土木工程專業(yè)外文翻譯---土方工程的地基勘察與施工-建筑結(jié)構(gòu)-全文預(yù)覽
【正文】 tion is important to both the designer and earthworks contractor as it provides an opportunity to understand the properties of the soils when tested as outlined above. It can also illustrate the advantages of predraining in some instances. With mixed soils, face excavation may be necessary to accelerate drainage works. CBR testing of boulder clay soils also needs careful consideration, mainly with the preparation method employed. Design engineers need to be aware of this, as it can have an order of magnitude difference in results. Static paction of boulder clay soils is advised as paction with the or rammer often leads to high excess pore pressures being generated – hence very low CBR values can result. Also, curing of pacted boulder clay samples is important as this allows excess pore water pressures to dissipate. 4. ENGINEERING CLASSIFICATION OF SOILS In accordance with the NRA SRW, general cohesive fill is categorised in Table as follows: ? 2A Wet cohesive ? 2B Dry cohesive ? 2C Stony cohesive ? 2D Silty cohesive The material properties required for acceptability are given and the design engineer then determines the upper and lower bound limits on the basis of the laboratory classification and engineering performance tests. Irish boulder clay soils are predominantly Class 2C. Clause 612 of the SRW sets out paction methods. Two procedures are available: ? Method Compaction ? EndProduct Compaction End product paction is considered more practical, especially when good paction control data bees available during the early stages of an earthworks contract. A minimum Target Dry Density (TDD) is considered very useful for the contractor to work with as a means of checking paction quality. Once the material has been approved and meets the acceptability limits, then insitu density can be measured, preferably by nuclear gauge or sand replacement tests where the stone content is low. As placing and paction of the fill progresses, the insitu TDD can be checked and nonconforming areas quickly recognised and corrective action taken. This process requires the design engineer to review the field densities with the laboratory paction plots and evaluate actual with ‘theoretical densities’. 5. SUPPLEMENTARY GROUND INVESTIGATION METHODS FOR EARTHWORKS The more traditional methods and procedures have been outlined in Section 2. The following are examples of methods which are believed to enhance ground investigation works for road projects: ? Phasing the ground investigation works, particularly the labora
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