In recent years, many flood disasters have occurred in our country, especially in cities with dense populations and many buildings. Therefore, the construction quality of flood control embankment projects has received widespread attention. In urban water conservancy and flood control projects, the construction quality of flood control embankment projects should be placed in an important position. Only by strengthening the management of project construction quality and strictly controlling construction quality can we improve the construction quality of flood control embankment projects and ensure that flood control projects can survive floods safely.
1 Project Overview
A certain flood control embankment project is distributed on both sides of the bank, with a total length of 3.143 km. The earth dam type is a trapezoidal cross-section homogeneous earth dam. The dam crest elevation is 95-96 m, the dam height is 10-20 m, and the top width is 20 m. The upstream and downstream dam slopes are 1:2, and the slopes are paved with 200 mm first. Thick coarse sand filter layer, followed by M7.5 mortar stone slope protection 400 mm thick. The project completed 142 290 m3 of filling and 28 291 m3 of mortar stone. After the project is completed, it will undertake the task of flood control in the county town on both sides of the strait, prevent floods that occur once in 20 years or less from flooding back into the city, protect the economic construction of the county and the safety of people's lives and property, and protect the city area of ??1.16 km2, population 12,900 people.
2 Material field distribution and material source characteristics
The selection of the soil material field should comprehensively consider factors such as the location of the soil material field, the physical properties of the soil material and the price of land acquisition. These factors directly Affect project construction quality and project cost. According to the design requirements, the compaction degree of the filled clay is ≥0.92, φ≥22, C≥20 kPa, and the permeability coefficient k<1×10-5 cm/s. Three earth material pits were initially selected: one is located on a hillside 600 m to the west of the project, with a ground elevation of 115.9 to 120 m, and is mostly She land; the second is a borrow pit in a nearby brick factory, with a ground elevation of 105 m; the other place is near the entrance of the power station, which is Shedi, with a ground elevation of 105-108 m. In December 2009, detailed exploration and testing work was carried out on all soil fields. The above materials fields are all distributed in the upper part of the secondary terrace. The lithology is clay, silty clay and gravel silt. The main physical and mechanical indicators are: natural water content 23.3 %～24.5%; natural weight 17.7～18.2 kN/m3; maximum dry weight 16.2～16.3 kN/m3; internal friction angle when saturated is 16.42～24.13, when unsaturated is 26.34～29.40, cohesion 55～65 kPa; permeability coefficient 2.47×10-8～9.55×10-8 cm/s; the optimal water content is 22.5%; the compression coefficient is 0.12 MPa-1; the compression deformation is 51～53 (1/100 mm).
The above earth material fields are widely distributed, with a thickness of 5 to 10 m. The reserves and quality can meet the engineering design requirements. The transportation is convenient and the transportation distance is 3 to 4 km.
3 Dam filling construction
3.1 Determination of rolling construction parameters
Before rolling the dam, in order to review and adjust the construction parameters proposed in the design, A rolling test and a relative density test were conducted on the rolled materials. After discussion and research by the technical leadership group of the Engineering Department, the construction parameters were finally determined: the rolling machine is an SD-10T self-propelled vibrating roller, the thickness of the layer is 30 cm, and the number of rolling passes is 8 times, dry bulk density 1.62 kN/m3, moisture content 22.5%, relative density 0.92.
3.2 Dam foundation cleaning
Before excavation, measure and stake out strictly according to the requirements of the drawings. The stake out side line should be 50 cm wider than the design side line (or theoretical filling side line), and the wooden stakes should be driven into place. A good sign. Sprinkle Shuangfei powder on the sideline to guide the excavator operator in excavation, and at the same time provide technical explanation to the operator. During the excavation process, proceed layer by layer from top to bottom. First, remove all trees, weeds, silt, humus soil and other debris within the base surface. When the excavation is close to the base surface, a protective layer is reserved for the base and edges. The slope slope should be appropriately left with margin for manual trimming.
3.3 Embankment body filling construction
After the embankment foundation is cleared to the design elevation and passes the joint inspection, embankment body filling can begin. The construction of this project starts from the lowest-lying part, and the filling method is to spread the soil upward in horizontal layers. First, a 2 m3 excavator is used to dig and load soil materials in the soil yard, and a 20-ton dump truck is transported to the working surface. The material is unloaded using the backward method, and a bulldozer is used to spread the material and unify the warehouse. On the same working surface, the soil is uniformly spread and unified. After rolling, the warehouse surface is basically flat, and the fluctuation difference does not exceed 10 cm. In order to ensure the quality of the filling along the embankment, a margin of 50 cm should be added outside the design edge line. The thickness of the soil layer is controlled by a manufactured ruler. The ruler is placed 5 m away from the front end of the unloading material. The thickness of the soil layer is 30 cm. While leveling the soil, push the old embankment into a step shape to facilitate compaction of the joint surface of the new and old embankments. Because the soil materials are excavated directly from the soil field to reach the dam, the moisture content is generally between 23.3% and 24.5%, so there is no need to sprinkle water during the rolling process. The rolling equipment is an SD-10T self-propelled vibrating roller. The rolling is carried out parallel to the axis of the dam, using the advance and retreat staggered method. The number of rolling passes is 8, and the walking speed is controlled at 2 to 3 km/h. Vibration-free rolling, under-rolling and missing rolling are strictly prohibited. The starting and final rolling of the unit must be rolled 8 times with a certain distance between advance and retreat. Places that cannot be rolled by local vibration must be compacted sequentially with frog-type tamping machines. When making gap treatment for the temporary ramp on the upper embankment that occupies the section of the embankment body, the hardened old soil shall be loosened and compacted in layers according to the filling requirements together with the new soil materials.
3.4 Treatment of the joint between the embankment body and the drainage gate
After the construction of the drainage gate is completed and maintained to 50% to 70% of the design strength, filling construction can be carried out. Before filling the soil, the milk skin, dust and oil stains on the surface of the drainage gate should be removed, and the exposed iron parts on the surface (such as formwork pin bolts, etc.) should be cut off. The remaining outcrops of the iron parts should be covered and protected with cement mortar; when filling the soil, Wet the surface of the building first, then apply mud, spread soil, and tamp it down. The height of the slurry should be consistent with the thickness of the soil. The thickness of the coating should be 3 to 5 mm and should be connected with the lower coating. It is strictly forbidden to spread the soil and compact it after the mud has dried. Clay with a plasticity index greater than 17 is used to prepare the mud, and the concentration of the mud is 1:3 (weight ratio of soil to water). Within a range of 1 m close to the drainage gate, frog-type tamping machines are used to compact the area in sequence.
3.5 Issues that should be paid attention to when filling soil on rainy days
Compact the working surface in time before rain, and make the central bulge slightly tilted to both sides. Clay filling should be stopped when it rains lightly. The clayey soil filling surface should not be walked on when it rains, and vehicles are strictly prohibited. When construction resumes after rain, the filling surface should be dried and repressed. If necessary, the surface should be cleaned again, and work should be resumed in a timely manner after passing the quality inspection.
4 Slope Protection
After the dam body filling construction is completed, a reverse excavator is used to cut the slope. Before cutting the slope, stake out the position of the slope edge (slope top) and cross-section, cut the slope according to the design slope ratio, and reserve 20 cm for manual slope cutting. After cutting, use a broom to clean away the loose soil on the surface. The slope protection method of this project adopts the method of first laying a 20 cm coarse sand filter layer, and then laying 400 cm thick M7.5 mortar stone masonry. The face protection project is an exterior surface project. It is the main part of the project for people to visit and comment on during construction and after completion. The construction must be carefully organized. Before construction, stake out the joint lines and edge lines, drive wooden stakes at the foot and top of the slope protection, and mark the paving height of the coarse sand filter material and the elevation of the masonry surface. Set a control point every 3 m on the vertical slope to facilitate paving. Fill with filter material and masonry. The coarse sand reverse filter material is laid manually from bottom to top and wetted with water. It is manually pounded with a shovel and leveled with wires. When masonry, select stones of about 40 cm from the stones, use the flatter side as the slope surface, and hammer the protruding parts with a hand hammer to improve the appearance. The flatness of the slope is controlled by measuring points and hanging wires. The stone masonry must be implemented in four directions: "smooth, stable, dense and staggered". The mortar used in the masonry process is mixed strictly in accordance with the construction mix ratio. After the masonry is completed, the joints should be cleaned, pointed and maintained in a timely manner.
5 Construction quality control
5.1 Pay attention to rolling compaction test control
In order to verify whether the compaction of soil materials in each material yard can meet the design indicators, according to the conditions at the construction site Some rolling equipment sets different filling thicknesses and different rolling passes to determine various compaction parameters required by the design. And check whether the performance of the compaction equipment meets the construction requirements. Before each material yard is used, a rolling test of the upper embankment soil materials is carried out. This project conducted 4 rolling compaction tests. The following conclusions were drawn through the tests: ① The rolling compaction machinery can meet the construction requirements. The vibration rolling speed is 2.0 km/h and the vibration frequency is 35 Hz. It not only meets the specification requirements, but also reaches The vibration effect required by the design. This can be done during construction. ②The thickness of the paving material passed the test is set at 50 cm. ③The number of rolling passes is set as 1→2→1. ④ When the natural moisture content of the material yard is between 4.5% and 7%, it meets the construction requirements and can be used directly during construction. If it is lower or higher than this standard, it should be sprayed with water or dried in the sun before being put on the embankment.
5.2 Control of basic treatment measures
Before embankment filling, remove turf, tree roots, humus and other debris on the ground at the proposed embankment location, and the depth of base removal should reach 30 cm. , the scope exceeds the design edge by 50 cm. During the actual construction process, no silt, water accumulation, etc. was found. If this phenomenon occurs, it must be reported to the supervisor in time and a replacement plan shall be proposed.
5.3 Quality control of the earth material yard
Before construction, the construction unit should estimate the soil materials in the earth material field to ensure that it meets the requirements for filling the embankment. The surface silt soil, impurity soil, expansive soil, scattered soil materials, turf, tree roots, etc. must be removed. The moisture content of the soil materials must also be controlled. When the moisture content of the soil materials is high, the soil can be dug out and turned over to dry. Transportation and filling will not be carried out until the moisture content of the soil material meets the requirements.
5.4 Quality control of embankment filling
After the embankment foundation is accepted, the embankment filling construction can be carried out. When filling soil materials, the filling thickness of each layer shall strictly follow the selection plan of the rolling compaction test, and shall be layered horizontally, and shall be filled layer by layer strictly starting from the lower part, with the edge line exceeding the designed edge line by 30 cm. The rolling machine also adopts the scheme adopted in the rolling test for rolling. The direction of travel of the rolling machine should be parallel to the axis of the embankment, and the rolling should be carried out in sections and in layers. Manual compaction should be used for parts that cannot be rolled by the machine. After the embankment is filled, slope cutting and shaping will be carried out. During this construction process, sufficient personnel must be assigned to direct the paving to ensure that the thickness of each layer of paving is uniform, no leakage occurs, and the filling quality is ensured.
5.5 Construction progress control measures
The arrangement of the construction progress plan determines whether the construction can be completed smoothly and with quality and quantity. For this project, the principle of construction schedule arrangement is to combine the natural conditions of the site and the logical relationship between the construction procedures and spatial layout of the unit project to ensure the balance and continuity of the project construction.
6 Conclusion
In short, the importance of the construction of flood control embankment projects to urban safety is self-evident. During the construction process, the requirements of the drawings must be strictly followed, problems encountered must be solved as soon as possible, construction quality control must be strengthened, and acceptance work must be strictly controlled so that the flood control embankment project can truly play its role and protect the safety of urban people's lives and property.
For more information about engineering/service/purchasing tender document writing and production to improve the bid winning rate, you can click on the official website customer service at the bottom for free consultation: /#/?source=bdzd