The main body of dike construction is flood control dike. In order to save the project cost, many construction units directly use local materials. However, with the passage of time, due to complex factors such as dike materials and natural environment, some problems have been left over for a long time, and there will be many dangers in flood season, which is difficult to clean up.
First, the common problems and treatment in dike construction
1, resulting in a gap. Problems often occur in dike construction. If these problems are not dealt with seriously, it is very likely that virtual soil will be formed in the operation section, so side ditches and fences will appear. Once the side ditch and side wall appear, it is necessary to dig out the fill in a certain range of the side ditch and side wall, and then lay the soil in layers. In the construction stage, these fills can be combined with the fills on both sides by using the slope, so that the slope gradient can be kept between 1: 3 ~ 5. It is worth noting that the number of rolling passes should be appropriately increased in the filling part of the boundary ditch and the boundary wall.
2, rigid building junction. Backfill soil on both sides of the building must ensure the concrete strength during construction. When filling the embankment, the surface of the building must be wetted first, and then covered with soil for compaction. However, the thickness of soil should be consistent with the height of mud, and attention must be paid to laying soil and compacting it after the mud is dry. If the soil is paved after the mud is dried out, contact infiltration and erosion will occur at the junction of buildings, which is extremely unfavorable to the quality control of dike engineering.
3. Overhead floor. In the process of quality control of dike engineering, if there is height difference between working sections, it is easy to produce large pieces of accumulated soil. Therefore, if there is a height difference between working sections, it is necessary to adopt the slope connection method. What needs to be emphasized here is that the slope gradient should generally not be steeper than 1∶3. The construction unit must manage the construction process in a unified way, equip the soil leveler to participate in the leveling operation, and uniformly spread and roll the soil. The construction unit should strictly control the large particle size of soil materials. If conditions permit, large clods with particle size exceeding 10cm should be broken first to prevent the phenomenon of overhead layer.
4. Compaction of soil materials.
(1) paving thickness. Every kind of rolling machine has certain influence depth limit, and the thickness of paving soil, whether too thick or too small, has great obstacles to the quality control of dike engineering. If the paving thickness is too thick, it is meaningless to increase the rolling times, because the embankment surface is still loose downward, so in order to meet the engineering requirements of the embankment surface, the ultra-thick soil layer must be dug before rolling to ensure the smooth progress of the project.
(2) Carry out soil rolling test. Different design departments have different requirements for the dry density or compactness of fillers. Therefore, in order to ensure the rationality of the construction, the construction unit will conduct 1 on-site rolling test with designated soil materials and compactors before the construction.
In small and medium-sized dike projects, it is generally difficult to control the water content of soil strictly according to the optimal water content. Therefore, for small and medium-sized dike projects, it is necessary to control the natural moisture content of soil according to the actual yard, and then correct the design and construction parameters appropriately through the field rolling test. If the parameters obtained from the experiment are quite different from those in the design, it is necessary to reflect on the effectiveness of technical measures in the design stage.
(3) Rolling construction method is adopted. In the process of construction, special attention should be paid to two geotechnical indexes in the rolling construction method, namely, the optimal water content of soil and its corresponding maximum dry density. The moisture contained in soil often makes the surface of soil particles coated with film water, and the contact surface of soil particles is lubricated by film water, which will reduce the extrusion porosity of compaction test. Even if the moisture content in the soil does not change much, the dry density of the soil will increase, and the compacted soil will become denser and the saturation will inevitably increase.
5, the new and old dike joint
There are many sundries, tree roots and plant roots on the slope of the old embankment at the joint before the joint of the new and old embankments is cleaned layer by layer, which needs to be cleaned before the joint is cleaned layer by layer. If possible, it is best to cut the old embankment slope into a gentle slope of 1 ∶ 3 ~ 5. Then, in order to ensure that the fill at the joint can be well combined, the construction personnel need to clean it layer by layer according to the progress of the fill. If the height difference is relatively large, then you need to slow down properly when going uphill. For the hard clay on the slope of the old embankment, it is necessary to cut the gentle slope or dig a combined groove along the gentle slope to ensure the better connection between the new and old embankments.
6. Choose embankment fill.
According to the particle composition of soil, soil materials can be divided into coarse-grained soil and fine-grained soil. Coarse-grained soil is often used to support prisms, and its ability to resist seepage deformation is low. When the water level is high in flood season, the slope near the backwater is prone to landslide or soil flow damage. Therefore, fine-grained soil is also often used for inclined walls or core walls that play an anti-seepage role. If you don't pay special attention when rolling, it is easy to appear the phenomenon of "spring soil". When selecting soil materials, we should also pay attention to seasonal changes, especially in the dry season. If the plant protection on the embankment surface is not done well, dust will fly at will, which will do harm to the environment. Therefore, when selecting soil materials, we must choose the appropriate construction method according to the local soil quality.
Second, the construction quality management of important engineering parts
1, construction preparation
(1) construction precautions
Before construction, attention should be paid to all kinds of buried pipelines, waste foundations of buildings, wells and other buildings that should be demolished in the construction area, and treatment measures should be studied together with relevant units.
(2) measuring unreeling
Surveying and setting out is very important, because it runs through the whole process of construction, from the preparation before construction to the construction, and then to the completion acceptance after construction, it is inseparable from measurement. How to do a good job in surveying and setting out is a basic test and requirement for surveying technicians. At present, the total station is generally used in the construction control survey of dike engineering, and the construction lofting survey is also equipped with level and theodolite.
(3) Site cleaning
Site cleaning includes vegetation cleaning and topsoil cleaning. Its direction includes the surface of all areas that need to be cleaned in the construction land, such as permanent and temporary works, slag storage and disposal sites.
① Vegetation cleaning
Remove all trees, roots, weeds, garbage and other obstacles in the excavation area with bulldozers and transport them to the place designated by the supervision engineer. Unless otherwise instructed by the supervisor, the vegetation cleaning on the ground surface of the main project construction site must extend to at least 5m beyond the maximum excavation edge line or building foundation edge line (or filling edge line) shown in the construction drawing.
② topsoil cleaning
Use bulldozers to remove all topsoil containing fine roots, herbs and grass in the excavation area, excavate topsoil according to the excavation depth specified by the supervisor, and transport the excavated topsoil to the designated area for storage. Prevent the soil from being washed away. 2. Dike foundation cleaning
In dike construction, dike foundation cleaning is an important hidden project, which should be strictly supervised according to the corresponding regulations; Generally, the scraper is used to remove turf reed roots, tree roots and sundries, surface humus soil, etc. For special parts in projects such as wells and private houses, manual and mechanical cooperation can be used to clean them; For ponds, ditches, crossing lakes and other parts, the water inside should be drained first, and then the silt should be removed; The removed sundries should be far away from the embankment construction site to avoid mixing with the filling soil; After the embankment foundation is cleaned, the filling process can only be carried out after it is checked and accepted by the corresponding quality inspector.
3. Embankment foundation filling
Impurity soil, silt soil and humus soil cannot be used for embankment construction; Whether the soil moisture content is high or low, it should be aired and sprinkled, and the compaction operation can only be carried out after the soil moisture content reaches the optimal soil moisture content; Shear failure of soil layer; In summer construction, the hot weather leads to the rapid evaporation of soil moisture, so the soil should be leveled by machinery immediately after being transported to the embankment to minimize the influence of moisture evaporation on the compaction effect; In winter construction, the cold weather makes the soil easy to freeze, so the frozen soil should be controlled during construction. If the soil layer is mixed with snowflakes, the foundation can be left unfilled.
4. Compaction of embankment foundation fill
After the embankment is filled, it should be compacted. Usually, the scraper is used to compact along the axis, and the same position can be rolled for about 5 times. During rolling, the lap width should not be less than 1/3 of the rolling track. If soil shear failure occurs during rolling, the original fill must be replaced; In the actual field operation, we can also choose the appropriate compaction method and compaction machinery according to the field situation.
Three. Acceptance evaluation of dike project
The core work of engineering quality management is the inspection and evaluation of engineering quality; When evaluating the quality of the unit project, the relevant data should be timely and accurate, which can truly reflect the quality of the unit project; On this basis, the quality acceptance evaluation of the divisional project should be attended by the quality supervision organization, design, supervision and construction unit * * *, and comprehensively refer to the spot check results of the field data and the unit project quality evaluation results.
The quality control of dike project is the quality control of the whole process, and it is an important only way in the construction stage of dike project. The quality of dike engineering depends on the soil quality and compactness of dike, so special attention should be paid to the control of these two aspects in the construction process. However, it should be emphasized that if quality problems are found in construction projects, they must be solved as soon as possible to improve the construction quality of dike projects.
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