Wick Drains Research Articles

Assessment of Soil Consolidation Techniques in Ecuador: Preloading and Wick Drains in the Exodo-Fertisa Project

Assessment of Soil Consolidation Techniques in Ecuador: Preloading and Wick Drains in the Exodo-Fertisa Project

Degradation of straw-based wick drain and its effect on consolidation

The recycling of straw, a type of agricultural waste in a large volume, has considerable attention, and attempts have been made to fabricate straw-based wick drains in soft clay ground improvement. Although it has low carbon emissions and is environmentally friendly, the biodegradation process of wick drains and its effect on consolidation need to be further investigated. In this study, the biodegradation process was examined by subjecting straw and plastic wick drains to degradation tests in soils from the prototypical project for comparison. The results show that the degradation of straw wick drains exhibits a decrease in the discharge capacity and tensile strength, and the degradation percentage of both exceeds by 30% after 240 days, whereas the mass loss is only 10%. After degradation, the abundance of cellulose-degrading bacteria increases by 3–10%, respectively. The biodegradable behavior of straw wick drains is achieved by the rapid community succession of multiple degrading bacteria and the population growth of cellulose-degrading bacteria. Afterwards, the theoretical calculation model considering the drain degradation was performed to understand the consolidation procedure, suggesting the effective substitution of straw wick drains.

Large-scale testing of electro-osmosis with enhanced wick-drain techniques for dewatering iron mine tailing

In geotechnical engineering, two conventional methods, electro-osmosis, and wick drains (also known as prefabricated vertical drains or PVD), are commonly employed to mechanically enhance fine-grained saturated soils. This research aims to combine these two methods to develop a novel approach. Various configurations were examined, and comparisons were made between the new product and each method individually to identify the optimal configuration, pattern, and degree of improvement. Samples were collected from the thickener at the Golgohar iron ore mine and arranged into seven large-scale testing pools. Square and triangular patterns, along with constant and alternating poles, were investigated in this study. The results demonstrated that the combination of these technologies improved the mechanical properties, with the most significant enhancement in undrained shear strength observed in pools employing an enhanced Wick drain featuring constant poles and a triangular pattern.

Analysis of Land Subsidence in Peatlands in the Awareness Area of Pekanbaru, Riau, Indonesia

This study area is administratively located in Parit Indah District, Bukit Raya District, Pekanbaru City, Riau Province. Geographically, the research area is located at coordinates 0° 28' 30.92" N 101° 28' 9.45" E N 0° 27' 25.63" - 101° 29' 47.30" E. The aim of this study was to find out the effect of peat soil types on subsidence. The data collection method in this study was carried out using sieve analysis, water content analysis, specific gravity, subsidence analysis, and soil testing in the laboratory. The effect of peat soil on subsidence has a significant effect between the type of peat and subsidence, the higher the maturity level of the peat, the lower the level of subsidence on peat soil. Based on the study's results, the soil consolidation test with a depth of 75cm-3m had a soil settlement value of 0.467. It is recommended to do this to reduce the impact of subsidence in the land area such as the research area so that it does not have too much impact on the construction which is carried out by hardening the location using the vertical wick drain method, as well as for building foundations it can be done using chicken claw foundation.

Analysis of Land Subsidence in Peatlands in the Awareness Area of Pekanbaru, Riau, Indonesia

This study area is administratively located in Parit Indah District, Bukit Raya District, Pekanbaru City, Riau Province. Geographically, the research area is located at coordinates 0° 28' 30.92" N 101° 28' 9.45" E N 0° 27' 25.63" - 101° 29' 47.30" E. The aim of this study was to find out the effect of peat soil types on subsidence. The data collection method in this study was carried out using sieve analysis, water content analysis, specific gravity, subsidence analysis, and soil testing in the laboratory. The effect of peat soil on subsidence has a significant effect between the type of peat and subsidence, the higher the maturity level of the peat, the lower the level of subsidence on peat soil. Based on the results of the study, the soil consolidation test with a depth of 75cm-3m had a soil settlement value of 0.467. It is recommended to do this to reduce the impact of subsidence in the land area such as the research area so that it does not have too much impact on the construction which is carried out by hardening the location using the vertical wick drain method, as well as for building foundations it can be done using chicken claw foundation.

Vertical Capillary Barriers and Wick Drains to Mitigate the Rain-induced Slope Failures: Numerical Analysis

Slope failures are catastrophic when they suddenly occur in human habitats. The stability of slopes gradually diminishes with heavy rainfall due to the increase in pore water pressure; subsequently, the shear strength of the slope soil decreases. The effect of rainwater on the instability of slopes was studied in this research with respect to factor of safety values. Accordingly, finite element analysis and limit equilibrium analysis were conducted using a 2D model of a soil slope in SEEP/W and SLOPE/W programs to observe the responses of the slope soil profile under heavy rainfall. Movement of the wetting front and the fluctuation of the groundwater table were studied to develop a drainage mechanism, thereby to control the effect of infiltrated rainwater on slope failure. A conceptual method was introduced in this study by developing a numerical model with an effective drainage system which consists of vertical capillary barriers with combination of horizontal wick drains in a cascade manner in the slope. This method exhibited high stability of the slopes even with continuous rainfall for number of days, therefore, applicable as a sustainable prevention method of slope failures.

Settlement Analysis of Pipe Culvert Situated in Soft Clay Treated with Prefabricated Vertical Drains

Engineering structures built on soft and compressible soils are often subjected to a long‐lasting consolidation settlement. It is difficult to achieve an acceptable level of consolidation during the first few years/days of operation. Similarly, the culvert structure provided at station km 159 + 112 of the Awash‐Kombolcha‐Hara Gebeya Railway Project, Ethiopia, was situated along the route traversing soft clay ground of significant thickness. For the intention of reducing consolidation time and lessening the precarious impact of the postconstruction settlement, the soft clay ground was treated with preloading and prefabricated vertical drains. However, the culvert structure is currently undergoing consolidation settlement with varying magnitudes. The vertical deformation of the culvert site is monitored using settlement gauges installed at the site. Monitoring of the site continued for 120 days to track the extent of ground deformation at the culvert site. However, because of environmental and technical factors like calibration and alignment errors, the settlement instrument readings may be exposed to uncertainties, which may probably affect the safety of the culvert structure. Hence, the study is primarily aimed at evaluating the field deformation performance of the culvert structure for 120 days of the consolidation period through numerical analysis and comparing the result with the site settlement monitoring data. The critical effect of wick drain and some key parameters (fill thickness and wick drain spacing) were also scrutinized. Finite element‐based numerical modeling was conducted by using the 2D GeoStudio/SigmaW package, and the Modified Cam Clay Constitutive model was adopted. The conducted numerical analysis revealed that the finite element result has good agreement with the field settlement monitoring data with only 0.0305 m maximum deviation in which the numerical analysis result remained greater for majority of the consolidation time. It can also be inferred that granular fill thickness and wick drain spacing were the key parameters impacting the settlement of the culvert structure.

Application of different techniques to enhance sludge drying paved bed drying process

Massive quantities of sludge are being generated with the rise in populace and increase of wastewater produced. Ordinary sand and paved drying beds are still designed within the conventional way. This research focused on creating modern procedures to reduce the drying up duration for the combined sludge produced. This included the use of direct thermal solar heated water pipes, wick vertical drain, and horizontal filtration combined with bottom drainage for three built tanks utilizing freshly combined primary and secondary sludge with initial concentrations ranging from 0.42%−3% for the different filling cycles performed over two stages under changing climatic conditions. In-situ measurements of solid content, temperature and sludge height were taken. For stage one, the solids content reached 8.53% for solar tank, 7.42% for wick vertical drain tank and 17.4% for the conventional paved dry tank after 105 days of operation. For stage two, solids content reached 6.9% and 6.6% for solar and wick vertical drain tanks respectively and 7.93% in the conventional PDB combined with horizontal flow after 35 days of operation. Results are promising and could lead to better operational performance of PDB while decreasing the required time required; hence maximizing and upgrading the existing facilities.

Improvement of Soft Organic Clay Soil Using Vertical Drains

The design of foundations based on soft clay is still a very challenging problem. Three experimental cases were performed to examine the action of soft clay: the first case without drains, the second case with sand drains and the third case with prefabricated vertical drains (PVDs). Two-dimensional finite element analysis was carried out using PLAXIS 2D and its findings were compared to previous experimental results where good consistency was found. Parametric study was conducted with a variation in the size, length and diameter of sand drains. The length and spacing of the PVD, the diameter of the smear zone and the permeability of the smear zone were also studied. Results have shown that PVD is preferable to the improvement of soft clay rather than sand drainage systems. The sand drains decreased the time of 90% consolidation by (90.8%) using 50 cm diameter, 2 m spacing and 25 m length, and the PVDs decreased the time of 90% consolidation by (94.4%) using 4 mm × 10 cm dimensions, 2 m spacing and 25 m length. Both sand drains and PVD are effective in decreasing the consolidation time. The results of this paper concluded analytical formula that indicate the percentage of wick drain consolidation.

Study on the Behavior of Geosynthetic-Reinforced Pile-Supported Embankments in Soft Ground Improvement Solutions

Embankments on soft ground often encounter many problems such as settlement, slip, and deformation that exceed the permitted limit. In recent years, a new type of foundation called "geosynthetic-reinforced pile-supported embankments" has been used. Until now, although the behavior of this foundation type has been analyzed and certain results have been presented in literature, calculation methods do not allow geotechnical engineers to calculate the results accurately. This study builds up a field experiment model to investigate the impacts of arching effects in the sand buffer layer on pile heads to increase the load transfer on the pile caps. The results indicate that the stress distribution on the pile cap is 10.48 times higher than the stress on the surrounding soft soil. Hence, the ground improvement method using piles and geosynthetic reinforcement can be applied to roadbeds and industrial warehouses on soft soil conditions, which helps to shorten the construction time compared to other ground treatment methods such as preloading, vacuum pumps, wick drains, etc.

Effect of Improvement and Application of Composite Prefabricated Vertical Drain Method in Marine Soft Ground: A Case Study

One of the commonly used techniques to improve marine soft ground is the drainage consolidation method by plastic board drains (PBDs). But some complex marine soft ground will cause construction inconvenience of PBDs in certain areas of these sites, thus affecting the improvement effect. An alternative possible approach to overcoming these deficiencies may be the combination of PBDs and sand wick drains (SWDs) (i.e., composite prefabricated vertical drains (CPVDs)) as vertical drainage channels in the same site. In order to verify the suitability and performance of this method in marine soft ground improvement, a case study was performed based on the field monitoring and construction of the marine soft ground of an intercity express railway project in China. The construction procedure using the CPVD system, the field monitoring instrumentation scheme, and the design of fill surcharge level were described, and the field monitoring data were presented. The settlement characteristics, dissipation features of pore water pressure, and the horizontal movement pattern were assessed. In addition, predictions of ultimate settlement, postconstruction settlement, and consolidation degree were discussed by applying a modified hyperbolic model. The results show that the marine ground improved by the CPVD system is suitable for the construction of intercity express railway and high‐speed railway. The improvement construction period of complex marine soft ground will be greatly shortened by the proposed parallel construction programme. This work will provide technical supports and application reference for the improvement of the similar marine soft ground.

Effects of frequency and confining pressure on consolidation drainage behavior of soft marine clays

This article presents an experimental investigation on the dynamic consolidation (DC) drainage behavior of soft marine clays. A sinusoidal harmonic load with different frequencies was applied to simulate the DC method in which the conventional impact load was replaced by the cyclic load. Four geotextile-filter strips were used to form the side drainage channels simulating the wick drain method. A series of loading tests were conducted on soft soil specimens at different confining pressures (i.e., 20, 40, 70, and 100 kPa) and different vibration frequencies (i.e., 0, 0.5, 1, 1.5, 2, and 5 Hz). Test results showed that both confining pressure and frequency have significant influences on the drainage behavior of soft marine clay specimens. The magnitude of drainage volume consistently decreases linearly with increasing confining pressure. Compared to static loading condition, specimens under cyclic loading condition at different frequencies show a better drainage performance. Specimen at applied frequency of 1 Hz exhibits the maximum cumulative drainage volume due to the resonant effect.

Modelling the behaviour of the Ballina test embankment

As part of the Australian Research Council Centre of Excellence for Geotechnical Science and Engineering (CGSE) research program, an instrumented embankment was constructed on soft ground with and without the use of prefabricated vertical drains at Ballina in northern New South Wales (NSW, Australia). To better understand the behaviour and to help build a more robust geotechnical model for the Ballina site, a comprehensive characterisation study was carried out on the subsurface soil. This paper presents the results of a back analysis on the test embankment with wick drains at Ballina, in which the soft clay layers have been modelled using Modified Cam Clay. A 2D plane strain finite element model in ABAQUS was used to predict instrumentation recordings for a 3year period. The results of the back analysis suggest that the Modified Cam Clay model is able to predict the behaviour of the embankment but care is needed in parameter selection to account for anisotropy, destructuration and most significantly, time dependent behaviour. The complex evolution of soil properties during wick drain installation and consolidation also created difficulties in confidently describing individual soil parameters.

Electro-osmotic consolidation of marine hydraulically filled sludge ground using electrically conductive wick drain combined with automated power supply

ABSTRACTElectro-osmosis (EO) methods have not been widely used for the drainage consolidation of soft clay soils in practice because of two key problems; (i) metallic electrode corrosion, and (ii) high electric energy consumption. With recent advancements of conductive plastics, there has been interest in using conductive plastic electrodes instead of metallic electrodes to accelerate drainage of soft clay soils. This paper presents the details of a field EO test using a type of new patented electrically conductive wick drain (ECWD) and a specially designed automated power supply (APS) on a hydraulically filled sludge ground in Jiangsu Province, China. The in-situ investigations and laboratory tests were conducted to evaluate the improvement effectiveness after performing EO treatment for a period of 36 days (including a continuing intermittence of 16 days). The results suggest that the EO technique using the ECWD combined with the APS (i) decreased the average moisture content of the sludge from 62 to 39%; (ii) increased the vane shear strength from ∼0 to 25.5 kPa. In addition, the ground bearing capacity also increased from ∼0 to 74 kPa. The electric energy consumption for this EO treatment is 5.6 kWh/m3. Moreover, the prediction models for electric current I and cumulative drainage Q during EO are validated using data from the present field and laboratory tests. Investigations to date suggest that the new ECWD combined with APS presented in this paper is encouraging for consolidating the large area of soft clay soil with high water content to achieve favourable conditions with respect to increase in shear strength at an acceptable cost.

A numerical evaluation of continuous backfilling in cemented paste backfilled stope through an application of wick drains

Cemented paste backfill (CPB) is gaining popularity in many underground mines worldwide. Sufficient water is added into CPB to make a flowable material for pipe transportation. Barricades are built near the drawpoints to prevent in-rush of the fill slurry. To avoid barricade failures resulting from excessive backfill pressures, backfilling is typically performed with a plug pour followed by a final pour. The interval between the two pours should be shortened or removed to increase mining productivity and avoid pipe clogging. Recently, Li proposed to apply wick drains in backfilled stopes to promote drainage and consolidation. The preliminary simulations by considering an instantaneous filling indicated that the drainage of CPB can be significantly accelerated by using wick drains. Barricade was not considered. Here, some new numerical modellings are presented with more representative filling sequences, stope geometry, and different draining configurations. The results illustrate that the stope can be backfilled continuously by using wick drains.

Assessment of smear parameters for use in wick drain design

Soft clay becomes remoulded around wick drains during their installation. The effects of remoulding can be taken into account in design by adopting an analytical method incorporating the radius of smear and the permeability of the remoulded soil in the smear zone. However, these parameters are usually not known and are estimated largely based on experience and guidance provided in the technical literature. Back analysis of settlement data from an embankment constructed on soft Pimlico Clay in Australia with a wick drain spacing of 1·5 m in an equilateral triangular configuration is performed to assess the potential smear parameters. A chart showing variations of permeability with smear radius is presented to assist with selection of design parameters for wick drains installed in soft Pimlico Clay. Effects of wick drain spacing on the permeability of the remoulded soil are investigated through back analysis of embankments constructed on wick drains spaced at 1·0 m and 1·35 m in an equilateral triangular configuration. Although the embankments are not constructed in identical ground conditions, there is no evidence that reducing the spacing between the wick drains causes the average permeability ratio to increase.

In Situ Tests—Predicted vs. Observed Settlements: A Comparative Case Study

This paper aims to deal with the comparison of the estimated settlements derived by in situ tests with the observed settlements in site, in order to evaluate the accuracy of settlement prediction by in situ tests, in comparison not only with site observation by topographic means, but also with the values of settlements derived by numerical analysis by means of PLAXIS 2D and 3D. The site where are carried out the tests and periodically are observed the settlements since the beginning of construction process, is located in the Oil Product Terminal, at the industrial park of Porto Romano, Durres, Albania. The main purpose of this project was the ground improvement by using preloading method in order to prevent liquefaction process and settlements. The data used to conduct this study are taken by the site investigation done after inserting into the soil vertical drains made of columns of free—draining gravel (gravel pile drains) until 14 m depth and center-to-center spacing of 2 m, and wick drains (premanufactured) until 25 m depth and center-to-center spacing of 1.8 m. The observed settlements are periodically measured by topographic equipments. This paper will present the conclusions derived by settlement analyzes from in situ tests and site observations. constructions in soft and sensitive soils. One of these case studies is presented in this paper. The aim of this study is to evaluate the settlement by using the data obtained by a series of piezocone tests and seismic dilatometer tests (hereafter mentioned as CPT and DMT), including also the comparison of CPT and DMT—calculated vs. observed settlements, in order to evaluate the accuracy of settlement predictions based on these tests.

A new concept of backfill design—Application of wick drains in backfilled stopes

Backfilling represents an environmentally friendly mining waste disposal technique. It is increasingly used in underground mines all over the world. However, its primary purpose remains to improve ground stability and to reduce ore dilution. Previous investigations have shown that fill drainage plays a key role in backfill and barricade design. With a poor drainage system in the backfilled stope, the required dimension of barricade, which is constructed at the base of the stope near the drift entrance, has to be increased. A poor backfill drainage system can also lead to a significant increase in drainage waiting time and further reduction in mining productivity. In this paper, the drainage of conventional backfill design in backfilled stopes is briefly reviewed. For the first time, the application of the wick drain is introduced in the backfill within mine stopes. The drainage improvement from the introduction of the wick drain is illustrated using numerical modeling.

Ground improvement efficiency and back-analysis of settlements

The ground improvement works carried out for the construction of five oil tanks at the Chiriqui Grande Phase II Oil Terminal, Chiriqui Grande, Panama, and their results are presented herein. The site is underlain by some 28 m of loose/soft, poorly graded, silty sands to clayey sands and silts. Ground improvement was used to provide the required bearing capacity and reduce the expected total and differential settlements. To fulfil the technical specifications, two ground improvement techniques were used in association with preloading: wick drains to full depth of the soft layers and stone columns in the upper 18 m. Stone columns are commonly installed as partial replacement to improve a soft ground, increasing its bearing capacity and accelerating its primary consolidation. Wick drains are used to accelerate the consolidation of soft clayey soils. Particular emphasis was given to the behaviour of the treated ground under the preloading fill: a back-analysis was carried out on measured settlements and pore pressures; the improvement of the ground and the degrees of consolidation achieved at the end of the preloading are highlighted; some correlations were derived and they provide an interpretation of the overall behaviour of the improved ground; estimates of the settlements for the short and long term are presented, the short term being that of the hydrotest and the long term being the design life of the oil terminal. They are based on results of preloading for their primary consolidation part, and on reasonable assumptions for their long-term creep (secondary consolidation) part. The estimates are compared to the actual hydrotest survey results.

Characterization of thick varved-clayey-silt deposits along the Delaware River by field and laboratory tests

The existence of thick compressible varved clayey silt deposits along the Delaware River presents one major obstacle for design and construction of structures or industrial facilities in this region. To understand the characteristics of this thick weak soil layer and then develop reliable soil parameters for future earthwork design and construction, a comprehensive soil testing program was carried out. The program consisted of both in situ tests [e.g., standard penetration test borings, piezocone penetration test (CPT) soundings, Marchetti flat dilatometer test soundings, seismic shear wave test soundings, CPT pore pressure dissipation tests, and field vane shear tests] and laboratory tests (e.g., soil index tests, consolidation tests, triaxial tests, and chemical tests). Additionally, a field surcharge test program with and without installation of wick drains was carried out to investigate the compressibility of the thick clayey silt deposit and the efficiency of wick drains to help accelerate consolidation. The field and laboratory test results showed that the varved clayey silt deposit was normally consolidated to slightly overconsolidated and moderately to highly compressible. Its physical properties were intermediate between those of Savannah muddy clay and Shanghai soft clay, while much closer to that of Shanghai soft clay. Due to its lamination structure in the horizontal direction, the horizontal consolidation coefficient of the varved clayey silts was significantly greater than that in the vertical direction. The measured undrained shear strength of the varved clay silt almost increased linearly with depth. The installation of wick drains in the thick clayey silt deposits accelerated primary consolidation, but showed no effect on the secondary consolidation under constant loading. The findings obtained from this study will be beneficial for future design and construction of earthworks along the Delaware River.