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Work in this paper describes the results of a field and modeling study conducted to investigate the extraction of LNAPL (jet propellant 4, i.e., JP-4, jet fuel) using Prefabricated Vertical Wells (PVWs) at a former air force base. Field testing consisted of 185 operating hours on 25 rows, each consisting of 7 or 8 PVWs. A total of 133 L of free-phase liquid is removed from the subsurface in addition to 467 kg of organics in the vapor phase as a result of volatilization due to the application of vacuum heads exceeding the JP-4 vapor pressure. Monitored field data are used to calibrate a numerical model for investigating the effect of irreducible water content, LNAPL, and gas contents on system performance. Analysis results show that increasing the irreducible water content from 5 % to 20 % decreases the free-LNAPL specific volume from 0.08 m to 0.067 m, which led to reduction in removal efficiency. Under a continuous saturation condition, more wetting fluid (water), traps the nonwetting fluid (LNAPL) in the soil pores, and reduces its mobility, which eventually impedes the LNAPL recovery. Given the model parameters that simulate field conditions, the PVWs show best removal rates in the gas phase. The model results indicated that 292 L of JP-4 can be recovered in 19.5 days (based on 8 h of operation per day) with an effective rate of 1.87 L/h. At the end of 4.25 years of system operation, the maximum benzene concentration is 0.002 ppm. At a gas extraction rate of 10,273 L/min, a maximum concentration of 0.38 ppm in the vapor phase is achieved after 2.5 years of vapor extraction.

Electrical resistivity imaging seeks to reconstruct conductivity model of subsurface water-bearing body for disaster reduction and resource protection. Since its high non-linearity, the inverse problem relying mainly on linear least-square method may inclined to consider much deeper adoption of non-linear algorithm. Ant colony optimization (ACO) is a standard probabilistic algorithm used to find optimal paths. Since the direct application of the ACO is unstable, there are many false anomalies, and prior information needs to be applied according to the laws of physical properties. This study proposed a priori constrained approach to improving ant colony optimization method wherein prior information is included as regularization term in search process. First, we introduce foraging path smoothness into objective function to reduce non-uniqueness. On this basis, smooth constraint of resistivity is added into visibility and inequality constraint is added into pheromone intensity, by which some unnecessary nodes of foraging paths are avoided form selecting by ants. Finally, the strategy of global minimum is introduced in the process of updating pheromone. Forward modeling of each ant selected is parallel calculated via shared-memory computing strategy. Taking into account of those, the direction of global minimum is maintained and the search efficiency is improved greatly, which makes the constrained ACO feasible for the 3-D resistivity inversion. Both numerical experiments and field application is conducted to evaluate this method and illustrate that we can obtain the improved inversion results of subsurface water-bearing body.

This programme involves the study of the technique of using a micro-computer to control a rock drilling machine. The motion of an existing jumbo machine has been successfully analysed. The kinematic control equations are established for any given geometrical configuration. The computer software has been written to demonstrate its feasibility. The needs of hardware implementation are also discussed.

The reliability-based design (RBD) was investigated in this study on the serviceability limit state of steel piles driven in glacial deposits. A database of 42 high-quality pile load tests was used to quantify the uncertainties of the standard penetration test (SPT)—based design methods. A two-parameter hyperbolic model was adopted to represent the measured load–displacement response of a pile, and the load component of the model was normalized with the capacity identified from the pile load test. A statistical analysis was conducted on the performances of 11 different failure load identification methods. The De Beer method was selected due to its low variations and relatively conservative estimation. The measured capacities were compared to predictions from three SPT-based design methods. The statistical properties of the capacity bias, a ratio of the measured to predicted capacity, were evaluated for characterizing the uncertainties of a pile design in glacial deposits. The average of the capacity bias varied from 0.96 to 1.13 with the coefficient of variations ranging from 36.4 to 50.9%. From the pile load tests, probability distributions were fitted to the collected capacity biases and hyperbolic model parameters, and several copulas were evaluated to represent the observed correlations between the two hyperbolic parameters. Lastly, the resistance factors in the RBD were calibrated with Monte Carlo simulations. In the end, a series of resistance factors were developed for an allowable displacement of 5 to 25 mm for three SPT-based design methods. Based on this study, the values of the resistance factors ranged from 0.04 to 0.49, which were largely influenced by the design methods due to their capacity biases and variations.

This paper focuses on short-range modelling and forecasting of aggregate US monthly coal production. The 1976–83 time-series data suggest a multiplicative autoregressive integrated moving average (ARIMA) model to replicate national level monthly coal production. The identified model required 12-month seasonal differencing and has an autoregressive component of lag 1 and a moving average component of lag 12. Model predictions for 1984 were very reasonable when compared with actual production: cyclical patterns were correctly replicated and the deterministic increasing trend was properly identified. The estimated model was enhanced by updating it with data for 1984. Intervention analysis was used to determine the impact of labour negotiations in coal production. Information relative to the identified ARIMA model was then used to model the intervening event of labour negotiations. Intervention modelling produced forecasts for 1984 superior to those identified by the ARIMA model. The mean predicted 1984 US monthly coal production of 1976–84 ARIMA and intervention models were 96.05 and 99.65% of the observed value of 74 178 thousand short tons per month, respectively. Simplicity of the ARIMA and intervention models, the realiability of their predictions, and the ease of updating make them very attractive when compared with large scale econometric models for use in short-term coal production forecasting.

One-dimensional laboratory consolidation test was carried out on compacted tropical black clay (also known as black cotton soil because the cotton plant thrives well on it) treated with up to 16 % rice husk ash (RHA) to assess the effect of compactive effort and curing period on the consolidation characteristics of the treated soil. Specimens were compacted using three different efforts; British Standard Light (BSL), West African Standard, and British Standard Heavy (BSH). Compacted specimen at BSL effort were also cured for 7, 28 and 56 days before being subjected to one dimensional consolidation tests. The gross yield stress increased with increase in RHA content, curing period and compactive effort, ranging from 5 to 26 % between 0 and 56 days curing period and BSL to BSH effort, respectively. The compression index decreased with increased curing periods (15–40 %), increased compactive energy (10–55 %) and increased rice husk ash treatment; while the effect of compactive effort and RHA treatment was more pronounced in reducing the swell index than the curing period. The variation in coefficient of volume compressibility (Mv) decreases with increased compactive effort and curing period irrespective of the loading pressure and RHA content. The Coefficient of consolidation (Cv) generally decreased with increased compactive energy but showed no observable trend with prolonged curing period irrespective of the RHA treatment.