【正文】 夠的空間用來(lái)堆放材料。 低可塑性含礫粘土中的巖芯萃取率相當(dāng)好（典型的超過(guò) 90%）。 專家們都建議在 靜壓法取樣和回轉(zhuǎn)鉆進(jìn)后進(jìn)行 深取樣孔的開挖，所開挖區(qū)域的地下水狀況將對(duì)深取樣孔開挖的可行性起到?jīng)Q定作用。 土的工程特性測(cè)試不但價(jià)格昂貴而且歷時(shí)長(zhǎng)（等同于加州承載比的 5 個(gè)點(diǎn)的測(cè)試 amp。該過(guò)程要求設(shè)計(jì)工程師評(píng)價(jià)擊實(shí)試驗(yàn)區(qū)域的總體密度并估計(jì)現(xiàn)場(chǎng)真實(shí)的“理論密度”。被擊實(shí)含礫粘土的硬化相當(dāng)重要，因?yàn)橥恋挠不瘜⑹箍紫端畨毫οⅰＴS多上述低可塑性含礫粘土表現(xiàn)出與時(shí)間相關(guān)的含水量變化特性。 ◆ 土樣測(cè)試的準(zhǔn)備方法必須被明確規(guī)定，而且試驗(yàn)應(yīng)在指定試驗(yàn)室進(jìn)行。其必須在取樣區(qū)域安裝排水邊界以及水坑邊界或借用鉆孔以減少土樣的含水量。對(duì)于許多冰漬土或含礫粘土（混合土）的難點(diǎn)在于其描述與工程性質(zhì)測(cè)試的評(píng)價(jià)。 取樣孔對(duì)于恢復(fù)適當(dāng)尺寸的土樣以及觀察碎屑巖在卵石、漂石中所占比例來(lái)說(shuō)應(yīng)該是適當(dāng)?shù)??；靥畈牧媳仨毐３忠欢ǖ暮?，既不能太濕?dǎo)致土體不穩(wěn)定也不能太干以致不能被充分壓縮。這些冰漬土或含礫粘土主要表現(xiàn)為低可塑性而且還含有從粘土到漂石的不同粒徑顆粒。 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 clay soils (especially those with intermediate type silts and fine sand matrix) have been rejected at the selection stage, but good planning shows that they can in fact fulfil specification requirements in terms of paction and strength. The selection process should aim to maximise the use of locally available soils and with careful evaluation it is possible to use or incorporate ?poor or marginal soils? within fill areas and embankments. Fill material needs to be placed at a moisture content such that it is neither too wet to be stable and trafficable or too dry to be properly pacted. High moisture content / low strength boulder clay soils can be suitable for use as fill in low height embankments (. 2 to ) but not suitable for trafficking by earthwork plant without using a geotextile separator and granular fill capping layer. Hence, it is vital that the earthworks contractor fully understands the handling properties of the soils, as for many projects this is effectively governed by the trafficability of earthmoving equipment. 2. TRADITIONAL GROUND INVESTIGATION METHODS For road projects, a principal aim of the ground investigation is to classify the suitability of the soils in accordance with Table from Series 600 of the NRA Specification for Road Works (SRW), March 2020. The majority of current ground investigations for road works includes a bination of the following to give the required geotechnical data: ? Trial pits ? Cable percussion boreholes ? Dynamic probing ? Rotary core drilling ? Insitu testing (SPT, variable head permeability tests, geophysical etc.) ? Laboratory testing The importance of ?phasing? the fieldwork operations cannot be overstressed, particularly when assessing soil suitability from deep cut areas. Cable percussion boreholes are normally sunk to a desired depth or ?refusal? with disturbed and undisturbed samples recovered at intervals or change of strata. In many instances, cable percussion boring is unable to perate through very stiff, hard boulder clay soils due to cobble, boulder obstructions. Sample disturbance in boreholes should be prevented and loss of fines is mon, invariably this leads to inaccurate classification. Trial pits are considered more appropriate for recovering appropriate size samples and for observing the proportion of clasts to matrix and sizes of cobbles, boulders. Detailed and accurate field descriptions are therefore vital for cut areas and trial pits provide an opportunity to examine the soils on a larger scale than boreholes. Trial pits also provide an insight on trench stability and to observe water ingress and its effects. A suitably experienced geotechnical engineer or engineering geologist should supervise the trial pitting works and recovery of samples. The characteristics of the soils during trial pit excavation should be closely observed as this provides information on soil sensitivity, especially if water from granular zones migrates into the fine matrix material. Very often, the condition of soil on the sides of an excavation provides a more accurate assessment of its insitu condition. 3. SOIL CLASSIFICATION Soil description and classification should be undertaken in accordance with BS 5930 (1999) and tested in accordance with BS 1377 (1990). The engineering description of a soil is based on its particle size grading, supplemented by plasticity for fine soils. For