Effectiveness Of Geotextiles Research Articles

Consolidation behaviour of marine clay improvement by combined vacuum preloading with geotextile

ABSTRACT The traditional vacuum preloading method of prefabricated vertical drain (PVDs) has been widely used in practical engineering. However, the serious clogging effect around PVDs in the process of vacuum-preloading reinforcement can easily lead to a series of problems such as uneven settlement and large lateral displacement of soil after reinforcement, which seriously affects the application of PVDs in marine clay foundation treatment. In this paper, the effect of combined treatment of marine clay by geotextiles and PVDs on reducing the clogging effect around PVDs was studied by laboratory model experiment. The effects of geotextiles with different diameters and spacings on the surface settlement, excess pore water pressure and lateral displacement of the reinforced soil were analysed. The experimental results show that this method has obvious help on alleviating the above problems, thus providing a reference for the application of geotextile combined with vacuum preloading method to treat marine clay foundation in engineering practice.

Influence of collapse width on the effect of geotextile in controlling subgrade collapse based on symmetrical semisection model tests

Subgrade collapse is a frequent geological hazard all over the world, which seriously threatens safety of human life and economic development. Compared with conventional methods of collapse, employing geotextile basal reinforcement with the features of reinforcement and filtration can achieve better treatment. In this paper, four symmetrical semi-section model tests with different width of collapse treated by geotextile and one full-section model test were carried out. Data acquisition instruments and particle image velocimetry (PIV) equipment were applied to research soil pressure, vertical displacement of filling and tensile force of geotextile. The following results were achieved: the results obtained from symmetric semi-section and full-section model test was proximal so that the symmetrical semi-section model test had certain feasibility; the laying of geotextile basal reinforcement had good effect on collapse treatment; the width of collapse area was an crucial factor affecting the collapse treatment using geotextile and the geotextile with high tensile strength and enough buried depth should be employed when dealing with large scale collapse problems.

X-ray CT based clogging analyses of pervious concrete pile by vibrating-sinking tube method

Pervious concrete piles (PCP) have high permeability and strength. During installation by vibrating-sinking tube construction, liquified soil migrates into PCP, leading to clogging. To study PCP clogging, model tests and X-ray computed tomography analyses were carried out. The clogging depth, porosity, and excess pore water pressure dissipation were characterized. The effect of geotextile on PCP anti-clogging was evaluated. The results show an increase in target porosity and sampling depth significantly increased the PCP clogging depth. A preliminary model was proposed to evaluate the clogging of PCP. The results show that clogging can be solved by surrounding PCP with geotextile.

Effect of geotextile on reduction of reflective cracking induced by traffic load in asphalt concrete

Cracks appear in the early cement stabilisation base due to shrinkage. Pavement service life is reduced by the reflecting cracks under load coupled with environment. Geosynthetics can be used as an effective anti-reflective crack material to improve the asphalt concrete performance. Related studies mainly focus on the optimal material type and placement location of geosynthetics. However, the mechanism research of anti-crack propagation is limited and needs further investigation. The methods used to date are hard to reveal the anti-reflective crack mechanism of geosythetics. Therefore, geosynthetic materials cannot be used appropriately. Propagation and resistance characteristics of traffic induced reflective cracks with geotextile placed in the asphalt layer was investigated using extended finite element model. The effects of geotextile placement and tensile modulus were also investigated. Compared with other zones, the geotextile stress over the crack was significantly larger. The geotextile absorbed 15% of the total stress in the asphalt surface layer. The crack propagation stages and final crack length was separate when tensile modulus of geotextile reached 50 MPa. The geotextile with 100 MPa tensile modulus was found to produce the optimal effect on preventing crack. Geotextile placed at a quarter depth of the asphalt layer from the bottom had the best crack resistance.

Effect of geotextile and agrotextile covering on productivity and nutritional values in lettuce

Effect of geotextile and agrotextile covering on productivity and nutritional values in lettuce

Stability Analysis of Colombo–Katunayake Expressway (CKE) Using Finite Element and Limit Equilibrium Methods

Colombo–Katunayake Expressway (CKE) is the second major highway in Sri Lanka connecting the International Airport at Katunayake to Colombo, and this expressway is constructed over soft soils, predominantly peat. A research study was conducted to analyse the stability of two critical sections of the CKE project using finite element method (FEM), limit equilibrium method (LEM) and Matsuo chart. In the FEM, PLAXIS 2D package was used to simulate the behaviour by using four different types of analyses: (1) Mohr–Coulomb (MC) analysis: MC model for all soil layers; (2) MC-SS 1 analysis: soft soil (SS) model for peat and MC model for remaining soil layers; (3) MC-SS 2 analysis: SS model for peat and soft clay layers and MC model for remaining soil layers; and (4) MC-SS-SSC analysis: soft soil creep (SSC) model for peat, SS model for soft clay and MC model for remaining soil layers. Further, LEM analysis was carried out using SLOPE/W and obtained factor of safety (FOS) values were compared with the FEM analysis. In addition, effect of geotextile on the long-term stability was analysed in FEM. Based on the outcome of the FEM analysis, it was noticed that MC-SS 2 model is the best model to predict the actual field condition for soft soil with high overconsolidation ratio values. In addition, FOS values obtained from PLAXIS were in very good agreement with those obtained from SLOPE/W. Incorporation of geotextile improves the stability of the embankment, and the optimum stiffness of the geotextile should be selected for practical applications.

Effectiveness of geotextiles for road slope protection under simulated rainfall

Geotextiles are used to control soil losses in civil engineering. The effects of geotextiles on runoff and soil erosion have been documented; however, the conditions studied to date have been limited and are insufficient for the optimization of the selection and application of geotextiles for other sites. As a result, systematic studies of various rainfall intensities are still required. In this study, four geotextiles (coir blanket—CB, mixed coir and straw blanket—MCSB, straw blanket—SB and nonwoven fabric—NB) and a bare control group were examined under simulated rainfall events. Four rainfall intensities (24, 47, 71 and 93 mm h−1) were simulated for 60 min. The plots used in this experiment were 200 cm long by 100 cm wide by 40 cm deep at a slope gradient of 70 %. The tested soil was sandy loam, which is a primary soil type in northern China. The results show that geotextiles are more effective for soil loss control than for runoff control, especially in the case of stronger rainfall events. The effectivenesses of the geotextiles at reducing runoff and soil erosion decrease with increasing rainfall intensity; the geotextiles are most effective under moderate rainfall intensity levels. NB is the most effective geotextile for reducing runoff, while it reduces soil loss only below a rainfall intensity level of 47 mm h−1. The natural geotextiles can reduce both runoff and soil erosion. For runoff control, SBs are more effective than MCSB, followed by CBs. For soil erosion control, CBs are the most effective, followed by MCSBs and then SBs.

Liquefaction potential of reinforced silty sands

In this study a series of cyclic triaxial tests were performed to examine the undrained dynamic resistance of silty sand reinforced with various arrangements of geotextile layers. The silt content of samples varies in percentage from 0, 10, 20, 30, 40 and 50%. A total of 32 laboratory cyclic triaxial tests have been performed on silty sand samples reinforced with geotextile layers in different depths. All tests were performed with 100 kPa confining pressure, subjected to an isotropic consolidated undrained (CIU) condition. The tests were conducted at a frequency of 2 Hz. Results indicate that both the geotextile arrangement and the silt content were most essential in the liquefaction potential of reinforced sands. An increase in the number of geotextile layers enhanced the cyclic resistance of reinforced samples against the liquefaction potential. It was also found that when the geotextile layer was posited near the top of the specimen (load application part) the liquefaction resistance would increase (e.g. for clean sands, the improvement of liquefaction resistance caused by the geotextile layer had a 0.2 depth, and the sample height was 5.5 times greater than the geotextile layer inserted in mid height of sample H). Based on the obtained results, effects of geotextile on liquefaction resistance decreased as fines content increased to about 33%. Further increase in the fines content however, would lead to higher in reinforcement advantages. The liquefaction improvement is more effective with a higher number of geotextile layers. The results also revealed that the reinforcement effect in FC≈33 % is at its lowest amount.

APPLICATIONS OF INNOVATIVE MATERIALS FOR PERFORMANCE IMPROVEMENT OF FLEXIBLE PAVEMENT OVER EXPANSIVE SUBGRADE

Expansive soils are one of the most problematic materials that are widely encountered in significant land areas in several parts of the world; like Africa, Australia, India, United States and Canada. The South Gujarat region in India have majority of top soil as black cotton soil. The black cotton soil has characteristics of shrinking on drying and heaving on wetting. This soil being expansive creates several types of damages to pavement structures, and in some cases the pavement may even become unserviceable. The normal climate condition of study area shows short wet and long dry period which aggravate the problem of swelling and shrinkage. The IRC: 37 - 2001, Annexure - 4 suggest 0.6 to 1.0 m thick non-cohesive soil cushion on the expansive soil for road construction which led to higher cost for road construction. Also for new urban areas it is difficult to raise the embankment or to excavate the subgrade upto such a depth due to existing structures and under laying service lines. To provide economical solution along with feasible application two innovative materials were used namely, CONSOLID and Geotextile for flexible pavement. The CONSOLID application shows the great improvement of CBR values helping the overall stability of the pavement. The Geotextile provided below the pavement components to act against the heaving of the swelling soil at the same time it helps as drainage layer also. Field study is undertaken to observe the effect of Geotextile in flexible pavement performance and 2 specific boundary conditions are created for observations. The Observations shows about 50 % reduction in shrinkage effect for paved road reinforced with Geotextile subjected to drying and wetting cycles. Both the materials are having its unique advantage in the performance improvement of flexible pavement over expansive subgrade.

Evaluation of erosion control geotextiles on steep slopes. Part 1: Effects on runoff and soil loss

Geotextiles have been demonstrated to be effective in reducing erosion and subsequent slope degradation processes. However, most studies devoted to assessing the effectiveness of those elements have considered small or intermediate slope gradients (normally ≤30°), whereas real engineering works often lead to steeper slopes needing protection. In addition, although a large amount of laboratory studies exist on this topic, there are few articles reporting field experiments which consider large plots, real precipitation and prolonged study periods. This paper is the first of two in which the performance of erosion control geotextiles on steep slopes (45° and 60°) has been assessed. In this paper, the influence of geotextiles on runoff and soil loss reduction was evaluated. The second paper focuses on the effects of geotextiles on the establishment and growth of vegetation on the slope. The research was carried out on an experimental embankment built in Pamplona (Spain) following standard construction procedures in order to resemble real engineering slopes. Two biological geotextiles (jute net and coir blanket) and a synthetic polyester geogrid, installed in two positions (surface-laid and buried), were evaluated and compared with a vegetated hydroseeded control plot. After each significant rain event, runoff and soil loss amounts produced on each plot were recorded. The results showed that coir and jute geotextiles produced 2–3 times larger runoff volumes than the control plots on both the 45° and 60° slopes, whereas the synthetic geogrid did not give significantly different runoff rates from the control (at p<0.05). Geotextiles were more effective in reducing soil loss at 45° than at 60°. The most effective treatment was the surface-laid geogrid, with a median Soil Loss Reduction Effectiveness (SLRE) of 76% and 53% for the 45° and the 60° slopes, respectively. At 45° the coir blanket showed lower soil losses than the control (median SLRE of 61%), but at 60° its protection action was more irregular (median SLRE of only 8%). The jute net and the buried geogrid produced lower erosion rates (median soil loss of 3.2gm−2 and 2.1gm−2, respectively) than the control (median soil loss of 3.6gm−2) at 45°, but at 60° the erosion rates observed were similar to those of the control. In short, the surface-laid geogrid produced the lowest soil loss rates. However, when buried, the geogrid did not effectively control erosion, at least not that of the upper soil layer. Thus, its surface installation seems to be a better option. In cases where burial is preferred for aesthetic reasons (i.e. hiding the geogrid), a higher soil loss must be assumed.

Effect of Geotextile and Prefabricated Vertical Drains Used in Soft Soil Foundation

Based on the generalized formulation of two dimensional Biot′s theory of consolidation, the effect of geotextile and prefabricated vertical drains (PVDs) using in soft soil foundation was studied with nonlinear finite element method. The dissipation of excess pore pressure, vertical settlement and lateral displacement of foundation were contrasted between foundations with and without PVDs. It is found that the vertical settlements become lager, the lateral displacements become less and the bulges at the toe of embankment become less at the same time of consolidation when PVDs are used. And the stability of embankment improved for the bearing capacity of soil enhanced with excess pore pressure dissipated fast. Meanwhile, the axial force of geotextile become less when PVDs are used. Those changes showed that the design of foundation can be optimized by shortening the time of consolidation when PVDs are used.

Use of palm-mat geotextiles for soil conservation: I. Effects on soil properties

Abstract Despite geotextile-mats having the potential for soil conservation, field studies on the effects of geotextiles on soil properties are limited. Hence, the utilization of palm-mat geotextiles as a potential soil conservation technique was investigated at Hilton, east Shropshire, U.K. (52°33′5.7″ N, 2°19′18.3″ W). Geotextile-mats constructed from Borassus aethiopum (Borassus palm of West Africa) and Mauritia flexuosa (Buriti palm of South America) leaves are termed Borassus mats and Buriti mats, respectively. Field experiments were conducted at Hilton during 2007–2009, to study the impacts of Borassus and Buriti mats on selected properties of the topsoil (0–5 cm). Ten fixed plots (10 × 1 m on a 15° slope) were established, with duplicate treatments. The treatments were: (i) bare soil; (ii) permanent grassed; (iii) bare soil with 1 m Borassus-mat buffer strips (area coverage ~ 10%) at the lower end of the plots; (iv) bare soil with 1 m Buriti mat buffer strips (area coverage ~ 10%) at the lower end of the plots; and (v) completely-covered with Borassus mats. Initial and final soil samples of the topsoil were collected and analysed for bulk density, aggregate stability, soil organic matter (SOM), total soil C (TSC), total soil N (TSN) and pH. Results indicate that, apart from Borassus completely-covered plots, soil bulk density increased and aggregate stability decreased in all plots after two years. Despite decreases in SOM contents in bare plots, SOM content did not change after two years in the grassed and geotextile treated plots. Treatments had no effects on changes in pH, TSC or TSN. Both Borassus and Buriti mat-covers within the buffer strip plots had little impact on SOM, TSC and TSN changes compared with bare soils within the same plots. Thus, Borassus buffer strip plots were very effective in maintaining some soil properties (i.e. SOM, TSC, and TSN) after two years of erosion by water. In summary, utilization of Borassus mats as buffer strips was very successful in conserving soil properties on a loamy sand soil.

Effectiveness of geotextiles in reducing runoff and soil loss: A synthesis

Abstract Despite geotextiles having potential for soil conservation, limited scientific data are available to assess the effects of geotextiles in reducing runoff and water erosion. Hence, the objective of this review is to analyse the effects of plot length (L) and other possible affecting factors [cover percentage (C, %), slope gradient (S), rainfall duration (D), rainfall intensity (I), sand, silt and clay contents, soil organic matter (SOM) content and geotextile type (natural or synthetic)] on the effectiveness of geotextiles in reducing soil and water loss, based on reported experimental data. From linear regressions, C (%) and soil sand, silt and clay contents are found to be the most important variables in reducing SLR (ratio of soil loss in bare plots to that in geotextile treated plots) for splash, C (%) for interrill and D (min) for rill and interrill erosion processes, respectively. Soil clay and silt contents and D are key variables in decreasing RR (ratio of runoff from bare plots to that from geotextile treated plots) for interrill, and clay content for rill and interrill erosion processes, respectively. The linear relationship between mean b-value (geotextile effectiveness factor in reducing soil loss) and L of all studies was not significant (P > 0.05). The same is true for the relationship between L and SLR, and L and RR. However, when L is added to an equation as an interaction term with C (%), geotextile cover is significantly (P

Effects of geotextiles on lateral pressure and deformation in highway embankments : Edgar, T V; Puckett, J A; D'Spain, R B Geotext GeomemV8, N4, 1989, P275–292

Effects of geotextiles on lateral pressure and deformation in highway embankments : Edgar, T V; Puckett, J A; D'Spain, R B Geotext GeomemV8, N4, 1989, P275–292

Effects of geotextiles on lateral pressure and deformation in highway embankments

A procedure to lower the lateral loading acting on the back of a highway abutment wall utilizing geotextiles is described. A gap is formed between the wall and the geotextile reinforced backfill using either corrugated cardboard (which is wetted after construction) or removable plywood forms. This allows the backfill to deform and go into the active state. The fabric sustains the resulting tensile forces, essentially forming a free-standing fabric wall behind the abutment. Laboratory testing indicates that less than 25 mm lateral movement is required to reduce lateral loads by 90 percent. Four reinforcement schemes were compared on two Interstate bridges. The fills were instrumented with inclinometers, Sondex tubing and pressure cells. The results indicate that an initial gap reduces the lateral load to essentially zero and settlements were no greater with the voided system than that experienced by a nonvoided fill