Expedient Operations
The Army's enhanced mobility allows soldiers and units to cover much larger areas of terrain, resulting in assets being dispersed. The need to protect these assets continues, yet the materials and methods for accomplishing this task have lagged behind other military technologies. Research and development have resulted in methods that are now catching up with doctrine; and military engineers have the expedient tools necessary to protect personnel, equipment, and supplies.
The Army is exploring the various techniques available for improving soil conditions. FMs 5-430-00-1 and 5-410 explain different methods and techniques where expedient paving and surfacing operations can be used in the TO.
In a TO, traffic routes are very important for moving troops and supplies. In a combat area, manpower, materials, equipment, and time are often unavailable for permanent construction so expedient pavements and surfaces are constructed. When determining the materials and methods to use, engineers consider the time available for construction, the required permanency, the type of terrain, and the anticipated type of traffic. Most prefabricated hasty surfaces have short lives and high maintenance outlays, but the ease and speed of construction greatly outweigh the disadvantages when the expedient surface is used as intended. When constructing an expedient pavement or surface—
- Use any method or material that provides a temporary road or airfield.
- Regard an expedient pavement or surface as an emergency measure, not as a permanent installation.
- Use a bituminous surface as an expedient if it meets the criteria for establishing a suitable base, because a bituminous surface's life and capacity can easily be increased by stage construction in depth.
Expedient Pavements and Surfaces
Throughout history, Army engineers have used expedient surfacing and paving methods. The methods used represent creative engineer responses to deficiencies of equipment, building materials, and trained manpower—circumstances that are typical of wartime field construction.
Although communication routes are vitally important in the TO, the overall need for personnel and equipment may greatly reduce the capability to construct these routes during combat operations. Expedient materials and methods have been developed to alleviate this problem. An engineer must choose the material and the method after considering the desired permanency, the time available for construction, the terrain type, the anticipated traffic volume and type, and the future use. As long as an engineer uses sound engineering judgment, he is limited only by his ingenuity in selecting expedient materials and methods. For information on paving and surfacing operations using membranes and mats, see FM 5-430-00-1 .
Materials
14-1. The word expedient is often misleading when used in the military sense. An expedient paving or surfacing operation is any procedure that must be completed quickly and whose end result is temporary. Expedient materials are often divided into the following groups:
- Manufactured materials. Manufactured materials are produced in a commercial factory. Landing mats are rigid or semirigid portable surfaces that interlock to form the surface of an expedient pavement. These structures contribute to the soil's bearing capacity, but they do not protect the soil from infiltration (water that works its way into the soil through the surface). Membranes do not contribute to the soil's bearing capacity, but they protect the soil from losing strength due to infiltrating water. These surfaces are extremely flexible and also control dust. Under certain conditions, some lower forms of bituminous surfaces are considered to be expedient surfaces.
- Natural and nonstandard materials. Natural expedient materials are materials found in nature at the site, such as rock, sand, timber, brush, and soil. Nonstandard expedient materials are materials that are produced for some purpose other than road construction, such as precut lumber, tar paper, sandbags, and bricks. Natural and nonstandard materials can be used to construct pavements and surfaces.
Special Considerations
14-2. Drainage in expedient operations is just as important as it is in standard paving operations. Since most expedient structures have a short design life, consider seasonal factors when examining the need for drainage. When designing drainage structures, consider the—
- Probability and intensity of precipitation.
- Anticipated storm duration and the use of alternate routes if the planned road is blocked.
- Ratio of time, personnel, and materials used in the original construction of adequate drainage facilities compared to those needed to repair and maintain the inadequately designed road or airfield.
- Cost of replacing or repairing the structure if it is damaged or destroyed by storms.
- Possibility of delays during construction.
14-3. Soil stabilization is discussed in FMs 5-410 and 5-472 . Soil-stabilized mixtures can be used as a wearing surface if the surface is expected to withstand very light traffic. Soil stabilization generally improves the existing subgrade soil. It increases the soil's bearing capacity so that the base course thickness can be reduced or the base course can be eliminated entirely. Stabilization also assists in dust palliation and soil waterproofing.
14-4. The future use of the structure should also be considered. Present conditions may dictate using expedient materials to construct a road for which future improvements are planned. The expedient materials should be compatible with those contemplated for improvements, thus eliminating delays caused by removing the old material.
Roads
14-5. Expedient roads are usually constructed as an emergency measure for crossing difficult terrain. Any available material or method that provides a temporary surface can be used. Wet sand, decking from treadway bridges, rocks, rubble, brick, and canvas can be used as expedients. Dust palliatives can be used as a temporary wearing surface or as a base. The importance of subgrade preparation for expedient roads is discussed in FM 5-430-00-2 . The two types of expedient roads are—
- Hasty. Hasty expedient roads are built quickly to last only a few days. They are normally used to cross a terrain obstacle, such as a beach or a marsh. For breaching operations, beach landings, and roadblock detours, hasty expedient roads must be laid rapidly and easily. They are often laid during darkness. Because of these conditions, they must be light, simple to lay, and compact.
- Heavy. Heavy expedient roads are built to last until a durable standard road can be constructed; therefore, they require more time for construction. They are used because of special ground conditions or a lack of standard road-construction material.
Cross-Country Tracks
14-6. Construct cross-country tracks by removing main obstructions with hand tools or mechanical equipment and passing over them with tracked or multiwheeled vehicles. This road can carry heavy traffic in dry weather, although motor convoys cause considerable dust clouds that aid the enemy's observation of military movements. If necessary, limit the use of the route to night operations or add dust palliatives to reduce the chance of observation.
Army Tracks
14-7. Use a portable timber mat, known as an army track (or tread), to help vehicles pass over loose sand or wet ground. Prepare the mat by lacing 9-foot, 4- by 4-inch or 6- by 6-inch timbers together with cable or thread the timbers onto a cable that passes through holes near the ends of the timbers ( Figure 14-1 ). To keep timbers spaced 12 to 14 inches apart, bore a hole at a 45-degree angle to the long axis of each timber and anchor the cables securely at each end. If desired, fill tracks between the timbers with available material to provide traction and a smooth riding surface.
Chespaling Mats
14-8. Chespaling roads are composed of a series of mats that are 6 1/2 by 12 feet or larger. Make the mats by placing small, green saplings (6 1/2 feet long and about 1 1/2 inches in diameter) 3 inches apart and wiring them together with wire mesh or strands of heavy smooth wire ( Figure 14-2 ). Construct a chespaling road by laying mats lengthwise with a 1-foot side overlap at the junction of the mats. The resulting surface is 12 feet wide. Unless a chespaling road is laid on wet ground, it requires periodic wetting down to retain springiness and prevent splitting. This type of road requires extensive maintenance.
Bamboo Mats
14-9. In some areas, bamboo mats can be fabricated and used for roads. Make the mats by splitting and soaking 2-inch bamboo rods, and weave the rods as shown in Figure 14-3 . Keep the bamboo moist while in use. Lay the bamboo mats on the ground with the long dimension perpendicular to the direction of traffic. Stake the mats securely to the ground and wire adjacent mats together. Bamboo mats are excellent for beach roadways and roads out of fords. On firm ground or sand, the mats remain serviceable for 3 or 4 months; on muddy ground or unstable soil, the mats pass as many as 1,500 vehicles before becoming unserviceable.
Sommerfeld Track
14-10. Although the Sommerfeld track is not a standard supply item, it was a British item in World War II and may appear again in TOs. A Sommerfeld track is light, easily laid, and highly suitable for beach roadways in landing operations. It is made of prefabricated wire-mesh netting and steel bearing rods ( Figure 14-4 ).
Construction
14-11. Bend steel bearing rods at the ends to form 5-inch loops so that steel flats can be threaded through them. The rods stretch the netting without affecting its flexibility for rolling. It is better to remove four out of every five transverse bearing rods; otherwise, they bend up at the ends under normal traffic and catch in the undercarriage of vehicles. Bend the removed bars into U shapes and use them as extra pickets. Half-inch wire rope can be substituted for the transverse bars. Use special buckles (six for each joint) to connect the end rods of successive rolls of mesh at the transverse joint, and use pickets to anchor the track. Pickets are supplied with the track—25 percent are heavy and 75 percent are light. The heavy pickets are better to use in loose sand and gravel where traffic is heavy. An assembled, 100-yard track weighs about 2 1/2 tons.
14-12. Flexible 9- by 3-foot duckboards are used with a Sommerfeld track to give it added depth. Lay the duckboards end to end, and secure them with ordinary pickets. In addition to duckboards, anything from burlap to corduroy can be placed under the track to increase its depth and flotation in varying degrees.
14-13. To construct a road with a Sommerfeld track, begin by rolling a mat out on the ground. Place flats and rods, and stake the mat by placing one picket at each overlap of steel flats and at the center of each transverse rod. To stretch the track taut after it is laid, start pickets with their heads slanting toward the center and with the flat over the picket and slightly off the ground. As you drive the picket into the ground, place a rope sling over the picket and pull the picket to a vertical position (this draws the mesh taut). The mesh netting is not strong, so the picket must bear against the steel flats or transverse rods.
Sommerfeld Sandwich
14-14. For soft beaches or underwater, make a Sommerfeld sandwich by enclosing flexible duckboards between two layers of Sommerfeld track. The upper layer of the sandwich enables vehicle tires to grip; the lower layer gives depth and flotation so that the structure remains on the surface of the sand or mud.
Monkton Pack
14-15. A Monkton pack is a Sommerfeld track that is folded in 7 1/2-foot lengths with the steel flats already threaded ( Figure 14-5 ). The main advantage of a Monkton pack is its speed of laying.
Wire Mesh
14-16. Most wire-mesh surfaces are expedient in the strictest sense of the word. Applied directly to the subgrade, they provide passage for a limited number of vehicles for a short time. Longer life can be obtained by proper subgrade preparation, multilayer or sandwich construction, and frequent staking.
14-17. Chicken wire, chain-link wire mesh, cyclone fence, and expanded metal lath may be used as road expedients in sand; but they are unsatisfactory on muddy roads. Increase the effectiveness of these expedients by adding a layer of burlap or similar material underneath to help confine the sand (mandatory with lighter mesh forms, such as chicken wire or cyclone fence). Diagonal wire that is placed across the centerline and attached securely to buried pickets also fortifies lighter meshes. Sandwich-type construction (a layer of wire mesh, a layer of burlap, another layer of wire mesh, and so forth) is often used. Like other road surfaces, the more layers used, the more durable the wire-mesh surface. Wire-mesh expedients must be kept taut to maintain their effectiveness, so picket the edges of a wire-mesh road at 3- to 4-foot intervals.
Chain-Link Wire Mesh
14-18. Chain-link wire mesh ( Figure 14-6 ) is 6- to 10-gauge wire that has 1- to 1 1/2-inch mesh. One of the most common types is cyclone fence, and it is usually laid over a layer of burlap. Thread a 3- to 10-gauge strand of wire through the edges of the mesh, and secure the mesh with pickets at 3- to 4-foot intervals. Round, hairpin-type pickets (2 to 3 inches in diameter, about 30 inches long, and bent to shape) are desirable. Since the width of chain-link wire mesh is normally 6 to 8 feet, lay at least two sections to obtain a width that is suitable for traffic. Ensure that sections overlap at least 1 foot. A disadvantage of chain-link fence is that a single break causes raveling.
Chicken Wire and Expanded Metal Lath
14-19. Chicken wire and expanded metal lath are laid essentially the same as chain-link wire mesh. If 3-foot-wide chicken wire is used, lay the roadway in 5-foot widths with 1-foot overlaps and fasten the sections together with plain wire. One layer of chicken wire is sufficient for lightweight traffic; three layers are required to sustain trucks. Expedient road surfacing made from chicken wire requires constant maintenance.
Heavy Expedient Roads and Pioneer Trails
14-20. Construct heavy expedient roads in the same general manner as ordinary roads. Since heavy expedient roads are often used over muddy and swampy ground, it may be impossible to completely follow normal construction methods. Whenever possible—
- Clear the road location.
- Install drainage facilities.
- Grade the foundation. Crown it from the center or side, depending on the type of road to be laid. If required, give it a transverse slope.
- Lay the expedient material. Ensure that it has good bearing and is fastened in place.
- Construct one-way roads with turnouts every 1/4 mile. If two-way traffic is desired, lay single tracks side by side.
- Maintain the road. Expedient roads require more maintenance than ordinary roads.
- Replace expedient roads with more durable roads as soon as possible.
Mat Roads
14-21. In general, M8 and M9 landing mats can be used for roads as well as airfields. Lay the mats transversely as shown in Figure 14-7 or lay them longitudinally to form a tread-type road.
14-22. Landing mats can be placed directly on the sand in the length and width desired, but burlap or straw underneath the planking greatly improves flotation. The smoother and firmer the subgrade, the better the resulting road. Place mats so that their long axis are perpendicular to the flow of traffic and the panels are locked together. If a width greater than the effective length of one plank is constructed, manufactured, or fabricated in the field, use half sections to facilitate joint staggering. One layer of mat constitutes a hasty road. Laying a second layer of steel mat as a tread-type road over the initial layer further increases the road's effectiveness. When a landing mat is placed directly over a muddy base, use membrane surfacing, brush, or burlap over the base to prevent oozing mud and increase the road's effectiveness.
14-23. Use several layers of mat to construct a heavy expedient road, and lay the panels in each successive layer perpendicular to each other. Prevent the tendency of the mat to curl up at the ends by making an excavation at the edges of the road. The excavation should be about 1 foot deep with a 3-to-1 slope on the side of the excavation nearest the road. Bend the mats to fit the trench, place them in position, and backfill the excavation over them. Secure the mats by one of the following methods:
- Use a curb of logs or finished timber on the outside edge of the road.
- Wire the edges tightly to buried logs that are laid parallel to the road.
- Stake the edges down.
14-24. Landing mats require constant maintenance and can be damaged by tracked vehicles to the point where salvage and reuse are impossible. The mats are very slippery when wet, making them dangerous for moving vehicles.
Plank Roads
14-25. Use plank roads for crossing short sections of loose sand or wet, soft ground. Plank roads last several months when they are well-built and have an adequate base. Planks used for flooring, stringers, or sleepers should be 3 to 4 inches thick, 8 to 12 inches wide, and at least 13 feet long. When desired, rough, unfinished 3- by 10-inch planks can replace the 4- by 10-inch timbers shown in Figure 14-8 .
14-26. Lay stringers in regular rows parallel to the centerline on 3-foot centers. Stagger the joints, and lay floor planks across the stringers. When seasoned lumber is used, leave 1-inch gaps between the stringers to allow for swelling when the lumber absorbs moisture. Spike the planks to every stringer. Place 6-inch-deep guardrails on each side, leaving a 12-inch gap between successive lengths of the guardrail for drainage of surface water. Place pickets along each side at 15-foot intervals to hold the roadway in line. If necessary, place corduroy, fascine, or other expedient cross sleepers on 3- to 5-foot centers to hold stringers in the correct position or to gain depth for the structure. To allow for drainage, construct the base with a transverse slope versus a center crown. Place treads over the floor planks parallel to the line of traffic to produce a smoother riding surface.
Plank-Tread Roads
14-27. Plank-tread roads can be constructed easily and rapidly, and they require less material than ordinary plank roads. Lay sleepers, which are made of 2- by 10-inch material that is 12 to 16 feet long, across the centerline of the road. Embed the sleepers in the ground on 10- to 16-foot centers. The spacing of the sleepers depends on the length of plank available for tread. If the sleepers are more than 2 feet thick or hold the flooring too high off the ground, reduce the amount of spacing so that the flooring can carry the load without bending excessively. Lay flooring planks, 2 to 3 inches thick by 10 to 12 inches wide, on top of the crossties. A 2-inch plank will suffice as road surfacing in most cases; however, a 3-inch plank should be used for extremely severe conditions. Tread sections can be fabricated and laid directly from a truck bed to facilitate placement. Curbs are normally placed on the inside of each tread to allow passage of the narrowest vehicle using the road. Figure 14-9 outlines the construction details for a plank-tread road.
Log-Tread and Log-Plank Roads
14-28. Log-tread roads can also be constructed easily and rapidly with minimum material. To prevent the logs from rolling sideways under traffic, securely spike them to the crossties. The spacing of the crossties depends on subgrade conditions, but it is normally about 3 feet. Use curbs as described for corduroy or tread roads. A log-plank road is a log-tread road with the center filled.
Corduroy Roads
14-29. If timber is conveniently available, a corduroy road can be built over soft ground. Corduroy roads are made by laying logs (split or round) across the centerline of the road. The three general types of corduroy roads are—
- Standard corduroy. A standard corduroy road consists of crossed logs that are laid directly on the ground. This is the most frequently used corduroy road and consists of one layer. To construct a standard corduroy road—
- Place 6- to 8-inch-diameter, 12-foot-long logs adjacent to each other (butt to tip).
- Place 6-inch-diameter logs along the edges of the roadway, and wire or drift-pin them in place.
- Drive 4-foot-long pickets into the ground at regular intervals along the outside edges of the road to hold it in place.
- Fill the chinks between logs with brush, rubble, or twigs. Cover the entire surface with a layer of gravel or dirt to make the surface smoother.
- Construct side ditches and culverts the same as for normal roads.
-
Corduroy with log stringers. This is basically a standard corduroy road that is more substantial and has two layers. Construct it by placing log stringers parallel to the centerline on 3-foot centers, and lay the corduroy over the stringers as described above for standard corduroy. Securely pin the corduroy decking to the stringers, and prepare the surface as shown in Figure 14-10.
- Heavy corduroy. A heavy corduroy road consists of crossed logs and stringers that are laid on sleepers. A heavy corduroy road has three layers. Place sleepers (heavy logs that are 10 to 12 inches in diameter and long enough to carry the entire road) at right angles to the centerline on 4-foot centers. Build a heavy corduroy road with log stringers on top of the sleepers as shown in Figure 14-11 .
14-30. The softer the ground, the heavier the type of corduroy required. T his is the basic rule for determining the type of corduroy road needed. Stringers and sleepers do not increase the bearing capacity of the decking. They serve as a crib to keep the road surface above the level of the surrounding mud. Stringers and sleepers sink into the ground until they reach a stratum that is capable of supporting the load. In other words, they provide depth for a stable structure. On fairly firm ground, standard corduroy is adequate; on soft ground, stringers are needed; and on extremely soft ground, sleepers are required. Portable corduroy mats (made by wiring together 4-inch-diameter logs) can be prefabricated and put down quickly when needed. Corduroy mats are very similar to chespaling mats, but they are heavier.
14-31. The greatest objection to corduroy roads is the roughness of the surface. Gravel, earth, straw, tall weeds, or fine brush can be covered with earth to make the surface smoother. If the foundation is stable and suitable materials are available to construct a thin covering over the corduroy, a corduroy road is a good temporary road. Provide a blanket of earth or gravel to protect the surface if tracked vehicles use the road.
Diagonal Corduroy
14-32. A diagonal corduroy road is simply a modified corduroy road, and it can be used for any type of corduroy road. The only difference in construction is that the corduroy is placed at a 45-degree angle to the centerline. Diagonal corduroy decreases the impact load on the decking because only one wheel at a time comes in contact with a log. It provides for longitudinal and lateral road distribution and is preferred for heavy traffic. However, diagonal corduroy has a higher maintenance factor than typical corduroy roads and also requires logs that are 50 percent longer.
Fascine Corduroy
14-33. A fascine corduroy road is a suitable expedient in swampy or boggy ground where logs or standing timber are not readily available; but quantities of secondary growth, small trees, brush, or saplings are available for binding into bundles. Fascines are used in much the same manner as logs and are built from straight pieces on the outside. Bind bundles tightly every 18 inches with wire or tarred rope. Lay bundles crosswise on sleepers of saplings that are laid parallel to the centerline of the road on 2- to 4-foot centers. Attach wire ties to the sleepers at 2-foot intervals. Lay the fascines as compactly as possible on the sleepers, and pull the wire ties above the surface of the fascines. Then, fasten longitudinal binders of saplings to the fascines and sleepers, and squeeze and tie them together as tightly as possible.
14-34. This construction results in a continuous mat of fascines ( Figure 14-12 ). Place brush, sod, reeds, grass, hay, and/or earth on the fascine mat to form the finished roadway. Wet down a fascine road periodically to keep brush springy and pliable. A fascine corduroy road will carry loads that compare to those carried by a corduroy log road, but a fascine road is harder to construct and requires constant attention and maintenance.
Mats Over Corduroy
14-35. Placing two or more layers of mats over corduroy allows the road to be used as a heavy expedient if the proper construction methods are used. Place the lower layer longitudinally and the upper layer transversely to the direction of traffic. In addition, mats can sometimes be used successfully with other methods.
Pioneer Roads
14-36. Expedient roads are normally constructed when circumstances prevent using standard construction methods. A pioneer road uses standard construction methods, but it is the simplest and most inexpensive type of ordinary road. Location is the main difference between a pioneer road and other roads. It is justified by primitive conditions and low service requirements and characterized by the many changes in grade (a high-maximum grade is acceptable for short stretches). Vehicles may have to be hauled short distances while the grade is being improved; however, do not contemplate building a road that does not meet known service needs.
14-37. A pioneer road has limitations of grade, curvature, and standard of service. It does not allow the indiscriminate choice of excessive grades or curves. Avoid excessive or unnecessary use of long-sustained low grades and the unwarranted use of broken or steep grades. Even though a pioneer road may eventually be abandoned, always build a pioneer road as if it were a permanent means of passage. Ensure that a quality roadbed is established and that the road renders adequate service during its life, whether short or long. If possible, improve pioneer roads by stages rather than abandon them for another route.
Mat Repair
14-38. M8 and M9 mats are flexible and can be rolled toward one side of the runway to permit subgrade repairs. Bombing causes large craters with twisted, warped, broken planks that are separated and disconnected. Create a square or rectangular opening in the mat by removing planks or cut them with a torch. Properly fill and compact the crater in shallow lifts, place replacement planks in the hole of the mat and, if necessary, weld the planks.
Surface Repair With Brick
14-39. Due to the unavailability of materials or a short deadline for opening a surface to traffic, it may be impossible to match the original construction when repairing damaged surfaces. Brick is a very good expedient because repairs last a long time and permit immediate use of the surface. In addition, brick is normally available since it is a widely used building material. Even roads and airfields with extensive crater damage can be successfully repaired with brick as shown in Figure 14-13 .
14-40. Build up the subgrade in the same manner as the original concrete or bituminous surface. Place a 2- to 3-inch sand cushion on the subbase, and grade the cushion to a slight crown. This allows for compacting of the sand cushion and settling of the subgrade when the brick patch is finished and rolled. When available, use an admixture of cement to stabilize the sand cushion. Stretch a line across the center of the hole and set it to grade. Lay the first row of bricks to this line. For best results, set bricks in a herringbone pattern with the stretcher side up. Brush dry cement grout into spaces between bricks to form a seal, and roll the entire patch with a 5- to 8-ton roller.
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