 The last video in this set of videos is all about compaction. Compaction is about the removal of air from the soil, it's a process that we can intentionally do to the soil to improve its properties. So it's unlike consolidation which is concerned with how water flows out of the soil during loading. Compaction is an intentional process that we can do to the soil to remove the air. Ond oedd yn cael y cyfnodder o'r unrhyw rusiau yw hwnnw, algunos o'r bobl sy'n unrhyw rusiau, mae'r unrhyw rusiau sy'n unrhyw rusiau, a'i cael ei gweld bod yna unrhyw rusiau arni fel yr unrhyw rusiau. Nid yw'r syniad o'r unrhyw rusiau yn y rhaid i wahanol oed, bod y lle mae'r bobl yn y rhaid o'r cyffredin.�oedd yna maith o'r bobl yn y rhaid i wahanol. Ond oed yn cael y rhaid i cefnod o wahanol o'r rych. Ond o ddiniw, wedi cael y gwneud ond yn fwy ziwyr mewn os blikol. Rhaid o greu gwneud o'r gwneud. Rydyn ni'n ddechrau ddiliw. Rydyn ni'n ddiliw mae'n gwneud o'r gwneud yn ddiliw. Felly weithu'n gofyn honno'n ddiliw. Felly efallai chi'n gweld un o'r llwyffau cymhysgwydau hynny, mae'n cael eu cyfrifoedd y cyfrifoedd o'r llwyffau. Ond yn oed, mae hynny'n cyfrifoedd o'r llwyffau yn y cyfrifoedd yma o'r llwyffau ar y cyfrifoedd. Oherwydd ein pethau cymhysgwydau procter ar gyfer y cyfrifoedd cymhysgwydau cyfrifoedd. Y cyfrifoedd cymhysgwydau procter yw'r llwyffau. Yn y cyfrifoedd yn y mod sy'n ddiddordeb ar yr hyn yn, a we use a hammer to compact the soil into the mould. And there's a peryfaisor for the number of blows and the number of layers that you use to put the soil into the mould. But once we've compacted the soil into the mould, we'll take the outer ring, or the upper ring of the mould, and we'll scrape the surface level. And then we'll measure the mass of the soil that's retained in the bottom part of the compaction mould, and because we know the volume of that soil, because the compaction mould has a definite size, we can work out the density. We also then take a sample of that material and measure the moisture content. So we record from the proper compaction test our bulk density and the water content, and we can use those two things to work out the dry density of the soil. Now if we then plot a graph which relates this dry density to water content, we'll get data in a shape that looks something like this. In practice, the data never looks that elegant, but we should find somewhere within our data we have a peak. So the reason why we have an increase in dry density with increasing water content is that we have increasing soil suction in this part of the curve. And we eventually reach a maximum, which we call the optimum water content. So this is the optimum water content, at the maximum dry density, so dry density max. And then after that we have excessive water content within the soil pose, so we start to have a decrease in dry density. So this is quite useful for practice when we're trying to understand what maximum dry density might be possible within our soil for a given water content.