Comprehensive and international coverage is achieved by an expert team, including geologists, engineers and architects. Packed with information prepared for a wide readership, this unique handbook is also copiously illustrated.
The volume is dedicated to the memory of Professor Sir Alec Skempton. Various definitions of 'clay' are explored. Clay mineralogy is described, plus the geological formation of clay deposits and their fundamental materials properties. World and British clay deposits are reviewed and explained.
New compositional data are provided for clay formations throughout the stratigraphic column. Investigative techniques and interpretation are considered, ranging from site exploration to laboratory assessment of composition and engineering performance.
Major civil engineering applications are addressed, including earthworks, earthmoving and specialized roles utilizing clays. Traditional earthen building is included and shown to dominate construction in places.
Clay-based construction materials are detailed, including bricks, ceramics and cements. The volume also includes a comprehensive glossary. This synthesis report will be of special interest to pavement engineers and pavement construction and maintenance personnel responsible for portland cement concrete PCC pavement joints.
Still pertinent information from NCHRP Synthesis 19 , as well as new or updated information in the areas of joint design, construction, and maintenance are included. This report of the Transportation Research Board records the state of the practice with respect to the design, construction, and maintenance of PCC pavement joints. In addition, information on joint materials and sealing, the control of water on and in pavements, and the evaluation of pavement joint performance is provided.
Soft Clay Engineering and Ground Improvement covers the design and implementation of ground improvement techniques as applicable to soft clays.
This particular subject poses major geotechnical challenges in civil engineering. Not only civil engineers, but planners, architects, consultants and contractors are now aware what soft soils are and the risks associated with development of such areas. The book is designed as a reference and useful tool for those in the industry, both to consultants and contractors.
It also benefits researchers and academics working on ground improvement of soft soils, and serves as an excellent overview for postgraduates.
Review all previously identified haul roads and flattened slopes to determine if they involve impacts not disclosed by existing environmental documentation. If the needed area extends beyond that approved for construction or may affect an environmentally sensitive area, consult with the district or regional environmental office.
Before removal or corrective operations, determine the method of payment: If the contractor requests the removal of slides and slipouts to be paid for as extra work, obtain this request in writing. When the resident engineer decides this removal should be paid as extra work, record this decision in the change order memorandum. Then process a change order for an ordered change or extra work. When payment is by item price for roadway excavation, measure the additional quantities and enter them on appropriate source documents that clearly identify the limits of the slides or slipouts.
Any applicable method or combination of methods of compensation may be used to pay for removing slides or slipouts. Decide where the contractor should deposit the material resulting from slides and slipouts.
When practicable, use all the material for embankments or for flattening slopes or contour grading. Take before-and-after photographs of the slide area. In addition, the resident engineer must perform the following steps: Make sufficient measurements to verify the proper start of slopes.
Make sufficient spot-checks to verify the correct slope tolerances. Check the slope rounding for compliance with the contract. While the top of the slope is still reachable with equipment, decide whether the contractor should do additional slope rounding or contour grading. Ensure that the construction of any special items for erosion control complies with the contract.
Ensure that all top-of-slope or toe-of-slope ditches will drain. Ensure that embankment widening complies with the contract plans for installing guard railing. Examine slopes for material that blasting has shattered or loosened. Order the removal of this material. The following are some of the factors to analyze when determining whether there will be an unplanned surplus or deficiency of roadway excavation: Determine adequacy of the amount of embankment estimated for subsidence of original ground, considering different field conditions than those the design engineer anticipated.
Calculate variations of slopes. Even within specified tolerances, slope variances can significantly affect quantities. Be alert to differences between pay quantities and the actual amount of roadway excavation as a result of curve correction. On some projects, this difference can significantly affect a surplus or deficiency of material. Decide whether the planned grading factors shrinkage or swell need to be adjusted based on actual conditions.
The factors may be adjusted in any way the resident engineer judges to be appropriate. Appropriate judgments are based on the following: Previous experience.
Measurement of definable portions of excavation and resulting embankment. In-place densities in excavation compared to in-place densities in embankment. Keep adequate measurements and records to support payment.
Also, discuss with these experts any viable alternatives for stabilizing the area. Advise the contractor of the situation, and work with the contractor to determine the payment method for implementing the desired alternative.
Prepare and issue a change order, if necessary. In consultation with the geotechnical engineer, direct the contractor to conduct a foundation investigation, which may include digging test pits, drilling test borings, and performing foundation bearing capacity tests. This additional work will be paid as extra work. Before fine grading begins, order any necessary additional excavation. Enter in the daily report any orders to increase excavation, and enter sufficient data in the appropriate records to support additional payment.
Pay for additional quantity by measuring such quantity and including it in the appropriate contract records when no extra work is involved. Observe fine grading to ensure compliance with requirements for grade and culvert beddings.
When slurry cement backfill is used, ensure that it is adequately fluid and is placed so that it completely fills the area around the culvert. One of the advantages of slurry cement backfill is that it provides adequate support on the underside of pipes where compaction of ordinary backfill material is difficult.
If backfilling steel culverts, reinforced concrete, or other metal products, ensure the contractor adds only nonchloride admixtures to slurry cement backfill to accelerate the setting time. Chloride-containing admixtures, used to hasten curing, increase the corrosion potential of the steel or reinforced concrete structure.
In addition, slurry cement backfill or controlled low-strength material cannot be used as structure backfill for aluminum or aluminized steel pipe culverts. Ponding alone is not permissible because it does not give uniform or adequate consolidation. Pressure jets must be inserted at the bottom of the backfill material at close, uniform intervals.
Prohibit the use of any compacting equipment or methods that may displace or damage structures or otherwise adversely affect foundations or adjacent embankments. Order compaction tests except for slurry cement backfill to ensure compliance with the contract. Also, determine the frequency of such testing, ensuring sufficient frequency to determine compliance with requirements. At the beginning of backfilling, take sufficient tests to establish the amount of effort required to attain the required compaction.
Ensure the contractor places compacted impervious material where erosion of backfill material or seepage through backfill material may occur.
This approach is particularly important at culvert inlets. Ensure the contractor places pervious backfill material as specified. When imported material is used as structure backfill for metal products such as steel pipe, culverts, or reinforced concrete, the imported backfill must be at least as noncorrosive as the native soil material.
Consequently, the special provisions should specify corrosive parameters for the imported fill that are less corrosive than that of the native soil. This requirement applies to imported soil, lightweight aggregate fill, and controlled low-strength material. Contact Materials Engineering and Testing Services for assistance with corrosion recommendations. Also, verify that the contractor fills voids between rocks in each layer with earth or other fine material.
Record such observations in the daily report. Ensure the contractor does not place rocks, broken concrete, or other solid materials larger than 4 inches in areas where piles are to be placed or driven. During hillside construction or where the section changes from embankment to excavation, ensure that benching into existing material is adequate for proper keying of embankment material to original ground. Decide whether benching should exceed 6 feet.
If widening eliminates the need for end dumping from above, increase the benching width to provide room for compacting equipment. Advise the contractor accordingly, and measure the additional excavation for payment. Observe end dumping and prohibit its continued use as soon as normal embankment methods can be used. Ensure the contractor removes from embankment areas all debris from clearing, unless the special provisions allow otherwise.
In heavy grading operations, small gullies and canyons may be filled with loose material during pioneering and haul road construction. During this phase, close observation is necessary so that such areas can be recorded for future correction.
During embankment construction, measure the cross-fall to ensure it does not exceed specifications. Ensure embankment slopes comply with specified tolerances. Ensure surcharges and settlement periods comply with contract requirements. The contractor may choose to use wetting agents, provided no detrimental effects result.
Test at the frequency necessary for control. Take into account the uniformity of the material and the uniformity of the particular operation. Generally, if the operation is uniform and well within specifications, testing frequencies may be decreased. For nonuniform operations, borderline results, or both, increase testing frequencies. Observe compaction testing to ensure it complies with contract requirements.
Advise testing personnel of the specific limits of the testing area. If the contractor chooses to excavate basement material to facilitate compaction, examine the underlying material before the area is backfilled. Decide whether the layer of material below the excavated basement material should be compacted. In general, if sufficient loose material exists to allow settlement of subsequent layers, order compaction of the underlying material by change order.
When material is to be paid for by the ton, ensure there is sufficient moisture testing to determine pay quantities. Ensure the contractor submits the necessary documents covering possible local material sources. During placement of SEG, the resident engineer should ensure that the product has been installed correctly by adhering to the following installation requirements: SEG shall be placed directly on a cleared surface along the alignment to the limits shown on the plans.
The surface to receive the geogrid or geotextile, immediately prior to placing, shall conform to the elevation tolerance and cross slopes as specified in the plans. The subgrade to receive the SEG must conform to the compaction and elevation tolerance specified in Section SEG must be handled and placed in accordance with the manufacturer's recommendations and pulled taut to form a wrinkle-free mat on the prepared surface.
Borders of rolled out geogrid or geotextile must be overlapped a minimum of 2 feet in the direction as ordered by the resident engineer. All roll ends must be overlapped a minimum of 2 feet in the direction of the spreading of the aggregate subbase material.
The geotextile or geogrid must be cut to conform to the curves. A minimum overlap of 1. The overlap must be held in place by staples, pins, or piles of fill of the materials to be placed on the geotextile or geogrid, or as directed by the resident engineer. Construction equipment must not operate directly on the geogrid or geotextile.
A minimum of 6 inches of fill cover is required prior to operation of construction vehicles atop the geotextile or geogrid. The amount of SEG placed on subgrade must be limited to that which can be covered with aggregate subbase or base material within 72 hours. Special care must be taken in the handling of geogrids manufactured from polypropylene at temperatures at or below 0 degrees Fahrenheit.
Stockpiling of materials directly on the SEG is not allowed. Once a sufficient working platform has been constructed, all remaining materials must be placed and compacted in accordance with special provisions and the Standard Specifications. A minimum of 6 inches of fill material must be maintained between the geotextile or geogrid and the equipment to prevent damage to the geotextile or geogrid.
Until this sufficient working platform has been constructed, compaction must be achieved by using either smooth wheel without vibratory action or rubber-tired rollers. Sheepsfoot or other types of compactor equipment employing a sheepsfoot shall not be used. Excessive turning of vehicles must not be allowed on the aggregate subbase or aggregate base material placed directly over the geotextile or geogrid.
Areas of geotextile or geogrid damaged beyond repair during placement must be covered by a new geosynthetic covering. The overlap from the edge of the damaged area must be a minimum of 3 feet.
Geotextile or geogrid must be laid at the proper elevation and alignment as shown on the plans or as directed by the resident engineer. Geogrid must be oriented such that the roll length runs parallel to the roadway alignment.
Intermittent inspection of grading, blasting, and compaction of roadway structural section. Benchmark inspection of placement of structure backfills, embankment, shoulder backing, subgrade geosynthetic and foundation preparation for embankment and roadway.
Intermittent sampling and testing of material and compaction measurement of embankment within feet of bridge abutments. Benchmark sampling and testing of imported borrow and relative compaction of material where specified. Check the accuracy of these calculations. Also check whether slope rounding and quantities for contiguous ditches as shown in the Standard Plans have been included.
Before beginning work, check the accuracy of original ground elevations using slope stake locations. It may also be necessary to take field cross sections or run profile lines to check original ground elevations. This formula is approximately correct. Due to its simplicity and substantial accuracy in the majority of cases, it has become the formula in common use. It gives results, in general, larger than the true volume. When the earthwork center of mass centroid of the area of cut or fill is not centered about the roadway, and the alignment is in curvature, the actual volume calculated is not correct since the true distance between the end area centroids will differ from the distance along the centerline.
In this case it may be necessary to adjust excavation volumes for curvature in order to properly account for earthwork. In many cases this is not necessary since the eccentricities about centerline of the earthwork mass tend to equalize themselves over the route.
Using data furnished by the Geotechnical Unit, the designer must check the characteristics of the material to be excavated or placed in embankments. The values shown in Exhibit 5. Roadway excavation is typically measured in the original, undisturbed position.
The specifications must clearly state the place and method of measurement because almost all materials change volume in their movement from cut to fill.
Excavated common material will expand beyond its original volume in the transporting vehicle but will typically shrink below the excavated volume when compacted into the fill.
To illustrate, 1 cuyd [1 m3] of earth in the cut may use 1. This, of course, depends on its original density and the compactive effort applied. This difference between the original volume in a cut and the final volume in a fill is the shrink. Excavated solid rock placed in a fill typically occupies a larger volume. This change in volume is the swell. When the voids in the rock embankment become filled with earth or other fine material, the volume in the fill will just about equal the combined volumes in the two source locations.
For light soil excavation and for fills constructed on swampy ground subject to settlement, the shrink may range from 20 to 40 percent or even greater. For moderate soil excavation, the shrink ranges from ten to 25 percent.
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