelkeri sp. nov. and C. heathi. The small, peripheral spatial distribution of C. noelkeri sp. nov. implies that differentiation has been achieved by the founder effect, either through peripheral isolates speciation (peripatric speciation) or postspeciation dispersal, possibly as a result of a barrier created by the volcanic plains in western Victoria. Available information indicates that C. noelkeri sp. nov., Victoria's only endemic species of butterfly, is facing a high risk of extinction and accordingly its conservation status should be considered as Endangered. The most serious threat at the type locality is habitat change or succession caused by invasion of Melaleuca halmaturorum, which is creating a dense shaded paperbark forest that is reducing both the preferred open sunny microhabitat and the extent of the larval food plant. Recognition of C. noelkeri sp. nov. as a flagship taxon is likely to enhance the conservation of biodiversity in remnant flood plain/salt-lake ecosystems of temperate south-eastern Australia.

Geophysical investigation of proposed sites for artificial recharge in Northern Oman

Abstract Sites in the interior of the Sultanate of Oman have been considered for the construction of recharge dams for temporarily impounding flood flows from the Northern Oman Mountains. Impounded water would be discharged under control to infiltrate into downstream aquifers. Four geophysical methods were applied to characterization of the spreading ground downstream of these sites and to guide drilling of test bores. The main aquifers occur in permeable zones at the base of the alluvium and in the upper, weathered, bedrock. The alluvium is variably cemented and clay rich, and behaves as a confining layer between the shallow, unconsolidated surface infiltration zone and the aquifer. The thickness of the upper unconsolidated layer of boulders and gravels was most accurately mapped with seismic refraction or vertical electrical sounding (VES). These methods were slow to apply in the arid, bouldery ground conditions and surveying was in places constrained by the wadi walls. Gravity survey, with control provided by VES, was a rapid method of profiling the total thickness of alluvium and weathered zone overlying the denser and more resistive unweathered ophiolite bedrock. VES was usefully supplemented by simultaneously measured induced polarization (IP) soundings which respond to the distribution of clay minerals. Transient electromagnetic sounding (TEM) proved to be the most rapid method of survey as no ground contact was required. Alluvial thickness was interpreted by resistivity-depth modelling of TEM data and was most reliable over low-resistivity argillaceous mudstone or shale bedrock.

Particle Size Effects on Stockpiling and Spreading Agricultural Limestone

AbstractStockpiling of agricultural limestone is a necessity in many agricultural regions due to transportation and production limitations. Particle size influence on stockpiling and spreading ground limestone must be quantified in order to produce a material that is effective in neutralizing soil acidity and can be uniformly spread after weather‐exposed storage. Effects of particle size on bulk density, percent moisture, and spread pattern uniformity by a commercial twin‐spinner bulk spreader were measured. Calcitic and dolomitic limestones with &gt;60% passing a 100‐mesh (150 µm) sieve bridged in the spreader body and resulted in uneven flow to the spreader spinners. Handling problems were not encountered with materials having &lt;55% passing a 100‐mesh sieve. Ground limestones with particle size distributions of 85 to 88, 48 to 61, and 39 to 56% passing 20‐ (850 µm), 60‐ (250 µm), and 100‐mesh sieves, respectively, were evenly spread after outdoor storage. Bulk densities ranged from 1.34 to 1.53 g/cm3 while moisture contents varied from 0.7 to 6.0%.

Automatic Rubber Diversion Dam in the Los Angeles River

The Los Angeles Department of Water and Power has for 45 years maintained a 30‐acre spreading ground located adjacent to the south side of the Los Angeles River between the Walt Disney Studios and Forest Lawn Cemetery. Over the years the department has been diverting water from the river by means of a 5‐ft wooden dam, which raised the water sufficiently high to take it through gates and carry it over the spreading grounds. Whenever there was more than 40‐50 ppm silt in the water, the spreading grounds would silt off and would require cleaning after 6‐7 weeks of operation. If there was 400‐500 ppm turbidity, the basins would choke off even sooner. The normal method of operation during such periods was to bypass the muddy waters, because maintenance costs averaged around $6,500 per cleaning of the 30‐acre basin. Also, because the Los Angeles River is a flood control channel, the wooden dam diversion structure was designed to wash out under any major runoff down the Los Angeles River. The net result was that the percentage of water reclaimed in the spreading basin was rather small as compared to what could be saved if the dam could be operated whenever there was water available in the river. One solution was to construct a diversion dam of some material which would withstand the abrasion of waterborne rocks and sand, would collapse so flat on the concrete channel floor that roots, floating trees, and general trash would not become entangled, and yet could be easily raised into a dam after the flood. Neoprene, a synthetic rubber which weathers well, was selected. The article discusses a prototype dam that was built first, and then the construction of a full‐size dam, operation of the dam, and other applications of the dam.

Discussion of “The application of the ring infiltrometer to diagnosis of irrigation problems in Southern California”

The paper is a valuable contribution to the study of infiltrometers and their uses. But some of the results presented are difficult for this writer to reconcile with the findings of a recent study, in which this writer had a pan made by the Los Angeles County Flood Control District. A brief summary of some of those finish and the methods used is presented below, in the hope that the author's closing discussion will explain some of,the apparent differences.The study by the Flood Control District [Brown and Sherman, 1954] included an attempt to evaluate individual basins of the City of Sierra Madre's spreading ground by the use of infiltrometer tests. Early tests used a single‐ring infiltrometer made from a steel barrel of 22‐inch diameter. Surface heads were varied, the maximum being approximately 33 inches. Later tests used an inner ring within the 22‐inch outer ring. Inner ring diameters of 6, 8.5, 10 and 12 inches were used.