摘 要
　　
當(dāng)工程場(chǎng)地的處理面積有限且填方工程費(fèi)用大量增加時(shí)，土方工程的地基勘察設(shè)計(jì)與施工已逐漸地變得重要。由于冰漬土以及含礫粘土的提出使土方工程地基勘察方法的綱要比傳統(tǒng)的勘察方法更詳細(xì)。 本文提出“巖土認(rèn)證”觀點(diǎn)以及對(duì)地基勘察與土方工程相結(jié)合的優(yōu)點(diǎn)加以概要說明。

1、引 言
　　
許多愛爾蘭含礫粘土的勘察與再利用評(píng)價(jià)使巖土工程師與道路工程師感到為難。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。大部分本地粘土與淤泥質(zhì)土中包含不同比例的砂、礫石、卵石、漂石。顆粒級(jí)配控制著土體的行為，而且淤泥使土體性質(zhì)易受天氣變化影響。
　　土體含水量隨著地區(qū)不同而不同，從都柏林硬灰黑含礫粘土的7%到中部、西南部或西北部淺灰色含礫粘土沉積物的20%-25%。含礫粘土吸附水的能力建立的較好但土方工程中計(jì)劃的不恰當(dāng)常導(dǎo)致其擴(kuò)大。
　　
一般來說，良好級(jí)配的土體對(duì)于含水量的輕微變大相當(dāng)敏感，將導(dǎo)致強(qiáng)度下降或不適合用作工程回填土。許多含礫粘土（尤其中等淤泥質(zhì)土或良好級(jí)配的砂）在選擇階段已經(jīng)被篩除，但事實(shí)上它們能對(duì)壓縮或強(qiáng)度起到特定的作用。
　　
篩選過程應(yīng)盡量使用本地土體或者回填區(qū)或路堤邊性質(zhì)相對(duì)較差的土體，通過仔細(xì)評(píng)價(jià)應(yīng)加以應(yīng)用?；靥畈牧媳仨毐３忠欢ǖ暮?，既不能太濕導(dǎo)致土體不穩(wěn)定也不能太干以致不能被充分壓縮。
　　
高含水量、低強(qiáng)度含礫粘土適用于低路堤回填（相當(dāng)于2到2.5米的高度）但不適用于沒有使用土工織布隔離與回填層的土方回填工程。因此，土方工程承包商充分認(rèn)識(shí)土體的處理特性相當(dāng)重要，因?yàn)樵S多工程都受到挖掘設(shè)備通行能力的影響。

ABSTRACT
The design and execution of ground investigation works for earthwork projects has become increasingly important as the availability of suitable disposal areas becomes 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 recommendations outlined on its merits for incorporation with ground investigations and earthworks.

1. INTRODUCTION

The investigation and re-use eva luation 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 20-25% for Midland, South-West and North-West light grey boulder clay deposits. The ability of boulder clay soils to take-in 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 re-use 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 compaction and strength.

The selection process should aim to maximise the use of locally available soils and with careful eva luation 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 compacted.

High moisture content / low strength boulder clay soils can be suitable for use as fill in low height embankments (i.e. 2 to 2.5m) 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.