옛날에는 인력(人力)으로 수로(水路)를 만들었으나 기계(機械)의 발달(發達) 및 임금(賃金)의 상승(上昇)에 따라 기계화(機械化) 시공(施工)이 경제적(經濟的)으로 유리(有利)하게 되었으며 앞으로 이런 현상은 더욱 가속(加速)될 것이다. 수로(水路)의 기계시공(機械施工)은 굴착, 정리(整理), 포장(鋪裝)으로 나누어지며 굴착은 수로(水路)의 단면(斷面)을 대략적인 형태(形態)로 만드는 것이고 정리(整理)는 포장(鋪裝)을 할수 있게 .수로(水路)의 사면(斜面)과 바닥을 정확한 모양으로 다듬는 것이다. 정리(整理)의 정밀도(精密度)에 따라 포장용(鋪裝用) 재료(材料)의 양(量)이 크게 좌우(左右)된다. 자동정리기(自動整理機)는 종래의 것이 $20{\sim}40mm$의 표면(表面) 요철(凹凸)이 생기게 하나 현재(現在)는 ${\pm}6mm$의 정도(程度)까지 가능(可能)하다. 현재(現在)의 자동기계(自動機械)는 1인(人)의 운전원(運轉員)이 1일(日) $1,000{\sim}2,000m^3$까지 굴착 정리(整理)를 할수 있다. 콘크리트 포장(鋪裝)은 인력(人力)비빔으로 할때 1일(日) $2m^3/day$의 양(量)도 어렵고 로타리 믹서를 써도 $20m^3/day$ 정도(程度)이나 콘크리트 뱃치 푸랜트로 하면 $100{\sim}500m^3\day$가 가능하다. 그러나 대형(大型) 포장기(鋪裝機)를 사용(使用)하면 1일(日) 대형(大型) 수로(水路) $300{\sim}1,000m$를 포장(鋪裝)할수 있다. 수로(水路)의 기계시공(機械施工)은 콘크리트 포장(鋪裝) 두께를 균일(均一)하게 하므로써 콘크리트 비용(費用)을 최대(最大)로 절감(節減)하며 포장(鋪裝)의 품질(品質)을 좋게한다. 수로(水路)의 기계시공외(機械施工外)에도 많은 새로운 기계(機械)들이 사용(使用)되고 있으며 이러한 기계(機械)의 활용(活用)이 기술발전(技術發展)에 크게 기여하게 될 것이다.

One of most important problems in the Monsoon Asia today is the production of rice paddy to meet the needs of the ever increasing population. Diversemeans are being employed to meet this demand, both by increasing productivity of existing farm land and by bringing further areas into cultivation. The primary step in either field is to ensure that there is sufficient moisture in the soil to suit the paddy, and at the same this means that excess moisture has to be drained off the land, while in others irrigat ion has to be employed to bring sufficient water to an area. In view of the fact that the project comprises a huge amount of earthwork, it can be carried out by extensive use of construction machinery in order to shorten the period. As farm ditch has a comparatively small section with shallow cutting depth, inaddition, there is lack of access road in the field, the excavation equipment with bulldozer or tracter-shovel (backhoe) type are not applicable because there are mostly adapted for the excavation of deep and wide section. Mini-backhoe with its bucket width not larger than 0. 3m, and width of blade not larger than 1. 00m seems to be more adaptable. About 80% of excavation of ditch section will be done by the machinery while the other 20% of excavation together with the finishing of the section are supposed to be done by man-power. The embankment of ditch section can be compacted by the crawler of backhoe when it is moving along the ditch for excavation. However, Lowland paddy field in the Monsoon Asia are made particulary in rain season, therefore, heavy machinery is not easy excavation for ditch. It is very important to know exact ground support power of the working site and select machines with corresponding ground pressure. Ground support power is variable subject to quality and water content of soil and therefore selection of machines should be made duly considering ground condition of the site at the time of construction works. Farm ditches dug and compacted by mannual labar are of poor quality and subject to destruction after one or two years of operation. On the other hand, excavation and compaction by bulldozer is not practical for ditches. Backboe is suitable for slope land, but this is required cycle time of bucket excavation and dumped out. If a small-scale farm ditch trencher adaptable to lowland paddy field is invented, such a machine could greatly accelerate the massive construction work envisaged in many countries and thus significantly speed up the most difficult part of irrigation development and management in Monsoon Asia.

This report summarizes the findings of investigations and studies conducted through fieldtrips and an opinionnaire over a period of 11 months from July 1978 to May 1979 on various problems involved in hydraulic and hydrological phases of 12 large-scale comprehensive agricultural development project, Pyeongtaek-Kumgang, 1st stage and 2nd stage of Yongsangang, Kyungju, Gyehwado, Sapgyocheon, Imjin, Changryung, Miho, Namgang and Nakdonggang which are either completed or imdrocess of implentation for rural modernization in Korea.

The weathered granite soil involves problems in its stability in soil structures depending upon the reduction of soil strength due to the water absorption, crushability, and content of colored mineral and feldspar. As an attemt to solve the problems associated with soil stability, the crushability of weathered granite soil was investigated by conducting tests such as compaction test, CBR test, unconfined compression test, direct shear test, triaxial compression test, and permeability test on the five soil samples different in weathering and mineral compositions. The experimental results are summarized as follows: The ratio of increasing dry density in the weathered granite soil was high as the compaction energy was low, while it was low as the compaction energy was increased. The unconfined compressive strength. and CBR value were highest in the dry side rather than in the soil with the optimum moisture content, when the soil was compacted by adjusting water content. However, the unconfined compressive strength of smples, which were compacted and oven dried, were highest in the wet side rather than in soil with the optimum moisture content. As the soil becomes coarse grain, the ratio of specific surface area increased due to increased crushability, and the increasing ratio of the specific surface area decreased as the compaction energy was increased. The highest ratio of grain crushability was attained in the wet side rather than in the soil with the optimum moisture content. Such tendency was transforming to the dry side as the compaction energy was increased. The effect of water on the grain crushability of soil was high in the coarse grained soil. The specific surface area of WK soil sample, when compacted under the condition of air dried and under the optimum moisture content, was constant regardless of the compaction energy. When the weathered granite soil and river sand with the same grain size were compacted with low compaction energy, the weathered granite soil with crushability had higher dry density than river sand. However, when the compaction energy reached to certain point over limitation, the river sand had higher dry density than the weathered granite soil. The coefficient of permeability was lowest in the wet side rather than in the optimum moisture content, when the soil was compacted by adjusting soil water content. The reduction of permeability of soil due to the compaction was more apparent in the weathered granite soil than in the river sand. The highly significant correlation coefficient was obtained between the amount of particle breakage and dry density of the compacted soil.