Engineering applications

PURPOSE Engineering uses of soils affect our lives every day. This exercise is designed to encour­age study of different behaviors of soils subject to various construction activities. Site and regional development is very much dependent on the building of roads, houses, factories, stores, airports, embankments, and the uses of soils as source material for gravel, sand, and roadfill. In prepara­tion for this exercise, study pages 46-48 and 91-95 of the textbook. The references will also be valuable in determining the most appropriate engineering applications of soil surveys (Olson and Warner, 1974).

APPLICATIONS Detailed soil surveys made at a scale of about 4 inches to 1 mile show soil areas down to 1 hectare in size. Often, construction sites are smaller, so that additional extremely detailed and deeper borings are needed for design of specific foundations. Soil maps, however, are in­valuable in initial planning of developments and in preliminary selection of sites where more detailed studies can occur. Route selections for roads and pipelines provide good examples where soil maps are useful. When alternative routes are considered, based on soil maps, more detailed special engineer­ing soils studies can be made of the right-of-way. Over time, the deterioration of the roads (Figure 39) and the pipelines is directly dependent on the characteristics of the soils. The design cost to overcome the soil limitations is also dependent on the soil conditions.

With big buildings (Figure 40) standard soil maps are less useful, but initial city planning, excava­tions, and design of new suburbs commonly make considerable use of soil surveys (Olson and Marshall, 1968). Suburbs around New Orleans, for example, often have subsidence and wetness prob­lems. Soil maps have proved to be of great value for planning in the area, and in design of pilings, foundations, and other engineering features to overcome the severe soil limitations (Soil Survey Staff, 1971 ).

Study FAO Soils Bulletin 19 (FAO, 1977) to get an idea of how engineering data mesh with soil survey data. From the National Soils Handbook (Soil Survey Staff, 1978), select engineering uses

of soils that will offer high-performance contrasts for soils in your area of study. Tables 32 to 37 illustrate some engineering applications of soil surveys for shallow excavations, embankments, dikes, levees, small commercial buildings, gravel, sand, and roadfill. From Table 22 (roads and streets) and the soil map of your area, select the best routes for a road and street network into the area. Then use Table 32 to locate the best places for shallow excavations for buildings. Tables 33 and 37 will be useful to locate and design embank­ments and roadfill. Table 34 gives ratings of soils for small commercial buildings. Table 35 will help locate gravel for roadbed and foundation subbase, and Table 36 identifies probable and improbable sources of sand for mixing concrete. The soil names and the "Form 5" evaluations (see Tables 16 to 18) also provide ratings of the soils for various uses.

Coordinate the "engineering applications" with the other aspects of the project work in your study area. Maximum benefits of soil surveys are ob­tained when environmental improvements are interdisciplinary. Thus, soil surveys provide on-site information of a specified determinable reliability, in accord with the detail of the soil examinations and the scale of the map. The soil survey also provides information for planning erosion control, runoff structures, impoundments, drainage, irriga­tion, and other off-site information necessary to contribute to the best design of a community, an industry, a farm, or a development area.

REFERENCES

FAO. 1977. Soil survey interpretation for engineering purposes. Soils Bulletin 19, Food and Agriculture Organization of the United Nations, Rome, Italy. 24 pages.

Olson, G. W. and R. L. Marshall. 1968. Using high-intensity soil surveys for big development projects: A Cornell experience. Soil Science 105:223-231.

Olson, G. W. and J. W. Warner. 1974. Engineering soil survey interpretations. Information Bulletin 77, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca, NY. 8 pages.

Soil Survey Staff. 1971. Guide for interpreting engineering

77

G. W. Olson, Field Guide to Soils and the Environment Applications of Soil Surveys© Dowden & Culver, Inc. 1984

uses of soils. Soil Conservation Service, U.s. Dept. of Agriculture, u.s. Government Printing Office, Washing­ton, DC. 87 pages.

Soil Survey Staff. 1978. National soils handbook. Part II, Section 400, Application of soil survey information,

Procedure Guide. Soil Conservation Service, U.S. Dept of Agriculture, Washington, DC. Reproduced as Cornell Agronomy Mimeo 82-15, Cornell University, Department of Agronomy, Ithaca, NY. About 100 pages.

FIGURE 39/Road deterioration on soils high in clays and silts with a critical plas­ticity index. The photograph was taken in early spring in Ithaca, New York, after frost action had broken up much of the road.

• , ~-!' ~ -:. --~~w. ___ .

FIGURE 40/Beam-support shoring to pre­vent excavation caving in foundation con­struction for a large building in New Or/eans. Many soils in this area are ex­tremely wet and achieve a liquid state during a significant part of the year. Many deep borings closely spaced were necessary for design of these bUildings, and soil surveys have proved to be very useful for planning suburbs and building construction in the outer newer areas of expanding New Or/eans (photo by Ken Olson).

78 / Field Guide to Soils and the Environment

TABLE 32/Soil survey interpretations for shallow excavations (adapted from Soil Survey Staff, 1978).

LIMITS RESTRICTIVE

PROPERTY SLIGHT MODERATE SEVERE FEATURE

1. USDA TEXTURE ICE PERMAFROST 2. DEPTH TO BEDROCK

(IN) DEPTH TO ROCK HARD > 60 40-60 < 40 SOFT > 40 20-40 < 20

3. DEPTH TO CEMENTED PAN (IN) CEMENTED PAN

THICK > 60 40-60 <40 THIN > 40 20-40 < 20

4. USDA TEXTURE SI COS, S, FS, CUTBAN KS CAVE (20-60 IN) VFS,

LCOS, LS, LFS, LVFS, G, SG

5. USDA TEXTURE C, SIC TOOCLAYEY (20-60 IN)

6. SOIL ORDER VERTISOLS CUTBAN KS CAVE 7. BULK DENSITY (G/Ce) > 1.8 DENSE LAYER 8 UNIFIED OL, OH, PT EXCESS HUMUS

(20-60 IN) 9. FRACTION> 3 IN < 25 25-50 > 50 LARGE STONES

(WT PCT) 10. DEPTH TO HIGH WATER

TABLE (FT) + PONDING >6 2.5-6 0-2. 5 WETNESS

11. FLOODING NONE, COMMON FLOODS RARE, PROTECTED

12. SLOPE (PCT) 0-8 8-15 > 15 SLOPE

TABLE 331Soil survey interpretations for embankments, dikes, and levees (adapted from Soil Survey Staff, 1978).

LIMITS RESTRICTIVE

PROPERTY SLIGHT MODERATE SEVERE FEATURE

1. USDA TEXTURE ICE PERMAFROST 2. LAYER THICKNESS (IN) > 60 30-60 < 30 THIN LAYER 3. UNIFIED GW, GP, SW, SEEPAGE

SP, GW-GM, GP-GM, SW-SM, SP-SM, SM,GM

4. UNIFIED GM,CL ML, SM, SP, PIPING CL-ML

5. UNIFIED PT, OL, OH EXCESS HUMUS 6. UNIFIED MH,CH HARD TO PACK 7. FRACTION> 3 IN < 15 15-35 > 35 LARGE STONES

(WTPCT) 8. DEPTH TO HIGH WATER

TABLE (FT) + PONDING APPARENT > 4.0 2.0-4.0 < 2.0 WETNESS PERCHED > 3.0 1.0-3.0 < 1.0 WETNESS

9. SODIUM ADSORPTION RATIO (GREAT GROUP) > 12 EXCESS SODIUM

(NATRIC, HALlC)

10. SALINITY (MMHOS/CM) <8 8-16 > 16 EXCESS SALT

Engineering Applications / 79

TABLE 34/Soil survey interpretations for small commercial buildings (adapted from Soil Survey Staff, 7978).

LIMITS RESTRICTI VE

PROPERTY SLIGHT MODERATE SEVERE FEATURE

1. USDA TEXTURE ICE PERMAFROST 2. FLOODING NONE, RARE, FLOODS

PROTECTED COMMON 3. DEPTH TO HIGH WATER

TABLE (FT) + PONDING > 2.5 1.5-2.5 0-1.5 WETNESS

4. SH RIN K-SWELL LOW MODERATE HIGH SHRINK-SWELL 5. SLOPE (PCT) 0-4 4-8 >8 SLOPE 6. UNIFIED OL, OH, PT LOW STRENGTH 7. DEPTH TO BEDROCK

(IN) DEPTH TO ROCK HARD > 40 20-40 < 20 SOFT > 20 < 20

8. DEPTH TO CEMENTED PAN (IN) CEMENTED PAN

THICK > 40 20-40 < 20 THIN > 20 < 20

9. FRACTION> 3 IN < 25 25-50 > 50 LARGE STONES (WT PCT)

TABLE 35/Soil survey interpretations for gravel (adapted from Soil Survey Staff, 7978).

LIMITS

PROBABLE IMPROBABLE RESTRICTIVE PROPERTY SOURCE SOURCE FEATURE

1 . UNIFIED GW, GP, GW-GM, GP-GM

SW, SP, SW-SM, SP-SM

SW, SP, TOO SANDY SW-SM, SP-SM

ALL OTHER EXCESS FINES 2. LAYER THICKNESS > 36 < 36 THIN LAYER

(IN) 3. FRACTION> 3 IN

(WT PCT) < 50 > 50 LARGE STONES

80 / Field Guide to Soils and the Environment

TABLE 36/soil survey interpretations for sand (adapted from Soil Survey Staff, 1978).

LIMITS

PROBABLE IMPROBABLE RESTRICTIVE PROPERTY SOURCE SOURCE FEATURE

1. UNIFIED SW, SP, SW-SM,

SP-SM GW, GP,

GW-GM, GP-GM

GW,GP, SMALL STONES GW-GM, GP-GM

ALL OTHER EXCESS FINES 2. LAYER THICKNESS > 36 < 36 THIN LAYER

(IN) 3. FRACTION> 3 IN

(WT PCT) < 50 > 50 LARGE STONES

TABLE 37/soil survey interpretations for roadfill (adapted from Soil Survey Staff, 1978).

LIMITS RESTRICTIVE

PROPERTY GOOD FAIR POOR FEATURE

1. USDA TEXTURE ICE PERMAFROST 2. DEPTH TO BEDROCK > 60 40-60 <40 AREA RECLAIM

(IN) 3. AASHTO GROUP

INDEX NUMBER 0-4 5-8 >8 LOW STRENGTH 4. AASHTO A-4 A-5, A-6, LOW STRENGTH

A-7, A-8 5. LAYER THICKNESS (IN) > 60 30-60 < 30 THIN LAYER 6. FRACTION> 3 IN < 25 25-50 > 50 LARGE STONES

(WT peT) 7. DEPTH TO HIGH WATER

TABLE (FT) >3 1-3 <1 WETNESS 8. SLOPE (PCT) 0-15 15-25 > 25 SLOPE 9. SHRINK-SWELL LOW MODERATE HIGH SH RI N K-SWELL

Engineering Applications / 81