Beneficial Use of Drinking Water Plant Sludge in Utility Cut Backfill

• Main Author: 紀宗男
• Other Authors: 劉明仁
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/82093615332770642952

碩士 === 淡江大學 === 土木工程學系 === 91 === This study was focused on the feasibility of beneficial utilization of drink water plant sludge cake in utility cut backfill. Two main ways of utilization at laboratory stage was evaluated. One was replacement of aggregate backfill using modified and pelletized sludge. A simple method of pelletization for sludge cake was developed using equipments in laboratory. Particles of modified sludge were agglomerated via mixing predetermined amounts of sand, cement and pulverized sludge cake in a drum mixer. After pelletization and gradation adjustment, properties of modified sludge cake could meet current specifications provided by Taiwan Water Supply Corporation (TWSC) and Taipei Water Department (TWD) for aggregate backfill. The other was making controlled low strength material (CLSM) with sludge cake. Pulverized sludge cake was added to make high early strength CLSM and normal CLSM, respectively. For application in high early strength CLSM, effects of sand/aggregate (S/A) ratios and percentages of sludge on its engineering properties were examined. Effects of water/cement (W/C) ratios and percentages of sludge were investigated for application in normal CLSM. Major findings based on the results of this study were summarized as follows: 1.Percentage passed #200 sieve was approximately 90% and the PI value was 16 of plant for drink water plant sludge. The soil classification was grouped into MH, which was a medium-plasticity silty soil, according to the Unified Soil Classification System (USCS) and had a low permeability coefficient of 1.71×10-5 cm/sec. Virgin sludge couldn’t be utilized directly in utility cut backfill because of its poor engineering properties. 2.Modified and pelletized sludge cake could meet gradation requirements of TWSP and TWD specifications. The γd was 1435 kg/m3, CBR value was 2.8 %, and expansion rate was 3.6 % for the sludge before it was modified. Thus, virgin sludge was considered as an expansive and bad soil. After mixing with sand and cement, theγd, CBR values and other properties of modified sludge were effectively improved. 3.For application in high early strength CLSM, workability was increased with higher content of fine aggregate and increase of sludge proportion. However, initial setting time and development of early strength were delayed because of the increase of sludge proportion. Addition of coarse aggregate and limitation of sludge content was recommended when sludge cake is utilized in high early strength CLSM. 4.For application in normal CLSM, workability was increased and compression strength was reduced with increase of W/C ratios and sludge proportion. When proportion of sludge was 30%, best workability was achieved and compression strength of 28-day was ranged between 4.6 and 25 kg/cm2 in this study.