【正文】 ch deep trial pits on several large road ground investigation projects. The data obtained from these has certainly enhanced the geotechnical data and provided a better understanding of the bulk properties of the soils. It is remended that this work be carried out following pletion of the cable percussion boreholes and rotary core drill holes. The groundwater regime within the cut area will play an important role in governing the feasibility of excavating deep trial pits. The installation of standpipes and piezometers will greatly assist the understanding of the groundwater conditions, hence the purpose of undertaking this work late on in the ground investigation programme. Large representative samples can be obtained (using trench box) and insitu shear strength measured on block samples. The stability of the pit sidewalls and groundwater conditions can also be established and pared with levels in nearby borehole standpipes or piezometers. Over a prominent cut area of say 500m, three deep trial pits can prove invaluable and the spoil material also used to carry out smallscale paction trials. From a value engineering perspective, the cost of excavating and reinstating these excavations can be easily recovered. A provisional sum can be allocated in the ground investigation and used for this work. HIGH QUALITY LARGE DIAMETER ROTARY CORE DRILLING This system entails the use of large diameter rotary core drilling techniques using air mist or polymer gel flush. Triple tube core drilling is carried out through the overburden soils with the recovered material held in a plastic core liner. Core recovery in low plasticity boulder clay has been shown to be extremely good (typically in excess of 90%). The high core recovery permits detailed engineering geological logging and provision of samples for laboratory testing. In drumlin areas, such as those around Cavan and Monaghan, IGSL has found the use of large diameter polymer gel rotary core drilling to be very successful in recovering very stiff / hard boulder clay soils for deep road cut areas (where cable percussion boreholes and trial pits have failed to perate). Insitu testing (vanes, SPT?s etc) can also be carried out within the drillhole to establish strength and bearing capacity of discrete horizons. Large diameter rotary drilling costs using the aforementioned systems are typically 50 to 60% greater than conventional HQ core size, but again from a value engineering aspect can prove much more worthwhile due to the quality of geotechnical information obtained. SMALLSCALE COMPACTION TRIALS The undertaking of smallscale paction trials during the ground investigation programme is strongly advised, particularly where ?marginally suitable? soils are present in prominent cut areas. In addition to validating the laboratory test data, they enable more realistic planning of the earthworks and can provide considerable cost savings. The paction trial can provide the following: ? Achievable field density, remoulded shear strength and CBR ? Establishing optimum layer thickness and number of roller passes ? Response of soil during paction (static v dynamic) ? Monitor trafficability amp。因此，土方工程承包商充分認(rèn)識土體的處理特性相當(dāng)重要，因為許多工程都受到挖掘設(shè)備通行能力的影響。良好級配且含水量為 10%15%的低可塑性土最難進(jìn)行描述與分類。理想地說，土的含水量應(yīng)與其粒徑有關(guān)，而且還有相應(yīng)的級配分析曲線，雖然該曲線不是具有實際應(yīng)用價值。愛爾蘭含礫粘土基本上都屬于 2C 含石粘性填土。當(dāng)土的分類測試（含水量、顆粒級配分析以及阿太堡界限）完成后，才能對巖土數(shù)據(jù)以及工程特性測試計劃進(jìn)行進(jìn)一步的分析。 在冰堆丘地區(qū)，例如在 Cavan 和 Monaghan地區(qū)，地質(zhì)科學(xué)研究所發(fā)現(xiàn)聚合物膠質(zhì)體技術(shù)的 大直徑高質(zhì)量回轉(zhuǎn)鉆進(jìn)已經(jīng)成功地在該地區(qū)非常堅硬的含礫粘土中進(jìn)行深部取樣（靜壓法取樣和取樣孔在該地區(qū)均失敗）。 從監(jiān)督方面來看 (包括地基勘察承包商與咨詢工程師 )，為了反對現(xiàn)場勘察工作重復(fù)，工作重點應(yīng)放在現(xiàn)場巖土工程師或工程地質(zhì)工作者的水平上。 ◆ 結(jié)合現(xiàn)代化儀器設(shè)備，土方工程施工過程中的監(jiān)測變的非常簡單。 ◆ 許多土在篩選及設(shè)計階段被輕易篩除。 大 型地基勘察設(shè)計的特征表明獲得數(shù)據(jù)過程中雙方良好的交流與適應(yīng)非常重要。 低可塑性含礫粘土中的巖芯萃取率相當(dāng)好（典型的超過 90%）。 土的工程特性測試不但價格昂貴而且歷時長（等同于加州承載比的 5 個點的測試 amp。被擊實含礫粘土的硬化相當(dāng)重要，因為土的硬化將使孔隙水壓力消散。 ◆ 土樣測試的準(zhǔn)備方法必須被明確規(guī)定，而且試驗應(yīng)在指定試驗室進(jìn)行。對于許多冰漬土或含礫粘土（混合土）的難點在于其描述與工程性質(zhì)測試的評價?；靥畈牧媳仨毐３忠欢ǖ暮浚炔荒芴珴駥?dǎo)致土體不穩(wěn)定也不能太干以致不能被充分壓縮。 DESIGN AND EXECUTION OF GROUND INVESTIGATION FOR EARTHWORKS PAUL QUIGLEY, FGS Irish Geotechnical Services Ltd ABSTRACT The design and execution of ground investigation works for earthwork projects has bee increasingly important as the availability of suitable disposal areas bees limited and costs of importing engineering fill increase. An outline of ground investigation methods which can augment ?traditional investigation methods? particularly for glacial till / boulder clay soils is presented. The issue of ?geotechnical certification? is raised and remendations outlined on its merits for incorporation with ground investigations and earthworks. 1. INTRODUCTION The investigation and reuse evaluation of many Irish boulder clay soils presents difficulties for both the geotechnical engineer and the road design engineer. These glacial till or boulder clay soils are mainly of low plasticity and have particle sizes ranging from clay to boulders. Most of our boulder clay soils contain varying proportions of sand, gravel, cobbles and boulders in a clay or silt matrix. The amount of fines governs their behaviour and the silt content makes it very weather susceptible. Moisture contents can be highly variable ranging from as low as 7% for the hard grey black Dublin boulder clay up to 2025% for Midland, SouthWest and NorthWest light grey boulder clay deposits. The ability of boulder clay soils to takein free water is well established and poor planning of earthworks often amplifies this. The fine soil constituents are generally sensitive to small increases in moisture content which often lead to loss in strength and render the soils unsuitable for reuse as engineering fill. Many of our boulder