Manoj Chopra

Effect of Rejuvenation Methods on the Infiltration Rates of Pervious Concrete Pavements

Pervious concrete pavements in low-traffic urban areas such as parking lots reduce storm water runoff and also minimize water pollution. However, there are concerns about their expected clogging and consequential reduction of hydraulic performance in the long run. The pervious concrete pavements can be declogged using rejuvenation methods such as vacuum sweeping, or pressure washing, or a combination of both. This paper presents the results of our study that focused on the hydraulic performance of pervious concrete pavements. The study included field and laboratory investigations to evaluate the infiltration capacities of the pervious concrete cores and the underlying soils and the usefulness of rejuvenation methods in restoring their hydraulic performance. As a result of this research program, a new field test device, called the embedded ring infiltrometer, was developed for evaluating the infiltration rates of newly installed pervious concrete pavements. The results of this study indicate that the rejuvenation methods can substantially restore the performance of pervious concrete pavements for better management of storm water.

Development of BEM for thermoplasticity

Abstract A boundary element method (BEM) for general thermoplastic analysis is presented. A thermally-sensitive two surface material model is used to simulate constitutive behavior. The nonlinear system of equations, arising from an initial stress approach, is solved using a new Newton-Raphson solution algorithm. The stress tensors are collapsed into a scalar variable using certain characteristic tensors arising out of the constitutive equations. This leads to a simpler system requiring much less computation. The solution algorithm is iterative in nature and checks for convergence at the end of each increment. The resulting robust analysis tool is then utilized in solving several practical applications to illustrate the growing importance of BEM as an alternative to the finite element method.

Generalized boundary element method for solids exhibiting nonhomogeneities

The current paper presents a generalized boundary element method to solve the material nonhomogeneous isotropic problems. A boundary integral equation is derived in which the traction kernel includes the full nonhomogeneous elasticity tensor and the domain integral involves the first order derivatives of the displacement kernel and the displacement itself as arguments of its integrand. By using a radial basis function to approximate the domain integrand and assuming the radial basis function is the divergence of a vector function, an anti-divergence scheme is developed to convert the domain integral into a boundary integral. Thus, the numerical implementation is performed with only a boundary mesh and internal collocation points for calculation. The numerical results validate the feasibility of the present approach.

Pervious Pavement Systems in Florida—Research Results

Pervious pavement systems are being studied for stormwater quality and quantity control and as a major component of low impact development (LID). To assess the potential of several types of pervious pavement systems, the Stormwater Management Academy at the University of Central Florida is studying the behavior of these systems at its field laboratory. These pervious pavements are also considered as part of the new Stormwater Rule in the state of Florida. Research is being conducted on five types of pervious pavements, namely pervious concrete, Flexipave, porous asphalt, and two types of brick pavers. One more pavement system called Filterpave has recently been installed and is currently undergoing testing. This paper will present the results of the infiltration testing on these systems. Keeping in mind the long-term performance and maintenance requirements, these pavements are intentionally being loaded with sediment (sand and fine grained crushed limerock) to simulate clogging as indicated by significant reduction in their infiltration capacity. The pavements are then subjected to a rejuvenation technique using a vacuum sweeper truck. This paper will also present the results of these rejuvenation techniques on the performance of the pavements. This paper aims to update the water resources community on the new developments with these types of pavements.

Evaluation of the Use of Recycled Concrete Aggregate in French Drain Systems

Recycled concrete aggregate (RCA) is often used as a replacement for virgin aggregate in road foundations (base course), embankments, hot-mix asphalt, and Portland cement concrete. However, the use of RCA in exfiltration drainage systems, such as French drains, is still uncommon. The primary concerns with using RCA as drainage media are excessive fines and calcite precipitation that can cause a reduction in permeability performance. This study investigates the potential benefits of RCA as drainage material. This paper presents and discusses: (1) the results of a nationwide survey on current practices and policies, (2) physical and chemical properties, (3) effective fine-removing methods, (4) re-cementation potential, (4) permeability (under varied fine content), and (5) long-term drainage performance of RCA as drainage material. Test results indicate that RCA No. 4 gradation does not restrict the flow of water, but the RCA fines being generated during aggregate handling process (e.g., stockpiling, placing and transporting) may cause clogging buildup over time.

Investigation on Clogging Potential of Recycled Concrete Aggregate in French Drain Systems

Recycled concrete aggregate (RCA) has been used as replacement for virgin aggregates in road foundation, embankment, portland cement concrete, and hot-mix asphalt. The use of RCAs in drainage systems (i.e., base/subbase layer and French drain) has not received much attention because of the poor drainage performance of RCAs. Two major causes are (1) the accumulation of excess fines precipitated on geotextile and (2) deposition of calcite precipitation over time. To date, not many studies have been conducted on the drainage performance of RCAs. This limited and unavailable information hinders the use of RCA as drainage materials although there are many benefits to these in promoting sustainability in geotechnical and pavement engineering systems. In this paper, the drainage performance of RCA, No. 4 gradation used in a French drain system, has been investigated. Physical properties (i.e., abrasion resistance, gradation, absorption, etc.) of RCA were investigated, and a number of permeability (constant-head) tests were conducted. With the permeability test, the effect of fines (less than 75 µm) on the RCA permeability was evaluated. Lastly, accelerated calcite precipitation testing was devised and conducted to evaluate long-term performance of RCA associated with the calcite precipitation that can reduce permittivity of geotextile.

Drainage Performance Evaluation of Reclaimed Concrete Aggregate

Reclaimed concrete aggregate (RCA) is used as replacement or mixed with virgin aggregates to be used in embankments, hot-mix asphalt (HMA), Portland cement concrete, and base/sub-base layers in pavement systems. However, RCA has not received a lot of attention as a drainage media because of low abrasion resistance, which causes excess fines content, and the potential of clogging material on filter fabrics. The performance of RCA as drainage material has not been evaluated by many researchers, and the limited information restricts its use. This paper describes the testing methods used to evaluate RCA as a French drain material; the French drain system collects water runoff from the road pavement and transfers it to slotted pipes underground and then filters through aggregate. RCA was tested for its physical properties including specific gravity, unit weight, percent voids, absorption, and abrasion resistance. RCA cleaning/washing methods were also applied to evaluate the fines removal processes. A petrographic examination was conducted by using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffracation (XRD). The permeability of RCA was also tested using the No. 4 gradation. The results showed that RCA has a high abrasion value, that is, it is very susceptible to breaking down from abrasion during transportation, stockpiling, or placing. The permeability tests show that the No. 4 gradation does not restrict the flow of water; however, the flow rate is highly dependent on the hydraulic system itself.

Runoff Curve Numbers for Simulated Highway Slopes under Different Slope, Soil-Turf, and Rainfall Conditions

AbstractHighway infrastructure is a major non-point source of storm water runoff and associated pollutants. Forty-four simulated rainfall tests were conducted over a turf-covered plot-scale test bed that represented typical highway slopes of 25, 33, and 50%. The two soil-turf combinations were Argentine Bahia over AASHTO A-3 soil (fine sand) and Pensacola Bahia over AASHTO A-2-4 soil (silty fine sand). All the tests were conducted in central Florida, where the weather is subtropical. This paper presents the analysis of curve numbers (CN) obtained from simulated rainfall-runoff data. The CN values for the 24 tests conducted on the Argentine Bahia A-3 soil combination varied from 70.4 to 93.0 with a mean value of 79.6. The CN values for the 20 tests conducted on the Pensacola Bahia A-2-4 soil combination varied from 89.0 to 97.2 with a mean of 94.0. The scatter of the CN values was more for fine sand (standard deviation of 8.31) than for silty fine sand (standard deviation of 2.48). Single factor ANOVA sugg...

Clogging Potential of Recycled Concrete in Road Drainage

Recycled concrete aggregate (RCA) is often used as a replacement or partial replacement of virgin aggregate. Commonly RCA is used in road foundations (base course), embankments, hot-mix asphalt, or Portland cement concrete. However the use of RCA in drainage systems, such as French drains, is currently prohibited in the state for Florida. The primary concerns with using RCA as a drainage media are the fines content and the precipitation of calcium carbonate to cause a reducing in filter fabric permittivity. Not much research has been conducted as it relates to using RCA as a drainage material; this limited information inhibits its use in French drains. This paper describes the investigation of permeability of RCA as a No. 4 aggregate gradation and base course gradation. The effect of excess fines (passing the No. 200 sieve) and the precipitation potential of calcium carbonate have also been studied.

Monitoring Proximity Tunneling Effects Using Blind Source Separation Technique

The recent advances in sensing methods and data acquisition technologies have facilitated the collection of instrumentation data for continuous structural health monitoring (SHM). However, interpretation of raw sensor data, affected by various known and unknown environmental factors in field conditions is a challenging task. Structural systems are usually undetermined due to limited sensor data that are not sufficient for finding explicit relations between system inputs and outputs. This study aims to introduce a data-driven methodology using response-only data for underdetermined structural systems. The Principle Component Analysis (PCA) as a Blind Source Separation (BSS) method has been used to decompose the mixed raw response data into a linear combination of statistically uncorrelated mode shapes of input data. Being a data-driven method, the proposed framework is not limited in application to a specific sensor type. To evaluate the efficiency of the method in practice, the close proximity excavation effects of a new tunnel on an existing tunnel has been considered. The analysis results show that the method is not only able to decompose measurements into excavation-induced and the environment-induced deformations but also the calculated eigen-parameters can be used as excellent indicators of structural behaviors during excavation by visualizing the tunnel lining deformations.