how do you test a soil? why it is important?

Answer 1

The are a number of different tests for soils which vary according to the project. Most soils are tested for optimum moisture content and density at optimum m.c. if the soil is going to be used as a structural fill. Since the soil will be a part of the structure, it needs the same quality control as the wood or the concrete used in the structure.

Assuming a significant project scope, assume building a few miles of federal highway through yellowstone, the first thing I would do is consult a geologist to tell me the big picture of the nature of the soils on my site, and especially through my route.

Of course, if this is a single family wood structure, I don't need a geologist. I don't need an engineer. Unless there is a problem. But I digress. Back to soil testing.

The easiest necessary measurement of a soil on your site is pH. Is the soil acidic, neutral or basic? Use litmus paper. Pink or Blue. This matters in some civil projects, as a strong acidic soil will degrade a portland cement structure.

Other testing that you sometimes need is for in sutu density and average fluff for mass haul diagrams. When you are cutting, hauling and compacting millions of cubic yards of material, you have to know the above characteristics for design, measurement and payment. A 0.2 difference in quantity in 2 million yards at $6.00/yd payment means 2.4 million bucks!

Another common test is gradation. For structural fill you want a WELL graded material. Enough fines for compaction, enough rock for structural support. You may want a UNIFORMLY graded material like pea gravel. Gravel used for drain rock would be an example. You don't want any fines for this application.

The actual labrotoray testing methods are pretty basic. You have some muscle, a couple scales, a couple of buckets, water hose, compacting probe, shaker with sized seives and oven with trays, field book, field buckets, data plotting(ACAD, EXCEL, etc.), tape measure and dumpy level.

Another key test, and perhaps most important, is placed compaction. Once a soil has been tested in the lab and the opt. moisture content and max. density has been established, the plans call out a minimum density for structural fill for the placed soils. Typical specification is 95% of optimum compaction for a given soil. Nuclear instruments can measure this in the field non-destructively and are used industry wide.

Another test is the probe test. I use a sawed off sprinkler valve. It is 1/4" in diameter, and I stab it into existing soils to determine resistance for residential footings. If the soil is very stiff, I don't worry. If the probe offers little or no resistance, I better do some more investigating, which means go deeper.

Of couse if I had to situate a footing for a proposed bridge over a river, I would have to drill bore holes in the river bed if I had to construct a pier or two in the river channel. I would test for the soil type and measure the elevations of all soil logs. If the piers were placed on the bank, I would still drill to get a soil profile of the existing conditions unless the bank was solid rock.

Answer 2

the folks before me really covered alot.....before I answered, I'd ask just what your reason for testing is. If your trying to grow grass or a garden and your having no luck, it seems that a local ag extension office could help you. Your soil could be too acidic, or just lacking in some vital part. If your wondering about the condition of the ground for a new building project, a local geotech firm can perform boring tests and give a report of the soil condition and compaction, but this won't be cheap. One of the easiest method to get an idea of just what's down there is to dig a test pit. Find a friend with a backhoe and dig down 5 feet.
A neat source of testing techniques used for simple analysis in 3rd world countries can be found under resources on the main page for Engineers without Borders-USA.

Answer 3

Soil testing done for engineering purposes will expose a number of potential problems and help with foundation design of building. For example, some soils are considered highly expansive, which could lead to expensive repairs. Soft soils, sometimes due to high water content or soil type could result in excessive settleling of foundations.

Answer 4

Testing soil means to collect soil from a place from diffrebt strata of the soil and then make chemical test of it in the laboratory.Its important for knowing whether or not a certain piece of landissuitablefor a certain building purpose.