Gravel V2
Frederic Laureano
Gravel (/ˈɡrvəl/) is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentary and erosive geological processes; it is also produced in large quantities commercially as crushed stone.
Gravel is an important commercial product, with a number of applications. Almost half of all gravel production is used as aggregate for concrete. Much of the rest is used for road construction, either in the road base or as the road surface (with or without asphalt or other binders.) Naturally occurring porous gravel deposits have a high hydraulic conductivity, making them important aquifers.
Colloquially, the term gravel is often used to describe a mixture of different size pieces of stone mixed with sand and possibly some clay.[1] The American construction industry distinguishes between gravel (a natural material) and crushed stone (produced artificially by mechanical crushing of rock.)[2][3][4]
The technical definition of gravel varies by region and by area of application. Many geologists define gravel simply as loose rounded rock particles over 2 mm (0.079 in) in diameter, without specifying an upper size limit.[5][6][7][8] Gravel is sometimes distinguished from rubble, which is loose rock particles in the same size range but angular in shape.[9] The Udden-Wentworth scale, widely used by geologists in the US, defines granular gravel as particles with a size from 2 to 4 mm (0.079 to 0.157 in) and pebble gravel as particles with a size from 4 to 64 mm (0.16 to 2.52 in). This corresponds to all particles with sizes between coarse sand and cobbles.[10]
The U.S. Department of Agriculture and the Soil Science Society of America define gravel as particles from 2 to 80 mm (0.079 to 3.150 in) in size, while the German scale (Atterburg) defines gravel as particles from 2 to 200 mm (0.079 to 7.874 in) in size.[11] The U.S. Army Corps of Engineers defines gravel as particles under 3 in (76 mm) in size that are retained by a number 4 mesh, which has a mesh spacing of 4.76 mm (0.187 in).[12][5] ISO 14688 for soil engineering grades gravels as fine, medium, and coarse with ranges 2 mm to 6.3 mm to 20 mm to 63 mm.[13]
Most gravel is derived from disintegration of bedrock as it weathers. Quartz is the most common mineral found in gravel, as it is hard, chemically inert, and lacks cleavage planes along which the rock easily splits. Most gravel particles consist of multiple mineral grains, since few rocks have mineral grains coarser than about 8 millimeters (0.31 in) in size. Exceptions include quartz veins, pegmatites, deep intrusions, and high-grade metamorphic rock. The rock fragments are rapidly rounded as they are transported by rivers, often within a few tens of kilometers of their source outcrops.[16]
Gravel is deposited as gravel blankets or bars in stream channels;[17] in alluvial fans;[18] in near-shore marine settings, where the gravel is supplied by streams or erosion along the coast;[19][20][17] and in the deltas of swift-flowing streams.[21] The upper Mississippi embayment contains extensive chert gravels thought to have their origin less than 100 miles (160 km) from the periphery of the embayment.[22]
In most cases, gravel will be a mixture of various larger rocks, the most common of which would be basalt, limestone and sandstone. The variation created will largely be dictated by the styling intentions for each project, since limestone often displays a brighter finish, whereas sandstone provides a more rustic appearance.[24]
Gravel is a major basic raw material in construction.[25] Sand is not usually distinguished from gravel in official statistics, but crushed stone is treated as a separate category. In 2020, sand and gravel together made up 23% of all industrial mineral production in the U.S., with a total value of about $12.6 billion. Some 960 million tons of construction sand and gravel were produced. This greatly exceeds production of industrial sand and gravel (68 million tons), which is mostly sand rather than gravel.[26]
It is estimated that almost half of construction sand and gravel is used as aggregate for concrete. Other important uses include in road construction, as road base or in blacktop; as construction fill; and in myriad minor uses.[25]
Gravel is widely and plentifully distributed, mostly as river deposits, river flood plains, and glacial deposits, so that environmental considerations and quality dictate whether alternatives, such as crushed stone, are more economical. Crushed stone is already displacing natural gravel in the eastern United States, and recycled gravel is also becoming increasingly important.[26]
In locales where gravelly soil is predominant, plant life is generally more sparse.[36] This is due to the inferior ability of gravels to retain moisture, as well as the corresponding paucity of mineral nutrients, since finer soils that contain such minerals are present in smaller amounts.
Sediments containing over 30% gravel that become lithified into solid rock are termed conglomerate.[6] Conglomerates are widely distributed in sedimentary rock of all ages, but usually as a minor component, making up less than 1% of all sedimentary rock.[7] Alluvial fans likely contain the largest accumulations of gravel in the geologic record.[18] These include conglomerates of the Triassic basins of eastern North America and the New Red Sandstone of south Devon.[12]
Addix 4-Season Compound:
- Lots of grip at low temperatures, good rolling resistance at all temperatures
- Very good puncture protection thanks to RaceGuard and reinforced Carcass
- Black reflective stripe as a visual highlight and for additional Safety in road traffic
THE SPECIAL ONE. G-One Speed is above all a promise of maximum speed! This tire extends the range of use for every road cyclist. It rolls fast on the road, but at the same time safely on unkept cycle paths and gravel roads.
THE CROSS SPECIALIST FOR MUD AND GUNGE. The aggressive tread bites firmly into soft terrain on a cyclo-cross track and also on any wintertime, muddy forest road. For this reason the X-One Bite is available exclusively in a Tubeless Easy version for best performance in difficult conditions.
The race cyclocross tire
- New tread design with all-round properties
- Improved traction in cornering sections and excellent rolling characteristics
- Sleek souplesse construction: Low rolling resistance + high grip through
Super Race carcass as well as very good Puncture protection thanks to V-Guard
- The choice of the German champions (Judith Krahl and Sascha Weber)
Race-oriented semi-slick racer
- Lowest rolling resistance in the X-One range
- Semi-slick design with climbing and braking blocks
- Sleek souplesse construction:
- Low rolling resistance + high grip thanks to Super Race carcass
- High puncture protection thanks to V-Guard
After the group intro meeting, Amelia and I packed our Roves with layers of clothes, sunscreen, two water bottles each, and our lunches and headed out. All that stuff filled my handlebar bag, fanny pack, and a half frame bag. Immediately upon starting, we sighted our first javelina of the trip and then stopped to whiz in some bushes and take off our jackets, as one does at the beginning of every ride.
Day One featured a 29-mile loop with 1,861 feet of elevation gain. At our highest point, just under 5,500 feet, Amelia and I sat in the shade of a tree and ate our lunches. Sandwiches, mandarins, and good ole potato chips fueled our sunny descent. We stopped to take in the views of surrounding mountains, and, in the washes, we pedaled through canyons of rock and tunnels of cottonwoods sporting orange leaves.
Day Three was the most challenging with 55 miles, 4,145 feet of elevation gain, and a few sandy sections. But the challenge was part of the thrill for me. Climbing a mountain pass led to the best views and descents of the trip. A sandy meander through a creek bottom popped us out into a quaint town with a red schoolhouse among towering cottonwoods, wherein Joe waxed poetic about the idyllic scene. Eating our afternoon snacks, we warmed our arms in the sun among squatty trees, seeing no one and hearing no one except the calls of birds and our fellow riders who passed and waved. It was my favorite day. Until we hit pavement.
Unfortunately, the last seven or so miles were along the shoulder of State Highway 82, a well-trafficked two-laner with an okay shoulder. Regardless of the shoulder, it was a shock to be among the bustle of cars, and I was a grouch about it. Amelia pulled me along as she always does. Once at the campsite, a shower, a beer, and a vibrant sunset over Patagonia Lake State Park cured my proverbial saddle sores. On our last night together, our group feasted on chili and chatted around the fire. We may have made it past 8:30 PM before hitting the hay.
The last day of the gravel tour was a choose-your-own adventure. Denny offered several riding options to see new territory or revisit the first loop from Patagonia. All of us chose the former, adventurers as we are. After riding back to Patagonia from the State Park, we headed north toward the Alto Ruins, a ghost town first settled in the early 1900s for mining. While I was too tired to make it all the way to the ruins, we passed some beautiful rock spires. On the way back, we stopped for a quick rest at the Paton Center for Hummingbirds, a shady sanctuary for birds and bikers alike. It was the perfect end to a great bicycle adventure.
Our leaders emailed our group route information two weeks prior to the start of the tour. We used Ride with GPS, a phone app, to navigate the route. Leaders also handed out paper versions on the first day of the tour.
Logistical information, such as airport shuttle options and a bike shop to which you can ship your bike, as well as the start time of the first meeting, come to each registered participant about 60 days before tour departure as well.
Adventure Cycling considers this a Level 4 on their difficulty scale: A tour for someone looking to push themselves on their adventure. Average mileage between 45 and 60 miles per day, with a variety of terrain. Longer mileage days will typically have more rolling terrain, while shorter mileage days will have hilly or mountainous terrain. Average daily elevation gain between 2,500 and 45,00 feet per day, with some days possibly exceeding 4,500 feet in elevation gain."
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