This paper presents the performance of PVD and vacuum consolidation as ground improvement method at the construction of Kayu Agung – Palembang Toll Road. The analysis was based on observation data ...collected between STA 00+000 and STA 09+000. The PVD was installed to a depth where the conus resistance of 80 kPa was achieved. Thus, the length of PVD varies from 5 to 13 m while the actual depth of clay deposit could reach 20 m. As many as 42 settlement plate data were collected and analyzed using Asaoka method to obtain the predicted final settlement, the coefficient of consolidation and the time to reach 90% degree of consolidation. The results were compared with the duration of vacuum consolidation application and the recorded settlement when the vacuum pressure was stopped i.e., when settlement plate recorded no differential settlement in three readings. The duration of vacuum consolidation application generally longer than the t90 predicted by the method and the actual settlement was larger than the predicted final settlement. This study concluded that the variation of the t90 and the magnitude of settlement at t90 have close relationship with the length of PVD and the condition of the soil layer.
Good water drainage from different sources is one of the most important factors that must be considered when designing subways and highways. The research aims to study and analyze the effect of ...heavy, medium, and low rainfall, select suitable materials to drain rainwater from the surface and vertical drains, and evaluate the rutting that appeared on the compacted surface asphalt layer. The methodology of this research includes the laboratory model (prototype model). A laboratory model consisting of typical structure layers of flexible pavement was used in this research with a 2% slope for degradations and changes in the volumetric properties and permeability of the surface and binder layers of the highway section. A wheel truck was manufactured and used for a continuous go-and-forth with the influence of three different rain intensities to identify and simulate the actual situation of highways and roads. The rainfall duration of 30 mm/min rainfall intensity was 90 minutes, and the rain intensity of 60 mm/min had a rainfall duration of 60 minutes. For the rainfall intensity of 90 mm/min, the time of rainfall was equal to 30 minutes. The results obtained from the laboratory simulation model (box model) indicated that the average quantity of infiltrated water produced by the 30mm/min rainfall intensity in the pavement structure is 36.4 % greater than the average infiltration of this water from the 60mm/min intensity and 52% higher than the 90mm/min intensity of rain. The time of surface drainage ending and the ending time of vertical drainage increases when the rain duration is long, even if the rain intensity is low. The rut depth appeared after 2816 wheel load repetitions to increase this depth by 96% after 127 days of load passage under three different rainfall intensities of a different time. The tensile strength was significantly reduced by 17.25%. The TSR values indicate that the mixtures of the surface and binder layers have good resistance to moisture damage.
Waterlogging and salinization are major impediment to the sustainability of irrigated lands and livelihoods of the farmers, especially the smallholders, in the affected areas of the Indus Basin. ...These problems are the result of a multitude of factors, including seepage from unlined earthen canals system, inadequate provision of surface and subsurface drainage, poor water management practices, insufficient water supplies and use of poor quality groundwater for irrigation. About 6.3 million ha are affected by different levels and types of salinity, out of which nearly half are under irrigated agriculture. Since the early 1960s, several efforts have been made to improve the management of salt-affected and waterlogged soils. These include lowering groundwater levels through deep tubewells, leaching of salts by excess irrigation, application of chemical amendments (e.g. gypsum, acids, organic matter), and the use of biological and physical methods. However, in spite of huge investments, the results have in general been disappointing and the problems of waterlogging and salinity persist.
This paper reviews sources, causes and extent of salinity and waterlogging problems in the Indus Basin. Measures taken to overcome these problems over the last four decades are also discussed. The results reveal that the installed drainage systems were initially successful in lowering groundwater table and reducing salinity in affected areas. However, poor operation and maintenance of these systems and provision of inadequate facilities for the disposal of saline drainage effluent resulted in limited overall success. The paper suggests that to ensure the sustainability of irrigated agriculture in the Indus Basin, technical and financial support is needed and enhanced institutional arrangements including coordination among different federal and provincial government agencies to resolve inter-provincial water allocation and water related issues is required.
The relevance of the study is conditioned by the fact that the large-scale irrigation of cotton fields in arid and desert areas of the Turkestan region inevitably leads to the processes of soil ...salinization. Salinity is a global problem for humanity. Soil salinization is associated with drainage problems, improper use of water resources, growing demand for agricultural products, which leads to increased pressure on agricultural land. In this regard, this paper is directed at investigating the soil salinity of the irrigated light serozem in a cotton farm of Southern Kazakhstan (now Turkestan region) under the vertical drainage, which would provide the necessary background for the reconstruction of the collection-drainage system of the whole region, thus contributing to the increasing the net yield and the quality of the row cotton, as well as preventing soil deterioration. The leading method for studying the issues of the article was the dispersion method, according to which the salinity of soils was determined by seasons. The main objectives were studying the dynamics of salts changes seasonally and timely under the vertical drainage and studying the spatial distribution of salts in the cotton-based farm. The results showed that in 2014 there was recorded a positive dynamic of changes compared to 2012. In spring 2014, the area under medium saline soil in the 0-20 cm layer decreased from 79.5 to 57.7 %; the weakly saline soil area increased from 20.5 to 34.6 %. In the autumn and winter periods, the area of strongly saline soils decreased from 25.6 to 14.1 %. The area of non-saline soils was recorded at 7.7 %. The results showed that changes in the amount of the ions, both vertically and seasonally, occur with the transport of salts along with soil profile under the influence of temperature gradients and the level of groundwater, i.e., in spring from up to down, and in autumn and winter, contrary from down to up. The theoretical and practical value of the study lies in the fact that the material for improving, preventing the salinization of soils will lead to an increase in the general level of ecological safety of the region and country in general.
This article discusses dependencies to calculate the vertical drain wells taking into account evaporation inversion. In a zone near the well,where the depth of groundwater level (GWL) is below a ...critical level, the inversion is set as a constant value. In a zone,where GWL is above a critical level, evaporation inversion is linearly dependent on GWL depth which is unknown in advance. Flowing from underlying aquifers has been taken into account. To illustrate the importance of detailed accounting of evaporation inversion in Central Asian climatic conditions, the forecasted recessions of GWL were compared to those calculated using conventional methods. Calculations were made for climatic and hydrogeological conditions of the northern part of Bishkek.
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