Laboratory And Field Investigations To Address Erosion, Volume Change And Desiccation Cracking Of Compost Amended Expansive Subsoils

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Title: Laboratory And Field Investigations To Address Erosion, Volume Change And Desiccation Cracking Of Compost Amended Expansive Subsoils
Author: Intharasombat, Napat
Abstract: Desiccations cracks are formed during drying process of fine grained cohesive soils in summer and these cracks often appear on unpaved subgrades due to direct exposure to sun . These cracks allow surface runoff infiltration into subsoils and eventually weaken adjacent base and subgrade layers . The loss of support from these underlying layers results in both longitudinal and transverse cracks in paved shoulders and pavements . Composting is a successful method of recycling organic waste material into stabilized materials that could be used for erosion control and landscaping applications . Since compost is rich in fibrous material and exhibits moisture affinity characteristics , it is theorized that compost material can be used to stabilize expansive soils in order to control desiccation or shrinkage cracks in them during dry seasons , which lead to considerable reductions in pavement distresses caused by longitudinal and transverse cracks . In order to verify the compost stabilization process , a comprehensive research study was conducted at four distinct test sites near Stephenville , Lubbock , Bryan and Corpus Christi cities of the state of Texas , respectively . Composts comprising of biosolids , dairy manure , cotton burr , cow manure , feedlot manure and wood compost were considered for stabilizing local expansive soils of these four sites . Laboratory studies were first conducted on the compost materials and compost amended soils to address their volume change and strength behaviors . These studies were used to establish compaction moisture content and dry unit weight conditions for the construction of compost amended covers for further field verification studies . In field investigations , a control plot with no composts as cover and several test plots with Compost Manufactured Topsoils (CMTs ) as cover materials were designed and constructed . Both quantitative and qualitative data was collected from moisture and temperature sensors embedded in test plots , digital imaging related surface cracking studies , elevation surveys , visual observations of paved shoulder crack patterns and vegetation growth on the plots . The collected data was analyzed with statistical comparison t -tests , which indicated that majority of compost test plots showed that they had lesser moisture and temperature variations than those of the Control Plots . This indicates the ability of composts to insulate soils from surficial temperature changes and thus maintain uniform moisture levels in the subsoils . Majority of CMT plots constructed at four sites were able to retain moisture contents close or above the initial compaction moisture contents . This resulted in lesser desiccation cracks in CMT test plots . The reduction in desiccation cracking was attributed to the presence of fibrous materials in composts , which serve as natural reinforcements in the CMTs . Thus , the CMTs were able to withstand tensile forces generated from drying of the subsoil . Other recommendations related to CMT types and field compaction densities as well as erosion potentials of the test plots are explained . Causes for pavement distress resulting from both shoulder and subsoil cracking are identified and potential mitigation methods using compost stabilization techniques are described .
URI: http : / /hdl .handle .net /10106 /186
Date: 2007-08-23

Citation

Laboratory And Field Investigations To Address Erosion, Volume Change And Desiccation Cracking Of Compost Amended Expansive Subsoils. Available electronically from http : / /hdl .handle .net /10106 /186 .

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