Shear Testing in Made Ground - Essay Example

19, April, 2009 Shear Testing in Made Ground Introduction Much development is taking place on old industrial brownfield sites due to the rise of urban regeneration schemes and the need to conserve green spaces in towns and city centres. These presents challenges in liability, risk and costs. Contaminated land specialists are expected to identify and resolve technical issues that arise on the sites during development. Comprehensive investigation of buildings, soil and water environment enables us to identify the potential hazards and develop a range of appropriate remediation solutions. The remedial measures are guided by the quantitative risk assessment, backed up by understanding wider issues of projects, including civil and geotechnical engineering aspects. To assess risks properly, sufficient quality data is critical, so there is a need to carry out extensive sampling and analysis. The aim is to produce remediation strategies which will integrate with the overall engineering objectives. Regulatory bodies such as the Environment Agency and the local planning authorities has developed links with leading remediation contractors to ensure the viability of options in terms of cost-effectiveness and statutory requirements and environmental practices. Remediation involves physical, chemical and biological methods, including soil treatments. Contamination is defined as a coming into contact something so as to make it impure, unclean or corrupt. It emphasizes effect over cause and implies that some measure of decay or corruption has taken place. Contaminated site is defined as the site that poses considerable risk to the human health and the environment. The contaminated soil functions are endangered because of the impacting of contaminant level. In the local contamination assessment, there were problems that were found. The industrial activities landfills, mining sites radiation comprises the different problems of contamination. The extent are estimated 1.5 million contaminated sites from a preliminary surveys across Europe. Remediation would cost 2,000 million Euro per year all across Europe. Wide contamination extents from limited to strongly polluted; from small sites petrol stations, (petrol stations) to mega sites (thousand of hectares each). Our objective for prevention is to avoid deterioration of soil quality, loss of soil functions and water resources degradation. One question is: does relevant legislation apply and protect the soil efficiently? Diffuse contamination is the application of acceptable input levels that is generally sufficient for remedial measures. A remediation according to Risk-based land management is historic local contamination. New local contamination is the contaminant removal as far as appropriate with respect to the natural background. There are other environmental considerations. Asbestos-presence or disposal in structures and the ground, Natural England will further emphasize the ecological considerations in the future work. Noise or air quality issues during the decomposition process. Land use or space for the creation of new inert facilities for disposal of decommissioning waste and preparation of EIA’s, together with sustainability and public perception are other environmental considerations. The total mass evaluation is composed of the nature of contamination. Contamination exists in four phases in the contaminated zone. These are: soil gas, sorbed, dissolved, non aqeous phase liquid or phase separated. Geochemistry partitioning coefficient determines the phases in the saturated Zone. The majority of the mass which is normally 80% is sorbed and phase separated. There are several laboratory testing done to determine contamination. Soil and water testing is one. Other tests include rock, chemical for the effects on construction materials. Contamination Is considered as analytical testing. The pH factor is considered for the tests, together with the organics and inorganics. Metals and asbestos contents are also taken for consideration. Remediation The process of remediation are done in order to counteract contamination. The option of doing nothing for remediation is not viable in modern society. This assessment would indicate the scale of future contamination problems. The current technologies may not be all for the treatment. The sealing scheme comprised of various land remediation and highway infrastructure projects together with reclamation. The construction of a cement bentonite, slurry cut off barrier up to 10 meters deep encircling the site of a perimeter of 3 kilometers anda groundwater abstraction and treatment plant and primary infrastructure for development is done for treatment. The dig and dump is also considered, but landfill tax for contaminated waste in UK Is £32.00 per tone. Special waste tax is £250 per tonne, and the use of small scale sites and the movement of waste requires a license. The screening or the grading or sieving system involves using large plant on site and passing materials through a grader. Another method is remediation is grouting or soil mixing. The basic requirement for this is to add grout mortar to soil to become solid and inert. Chemical reagents are used as a pre post treatment process to complete the mineralization of the target contaminants. Aerobic in bioremediation is where oxygen is several forms is added to the treatment environment. Anaerobic is where nitrate, iron or any other electron acceptor is being added to the treatment environment where the combination is used and is often in pulses. Soil washing uses water to remove contaminants from the soil. The principle of soil washing in separating the most polluted portion from the cleaner portion of the soil by scrubbing it. This process reduces the amount that needs to be cleaned, and we get two fractions of soil, the clean and the polluted. The temperature vary but the science is simple in thermal treatments. Raising the temperature that is high enough to burn chemicals or create vapour. Issues come from the collection of the gas and high energy inputs. Top create a level site to maximize the usage of the land is often needed. Building a vertical wall or a sloping structure would be a good option. As we need to control water, are we suppose to excavate a filling area? We have a number of choices under excavation of area. Diaphragm wall, concrete piles, sheer piling and others can act in a series of ways. It could be gravity, embedded, reinforced soil or hybrid. Piled walls are used to support excavations either permanently or temporary. Basement and shafts can be formed by using piled retaining walls. There are several types of piled retaining walls. The principal varieties are the contiguous pilled wall where adjacent piles are touching, are the most common type of piled wall. These are used where migration of the ground or water between the piles is not a problem. Secant walls would consist of primary and secondary piles. The primary and secondary piles overlap to act as a barrier to prevent the migration of ground water between the piles. The selection of hard or soft, hard or firm, hard secant walls would depend upon different factors, having durability and structural strength in particular. Retaining walls such as piled, enjoy environmental benefits over other excavation support techniques, such as low noise level, minimal vibration, and can accommodate most basement or excavation shapes and maximize basement or excavation size. Diaphragm walls are constructed by excavating the ground with crane- suspended grabs or crane- suspended milling cutter. The excavation of trench processes takes place when submerged under a support fluid which is normally bentonite slurry. The bentonite slurry provides the support and stability of the sides of the trench. The diaphragm wall is formed by filling the excavated trench with concrete which can be reinforced as per requirement. Factors that lead to a diaphragm wall are selected. Deep excavations where other forms of side support are not economic or possible with restricted working space, and stiffness and resistance to deflection are considered. The props or anchors can be minimized and water exclusion is required. The speed of the construction as well as the predictable, reliable performance and a system of work that is safe. There must also be underground cut-offs to control water, and good surface fluid is required. A typical diaphragm wall applications are for the formation of basements and large shafts. Sheet pile walls are constructed by driving steel sheets into an excavation or a slope. The most common use is within the temporary deep excavations. These are considered to be economical because the retention of higher earth pressures of the soft soil is required. They have an advantage in that, and they are driven to depths below the excavation bottom and provide a control to heaving in soft clays or piping in the saturated sands. However, sheet piles are more expensive and less adaptable to hard driving conditions most particularly where the boulders or irregular rock surfaces occur. The easy driving conditions are experienced in clays, sands and clay-sand mixture because of the small displacement of soil. However, they may permit large movements in weak soils and also effective de-watering is required since they do not provide a watertight boundary. Seepage occurs through the interlocks and this can be sufficient enough to cause consolidation of organic soils and silty clay. Sandy soil raveling will not occur when the interlock are tight. But driving sheet piles into loose sand can cause subsidence. The cantilever sheet pile walls are mainly used for temporary excavations of moderate depth. Large earth pressures and deflections may develop are rarely used to retain excavations greater than the depth of 5 meters. This may be excessive where soft or loose soil occur in front of the wall. Stiffer cantilever walls of concrete or steel material, including diaphragm walls may be satisfactory to heights of 12 meters providing the ground is strong enough. The support is totally derived from the passive pressure exerted on the embedded portion of the pile. The deflections at the head of the wall are high and it is not advisable to use cantilever walls when foundations are within the active zone since movement in the retained soil may cause damage. An advantage of cantilever sheet pile walls is that they can be pulled and reused. Following the installation of steel sheet piles a small excavation is made along the wall and the first row of anchors is installed. The trench is made wide enough and the first row of anchors is installed. The trench is wide enough for the anchor installation machine and the excavation-anchor sequence is repeated until the bottom is reached. A well constructed anchor wall undergoes less lateral deflection than braced walls and provide a better control of back slope subsistence. The installation requires a small excavation to allow equipment access. And braced wall installation is often a requirement to excavate below the level of support. Walls are always pre-stressed which essentially removes the slack from the system. The anchors also place the entire soil mass between the anchors and the wall in compression creating a big cavity wall. Remedial processes have been reviewed. Some of which are implemented and others are not. One process of remediation is the use of vertical and/horizontal pipes that are embedded in the soil around the area of the earth which has been contaminated by a spill and the pipes are connected in a closed portable system with a pressure pump in series with an evacuator having a separator and scrubber. The pipes can have a flushing fluid forced into the soil below the area to flush out the contamination, and the other pipe near the bottom of the contaminated soil in the area can be connected to the evacuators for sucking out the contaminated flushing fluid. Part of the flushing fluid is bypassed for removing the contamination there from before being reintroduced into the closed system. The removal of the contamination from the flushing fluid may be by aeration (if the contaminant is volatile and can be released into the atmosphere without contaminating it), reaction with the chemicals and the adsorption with filters. Solvents can also be used for remediation. Solvents are used for flushing fluids .the flushing fluid may be a gas such as nitrogen. But this application is no longer in use. Conclusion WE have seen in the last 20 years an explosion in research and technology development at targeting the remediation of contamination of groundwater and soil. In the recent history, written seminal reports to take stock of the current understanding of subsurface processes that control the extent of contamination and has provided advice on tools, technologies, and methods for assessing and cleaning the hazardous waste sites. This began with the accounting of the effectiveness of pump and treat technologies for cleaning up ground water, and it is still the most common technology today. The burgeoning role of microorganisms in bringing about site cleanup was also the topic of an early review. More innovative technologies have arisen in the last 10 years and have been reviewed in subsequent reports. These include innovations in ground water and soil clean up. The most recent review discusses the effectiveness of the aggressive technologies in the removal of the most recalcitrant contaminant from the complex hydro geologic environments. Thousands of commercial, industrial, and military sites across the country, subsurface materials including groundwater are contaminated with chemical waste. The last decade has seen the growing interest in using aggressive source remediation technologies in the removal of contaminants from the subsurface, but there is limited understanding of the effectiveness of the technology and the overall effect of mass removal on the quality of the ground water. This report, review the suite of technologies available for groundwater to reducing costs. The report proposes elements of the protocol for the accomplishment of the sources remediation that should enable project managers to decide whether and how to pursue source remediation at the sites. The adaptive management concepts, which are the most frequently applied to large-scale river system management. Could in one way or another be easily adopted by the hazardous waste clean-up world as a means of introducing a more risky technology into the cleanup as they are developed. Issues on environments related to water resources span a range that includes restoration actions, allocation and management decisions and different approaches to assign value to non-market, ecological costs and benefits. The intersection of water-based science and environmental policy decisions often brings the issue to the fore. Science is needed to understand complex aquatic or terrestrial ecosystem to make better policy decisions on how to restore or improve the condition, weigh trade-offs from different land use or development options and manage water resources for different purposes, such as critical habitat, recreation, navigation or irrigation. The national Research Council’s Water Science and technology board has studied the water-related environment issues and had published reports that generally fall into the categories of environmental assessment, ecological restoration, and adaptive management. The request for guidance in the environmental cleanup program was prompted in part by the ineffectiveness of current remedies to meet cleanup goals at the major remaining hazardous waste sites. Especially in the high risk sites that are contaminated with recalcitrant chlorinated solvents and metals. Remediating and reaching closure for these types of sites has proved to be elusive in the current technologies. IN addition to the ineffectiveness of many remedies, the struggle with the balance and meet different remediation goals, such as risk reduction, attainment of clean drinking water standards and the complete removal of the source of contamination. References Basile, A.J. Ground contamination remediation Processes. Ground Contamination and Remediation Processes. 18, January 1994. United States Patent. April 19, 2009. . Rappold, Buro. Contamination and Remediation. Contamonation & Remediation. 2005. Buro Happold. !pril 19, 2009. . ecow.engr.wisc.edu/cgi-bin/get/cee/522/park/classprese/systems1_2treatment.ppt www.egr.msu.edu/classes/ene802/soil_washing.ppt. Soil contamination Proposed EEA/ETC contribution to the working group on Soil Contamination European Topic Centre on Terrestrial Environment . http://www.sbe.napier.ac.uk/projects/retwall/help/index.htm http://galiforty.co.uk/infrastructure/remediation/prideparkderby Read More