Hey everyone, Currently studying some plans for 3.85 miles of 4 lane on US 35 in Mason County, West Virgina. One area of the project has close to a 110' cut, close to one million yards in that cut alone. I am going through the soil borings to accurately figure machines and excavating the material and at the bottom of the cut the material is titled as 'Claystone'. What is this material? Can you give a nice detailed description of it? I also have noticed that this is at the top of the cut in another place. The order is Claystone, Shale, Sandstone, Claystone. Is it just another term for clay? Any help is appreciated. Thanks!
Claystone is a hardened sedimentary rock composed of extremely fine clay particles. The Unified Soil Classification System categorizes most claystones as having low plasticity, with a liquid limit less than 50. The material does vary in its compressive strength which can dictate the best method of movement for the material. Find and make sure you read/understand the notes in the Technical Specifications of the plans detailing the type of claystone and its particular psi/compressive strength rating. Often times the geotechnical engineer will detail the nature of the particular material types shown in the boring logs. If they’re not there, call the engineer who reviewed/detailed the logs and ask. Some claystones can be excavated with scrapers due to their fragmental nature, and beneath a 70,000lb+ sheepsfoot compactor will easily break down into fines which can easily be finish graded. Most of the more hardened claystones will require blasting to facilitate sufficient fracturing to be easily penetrated by scrapers. Depending on the compressive strength of the materials in their in-situ formation, off the cuff I would recommend drilling a 12’x10’ pattern, load it at a .8 powder factor, touch it off and send in the twins. Haul roads made of any of the materials mentioned will hold up any sized scraper, so there’s no need to run small for haul road integrity. Maintain the cut with a D9 sized dozer equipped with a slopeboard. Claystone fractures too much when cut-slopes are track-walked by even a small dozer to make it look good. But a slopeboard can shave the grade into the slope and make it look perfect. Maintain the fill with the sufficient number of 825’s to handle the production rate of the material. They may fight the shale and sandstone depending on their composition, but should be able to break all those materials down into workable sizes to pass most any highway specifications standards.
Here's a picture of some low psi, fragmented claystone being excavated with scrapers.
Thanks you very much for the great information, the picture is great as well.
In the soil boring legend it gives you different hatched lines and such for different characteristics. It gives you a key for Claystone, Siltstone, Shale, Sandstone, Coal, Limestone, and Conglomerate. It also gives you 12 other keys that are titled as A-1-a, A-1-b, A-2-4, A-4, A-5, A-7-5, A-2-7. Am I missing something somewhere to tell me those characteristics? What are those numbers and letters standing for?
Not sure if this is the same type of soil your talking about but we have a clay that is hard as a rock. It's red just like bricks, in fact they use it to make bricks, but darn near inpossible to dig. scraping with the teeth and giving it all the machine want you will only get 6-8" of cut for ever scoop with the excavator. Breaks off into square like hunks ranging from 4"-18" and takes a dozer running over them to break them apart. Real rough on the bucket teeth too.
They should correspond with footnotes in the boring logs showing the transitions between material types in the profile of the cut. The claystone that Dirtman2007 describes is some of the harder types, which really do require blasting if high production movement of the material is needed. Trying to excavate hard claystone straight from its native state can be done on a small scale, but it’s a bear if you’re trying to get through a lot of it.
Thank you guys, so far unable to find notes that correspond in the logs. I will continue to look.
My next few questions are related to the same project, but may not be completely soil related. In the spec book it talks about Open Graded Free Drainage Base Course. The work is constructing a base course of coarse stabilized aggregate. The quantity is a little over 19,000 CY. My question is: What is the meaning behind Coarse Stabilized Aggregate? It talks about Ashalt Stabilized Alternative and Portlant Cement Stabilized Alternative. First thing that comes to my mind is soil stabilization because I see the portland cement. The reason I think about this is that there is no items elsewhere in the bid tab relating to stabilization. Any help is appreciated there. Also, there is an item titled Subgrade, quantity is just over 28,000 CY. In the plans on the Typical Sections it shows a 6" thickness. In the spec book under material descriptions it says 'Material for subgrade shall be granular material free of particles larger than 3 inches.' A few paragraphs later: Granular Material: 'Granular material shall be considered as natural or synthetic mineral aggregate, such as broken or crushed rock, gravel, sand, or slag. Shale or fly ash shall not be considered granular material. Granular material shall not have more than 25 percent by weight of grains or particles passing the No. 200 sieve and the plasticity index shall not be more than 6. The material must be capable of being compacted to a stable condition. My question being: This material sounds to me it's going to be your typical crushed limestone from a quarry? Does this mean we will have 6" of one Granular Material and than another 4" of this Open Graded Free Drainage Base material? This project is for the West Virginia Department of Transportation, bid date is Tuesday September 23rd. All help is appreciated. Thanks!
Track down some manuals on geotechnical engineering and geomaterials. There are several books available that discuss different geomaterials used in transportation construction; covering all aspects of stabilized materials, mechanistic characteristics of cement based and bituminous-stabilized aggregates, chemically treated clays, rapid stabilization methods, etc. Reading through them will answer most of your questions regarding the different types of materials and their classifications that you’ll see referred to in the technical specifications of transportation project. I often use these types of manuals as reference guides to identify specific geomaterial types, as well as to find equivalent materials to those called for by the design engineer in different transportation projects bid sheets. It’s not uncommon for a geotechnical engineer to be accustomed to working with, or having been trained around a specific material type, say cement stabilized aggregate base (CSAB), and therefore state those materials with set strength parameters as being required for the project. Using the geotechnical notes in the plans to determine the required strength qualities required for the subgrade within the project, I can sometimes find alternative materials that are equivalent in strength, but are lower cost than what the designing engineer specs out. Like flyash/milled asphalt aggregate base combinations (which can be processed on site with a pug mill for low cost) will meet the same geotechnical strength specifications as the CSAB and therefore give a contractor an edge of winning the bid. “What is the meaning behind Coarse Stabilized Aggregate? Approved spec aggregate base coarse, with an approved stabilization chemical added. Often Portland cement, fly ash or lime. “This material sounds to me it's going to be your typical crushed limestone from a quarry? Does this mean we will have 6" of one Granular Material and than another 4" of this Open Graded Free Drainage Base material?” Just going off what you wrote, that sounds correct. Aggregate base coarse cross sections built like that are commonly used to support a finished cementous cross section weighing over 165lbs per cubic foot. Typically 10”-12” steel reinforced concrete with a couple tenths skin of a bituminous material on top for ride quality.
Thank you very much for the info. I will check out the cross sections to see finished elevations vs. the top of the cut/fills to see check this out further.