BUILDING AND MAINTENANCE OF FOREST ROADS -TECHNOLOGIES AND EQUIPMENT
SOIL BIOENGINEERING MEASURES FOR HILL AND SLOPE STABILIZATION WORKS WITH PLANTS
RESEARCH AND DESIGN OF EROSION CONTROL AND SANITATION METHODS ON FOREST ROADS AND SLOPES
CONSOLIDATION OF ROAD SLOPES BY MEANS OF FOREST VEGETATION
SOIL EROSION ON SEVERAL LONGITUDINAL SLOPES OF A TRIAL SKID TRAIL OVER A FOUR-YEAR PERIOD (1992-1996)
M. Asmarandei1 and I. Cazan2
1 S.C. Conforest, Romania.
2 National Institute of wood, Brasov Branch, Romania.
After the second world war the keyword was economic reconstruction for all social and political systems in view of the big collapse that had occurred.
The way chosen by the Romanian people was to utilize their natural resources. One of the most important resources was wood whose products became very important to support the economic and social programmes. The major problem was to realize the necessary permanent access to the logging zones replacing the old railway and cableway systems which were insufficient and provided limited access. In 1950 there were only 1455 km of forest roads in the Banmat and Bucovina forests.
Historically the construction of forest roads in Romania began to provide means of transport for timber, as well as other specific equipment, machinery and building materials.
If mechanical equipment was not available, a large number of unskilled manpower remained the only alternative.
Activities in forest roads development
The construction of forest roads by hand was of low quality and slow; in addition, it was very expensive because the major part of the costs were for site organization with vast camps necessary for the numerous workers. The productivity for the various types of work was:
2.0 -4.0 m3/man/day
· rock breaking and removal
0.6 - 0.9 m3/man/day
1.5 -2.0 m3/man/day
· consolidation/brick works
1.0 - 1.2 m3/man/day
In the period 1954-1960 the average length of a forest road was 4.5 km; it was built in two years by about 250 workers for whom 5-6 huttings had to be provided.
At the beginning of 1960, woodworking complexes had been built which brought about the opening up of access to the main timber supply areas by an appropriate forest roads network.
In this period the basic network was built including crossing of the most difficult straits, quays along the rivers Dambovita, Oltet, Lotru, Cibin, Sadu, Sebes, Nera, Cerna, etc. A huge of volume of work was accomplished with rock breaking and removal reaching in certain zones 150-200 m3/m of road.
Technologies and equipment after 1960
The explosive development of technologies led to important changes in this field of forest roads building. The operations carried out up to then by hand were mechanized, heavy-duty machinery was used for earthworks, specific equipment became available.
Initially the machinery was not like modern bulldozers, powergraders, excavators and did not have the most appropriate technical characteristics (mechanical or cable transmission, manual loading) while the trucks with hydraulic system and small capacity (2.0-2.5 t) had not appeared yet.
For rock breaking up to 2 m, carbides and ferro-alloys rods were used; for superstructure, mobile compactors; for construction works, prefab elements of reinforced concrete; and for culverts, prefab concrete tubes.
Despite the unavailability of appropriate technical equipment, the results were remarkable. Productivity increase and up to 1996 on average 450 km of forest roads were built every year.
The year 1996 represents the beginning of a new stage in the development of forest roads building in our country. From 1966 to 1985 the major part of forest roads had been built in Romania using local equipment and machinery, such as:
· Bulldozer S 1300, then S 1500, S 1800 as main equipment for earthworks. Power is 130-180 hp and productivity 20-30 m3/h.
· Powergrader D 145, also for earthworks. The power is 140 hp and productivity 12-16 m3/h.
· Compactor of 10-12 t with good results for heterogeneous materials. Power is 60-80 hp and productivity 14-16 m3/h.
· Mobile compressor for energy production with compressed air at 8-10 atm., necessary for pneumatic hammers, with a productivity of 3-3.5 m/h with 2 hammers.
· Drills and electric drills. This is a complex equipment with a productivity of 9 m/h.
· Excavator Castor (0.6-1.2 cm) used for large front diggings as well as for earth loading on transport means or yards. Productivity 12-28 m3/ha.
· Rock crusher CM 6, very useful to produce and process mineral aggregates for superstructure of macadam type or enrockment of broken stones from local sources at small capacities. The use of local sources resulted in low prices compared to materials obtained from organized quarries at longer transport distances. The power is 65 hp and productivity 3.6 m3/h.
Present technologies used for forest roads construction
The technologies used depend on the technical possibilities and funds available at the moment of forest road construction. Specific technologies are adopted for each type of operation or stage of execution.
Removal of vegetation and vegetative ground
Wood vegetation and shrubs (over 10 cm diameter) are logged and traded by the manager or investor. The shrubs under 6 cm diameter and wood waste are left on the road and removed together with the vegetative soil by the road constructor. Vegetation and vegetative soil from fills over 1.5 m are not removed.
Grubbing of stumps under 20 cm is done with bulldozers, after dislocating them with explosives.
Other operations such as removal of excessive wet ground from the road and construction of necessary drainage are made mechanically or manually. A road tractor is used to remove vegetation from road slopes.
The first operation for earthworks, when moving from the design stage to actual planning on the ground, is stakes marking various road points until the road construction plan is accepted.
Earthworks include the following preliminary operations: staking the earthwork level outside the clearing limits on reference tags nailed to the base of the trees or special stakes to guide the operators or technical staff when checking project implementation.
Earthworks are the main operation, accounting for about 24 percent of the total volume and value in the execution of a forest road in the last ten years.
Technologies and equipment utilized over the last 30 years were bulldozers in a proportion of 35-90 percent of the total. If the soil to be dug is of a mixed type or is a deluvium covering a 1.50 m layer of hard or very hard rock, the use of a bulldozer goes down to 50-60 percent.
The rest of the digging operations are carried out manually and this reduces the speed of execution and increases work costs.
After removing the vegetation debris and marshy soil, connecting sections are built on the fillsides. These are done manually for a width of 80 cm, 1-1.5 m apart, only on cross slopes of more than 30 percent. They are executed from the bottom the way up.
Earthworks are done by bulldozer on 100-150 m sections, at a minimum distance of 3 m, starting from the top of the slope to avoid digging and transport uphill. The dug soil is transported to a maximum distance of 50 m.
All operations that are not made by bulldozer are performed manually, such as digging and finishing of cut slopes. The excavated soil fallen on the basis of the cut slope is removed by bulldozer or power grader to fills or deposits or on the roadsides up to a distance of 50 m.
On less difficult ground with volumes under 2 m3/m, only power graders are used for earthworks. Transport by power grader is effected only up to a distance of 30 m.
The levelling of the road foundation is done both by bulldozer and power grader. If access is not possible to the equipment, the operation is made manually, for instances in areas with excessive humidity.
Compaction of earthworks is executed on the top side of the fills and cuts. Deep compaction at the basis of fills and cuts is done by the digging equipment.
Draining trenches are usually built with power grades. Experiments have been made with special devices mounted on the bulldozer blade to dig a triangle section. In excessively humid zones, after laying the superstructure the finishing is done manually.
Rock breaking work is carried out with explosive and special tools (jack hammer or knife perforator). Due to the specific kind of these operations, it is necessary to adopt special warning measures in order to organize guard and evacuation to prevent accidents.
Storage and utilization of explosive materials, as well as training of personnel and means of transport are the object of special regulations.
The mostly used method is mine holes with pyrotechnical or electric explosion. The depth of the holes is 1-3 m depending on the volume to be dug, the hardness and the layer stratification of the rocks. A motor compressor of 4-6 m3/min. capacity, with two pneumatic hammers and a percussion rotary is used.
For large rock breaking a pneumatically or electro-pneumatically driven cable drill is used.
When special equipment and dynamite and astralite for drilling were not available, a special system was used by which the explosion was caused on the rock surface using ammonium nitrate. With this method, the dislocated rock is thrown around chaotically and causes excessive damage to the environment. So it was forbidden by the forestry authorities.
The dislocated material is pushed by bulldozers into fills, while rock blocks of over 50 kg weight are broken. The rock fills are not compacted.
After completion of the planned diggings, the surface of the road platform and the ditches are built using light explosions or pneumatic hammers.
The type of pavement depends on traffic conditions and type of soil. Local materials from earthworks and rock breaking or from river beds (gravel) are normally used.
National standards set the technical provisions that must be followed in road construction. Due to limited availability of funds and geological and climatic conditions, these norms have not been observed, resulting in poor quality pavements. A practically, this very important problem has been treated superficially limiting the necessary investments.
The pavement is made of 2-3 layers of rock or gravel. Gravel is used as the foundation layer for a thickness of minimum 10 cm and maximum 40 cm. If crushed rocks are not available, the gravel can also be used for the pavement. For the foundation, the gravel is used ungraded with a uniform grit of 15-20 cm. For the pavement, the gravel is graded and stones bigger than 10 cm are crushed.
Gravel is not used for pavements which have to bear heavy traffic because its shape allows water penetration. Crushed gravel gives good results especially when the river stones are hard.
Broken stones can be obtained from:
· rock breaking;
· local quarries organized by the client or contractor;
· quarries organized by specialized units.
For lower layers, polygrits of 5 cm dimension are compacted. For the upper layers, very good results were obtained with a macadam surface of 40-60 cm mixed with finely crushed rock of 8-15 cm and sand of 0-3 mm. This type of pavement is very expensive and is sued for highways or fist category roads.
For second category roads, the pavement is formed of polygrit stone up to 9 cm. The material is very good at reasonable price from local sources or quarries.
Auxiliary work necessary to give road indications and prevent traffic accidents, also imposed by the regulations on labour protection, include:
· signalling plates;
· guiding poles;
· parapets made up of wood or concrete metal.
Modern methods for superstructure consolidation have been used on heavy traffic roads (over 200 000 t/a) of public interest and also in areas where mineral aggregates are scarce. These methods consist of:
· improving the bearing capacity of the roadbed by:
· stabilization with mineral aggregates;
· stabilization with mineral binders;
· consolidation with geonetworks;
· treatment of pavement with bituminous binder:
· asphalt macadam;
· surface treatment;
· dense mixtures of local materials.
Consolidation work must be carried out to prevent damage to the road by water streams or to ensure the stability of sliding slopes. The main materials used are local, especially raw stones from rock breaking or quarries and gravel from riverbeds.
The type of work depends on road category, climatic conditions, available sources of materials and funds. The following work types are carried out at present:
· Enrockments of raw stone blocks, available locally, for protection against floods. The blocks of a minimum weight of 50 kg are placed manually or by crane.
· Gabions of raw stones in boxes with a wire net. Raw stone are used of a weight of up to 25 kg which can be handled manually. This type of work, as well as the enrockments, is laid on fascines to ensure revegetation which at a later stage can contribute to the protection of the river bank.
· Retaining walls with blocks of over 150 kg are placed by crane or manually at 3:1-2:1. The raw stones used are available locally and are used for minimum thickness of 60 cm and a maximum height of 3 m.
· Walls of raw stones and Ml 00 cement mortar up to heights of 5 m. The raw stones are of all dimensions. These walls are flexible, require low cement consumption but need well-skilled manpower.
· Retaining walls of concrete are used when raw stones are not available. The concrete utilized is B 150, is prepared locally or in specialized locations. These walls are expensive if the supply of aggregates or concrete comes from long distances.
· Prefab walls of B 250 of various shapes and dimensions (boxes, lamella elements) are the most expensive ones but can be built rapidly.
To cross watercourses and to drain the waters from the forest area, when it is located in a mountainous region, construction works are necessary, which represent 9.5 percent of the average costs of the roads built up to now. The main types of construction works are:
· Tube culverts of 60-150 cm diameter of precompressed concrete, erected as a cross duct of 12.5 cm length for 60 cm diameter tubes on slopes of minimum 1 percent and maximum 30 percent gradient. On gentle slopes the construction is on a gravel foundation while on slopes with an over 10 percent inclination the foundation is of concrete. The tubes must be placed at least 50 cm under the level of the road platform Construction is carried out with bulldozers to avoid damage to the tubes.
· Slab culverts of 2-4 m width. Under this limit, tube culverts are used; over this limit, bridges.
The superstructure is of prefab beams 0.50 m wide. These works are made at the same time as the road. the operations for the foundation are partially by excavator, using cyclopean concrete, and are finished manually.
Culverts embedded in prefab caissons up to a 3 m width are used rarely; only when rapid execution is required or under heavy traffic conditions.
The connection of the culverts to the embankments is made of concrete or raw stone. The construction of the culverts depends on type, height and sources of materials.
It is recommended to get the concrete from centralized stations but at distances below 20 km, otherwise it is expensive.
The above construction solutions and technologies have been used to build 36.000 km of forest roads over a period of 40 years. Economic constraints due to limited financial resources for forest roads building resulted in a modest development of equipment and machinery since 1970. Considering the situation of forest roads building from 1970 to 1985, a stagnation in the execution rhythm can be noted and the regression continued even after then. In 1970, 1.980 km were built; in 1988, 90 km while in 1989-1990 no new forest roads were built.
Forest roads maintenance
The present forest roads network of 37.000 km for a traffic of 12.000.000 t/a creates special problems. Starting in 1992 ROMSII, VA R.A. is in charge of forest roads management.
Forest road maintenance requires special organization measures and equipment because their surface is mainly of gravel. Since crushed mineral aggregates necessary for bottom valley roads are not available, gravel is used. However, since it cannot be well compacted, it is frequently dislocated during service and thrown away from the road platform.
The second problem is the damage caused by the transport of equipment and machinery.
The stone material is mostly spread out manually, uncompacted. Maintenance of forest roads includes also consolidation and construction works.
Forest roads are also used for skidding by tractor and draught animals and for storing. These operations when carried out in improper conditions damage the pavement and the trenches.
The available technical equipment is limited due to financial constraints. Power graders and articulated tractors are equipped with special blades and are used for both maintenance of the surface and draining of the trenches.
Considerations concerning forest roads construction and maintenance in Romania
The forests in Romania have not received appropriate consideration from a financial and technological point of view although they constitute the main natural resource of the country. The main reasons for the poor conditions of forest roads are:
1. As from 1980, for environmental reasons, roads on mountain slopes of over 60 percent inclination and earthworks of more than 15.000 m3 are forbidden since earthworks, rock breaking and moving of excavated material on the mountains damage the vegetation and clog the watercourses. Apparently this ban seems to be to the advantage of the forest but the consequence is that there is no access to some isolated forest lands or forest stands. This situation has resulted in high costs of logging operations, cultivation treatments, forest management and production of secondary products. Since 1988 forest roads have been excluded from the programme of the centrally planned socialist economy.
2. Through suitable environmental technologies and strict regulations this situation could or can be improved for mountain slope or bottom valley roads. Since the bulldozer was the main equipment used for earthworks, it was concluded that mountain slope roads damage vegetation. If the bulldozer is replaced by an excavator, the concept about this type of road could be modified. However, the excavator was used only in limited areas as digger and loader. In effect this equipment is more complete than the bulldozer because:
· the excavated material is laid down and not pushed towards the mountain slope, avoiding block and large rock movement which causes damage to the vegetation;
· it allows the cleaning and removing of the vegetation layer on about all the road width, as well as removal of the grubbed stumps;
· performs earthworks at a rate of 100 percent;
· executes at the same time compaction and levelling of the platform;
· through the training of operators, costs are comparable to those incurred with a bulldozer.
3. Rockworks (one of the damaging types of work) were done with nitrate ammonium on the rock surface, damaging the forest. Using a cable drill mounted on a tractor to cause the explosion at a depth of 4-6 m prevents damage to the vegetation. The dislocated material is then removed with an excavator.
4. Adoption of the so-called "definitive works" construction solution using concrete elements or prefabs instead of locally supplied materials led to high costs. The choice between the following different methods of work must be made after a strict economic analysis to arrive at lower costs and shorter time of execution:
· consolidations with dry brickworks, large stone blocks of a minimum weight of 25 kg, used on road slopes and river bed and banks;
· consolidation with caissons or parapets fixed on the mountain slope made of wood residues from stump grubbing and stone;
· decks of bridges and slabs of culverts made of locally supply and processed wood; replacement of culverts for ditch draining with wood boxes;
· connection of slob or tube culverts to wood boxes, generally on mountain slopes.
5. Mineral aggregates were brought in from organized gravel pits and quarries at high prices and long distances. The material was supplied at exaggerated monopoly prices - lei 18.000-25.000 per ton compared to the price of lei 10.000-12.000 per ton charged from a locally organized quarry (ROMSILVA or a contractor), to which transport cost of lei 300 per km must be added. A necessary measure is to establish at least two gravel pits in every ranger district, providing also the appropriate equipment and labour. The material is to be used both for the construction of new roads and for the consolidation of old ones. On the other hand, gravel that is used mainly for pavements can be easily dislocated and. in addition, the road is damaged by the heavy traffic due to its poor compactness and water permeability. It is necessary to use only crushed materials.
6. Work organization is an essential element of any investment activity. In road building work organization does not require a large number of operations but it is necessary that it be done carefully to highlight possible risks. The skilled personnel working in isolated sites should be well trained so that the same operator can work on two or three types of equipment in successive stages. This would be to the benefit of the company but he would also receive a higher wage. Accommodation for the workers must be ensured at camps with appropriate bathroom, canteen, club and related facilities. The personnel working isolated should have the possibility to contact the company's managing staff through, for instance, radio stations, so that supplies, equipment functioning and man's health are always under control.
7. Traffic should be allowed on the basis of climatic conditions, rainfall and conditions of the road platform. In Romania forest roads construction is financed from the national budget and their maintenance from forestry taxes. Therefore, it is necessary to draw the attention of the Romanian authorities that a high rate of returns from forest products can only be obtained after the forest roads density has been improved.
In conclusion, the general economic stagnation has influenced also the construction of roads in the forests. The solution is to find the necessary funds and specialists in an effort to establish efficient measures and technologies to realize them.
DEVELOPMENT OF FOREST ROAD EXECUTION
MAINTENANCE AND REPARATIONS - EQUIPMENT DOTATION AND DEMAND