Urban spoil roadbed ash mixing improvement construction method

Abstract

The invention discloses an urban spoil roadbed ash mixing improvement construction method. Relates to the technical field of roadbed ash mixing construction. 2, roadbed ash mixing construction; 3, retaining, reinforcing and protecting the roadbed; and 4, roadbed and pavement drainage system construction. According to the method, the construction method for mixing the ash into the urban spoil roadbed is improved, so that the accuracy of the ash mixing amount and the mixing uniformity can be strictly controlled, the compaction quality detection is nondestructive and rapid, the technical problems that the roadbed is scientifically filled by using the urban spoil and the compaction quality detection is difficult are solved, and the engineering quality is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of roadbed lime-mixing construction, and more particularly to an improved construction method for urban abandoned soil roadbed lime-mixing. Background Art

[0002] In recent years, my country's urban construction has developed rapidly. Excavation of construction foundation pits and municipal subways has generated a large amount of urban waste. These urban wastes are mainly over-wet soil, some are weakly expansive soil, and there is a small amount of construction waste. The stacking of urban waste has a great impact on the environment and land resources. How to reasonably utilize urban waste is an urgent problem.

[0003] The highway subgrade is a linear structure, and the earthwork demand is large. If the urban spoil can be reasonably used for the filling of the highway subgrade, it will not only solve the problem of soil acquisition, but also help solve the problem of spoil stacking, which is in line with the "less excavation, zero waste" green highway construction concept. However, since most of the urban spoil is too wet soil, the project schedule is tight and it is difficult to dry it, and the source is not fixed, the performance varies greatly, and the compaction index is obviously not suitable for the quality control of subgrade compaction. The construction method, compaction index and quality control of the urban spoil subgrade are practical problems facing the urban spoil subgrade.

[0004] Therefore, how to provide a lime-mixed improved construction method for urban abandoned soil roadbed such as over-wet soil and weak expansive soil is an engineering problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a construction method for improving urban abandoned soil roadbed by mixing lime, aiming to solve one of the problems in the above-mentioned background technology, rationally utilize urban abandoned soil such as over-wet soil and weak expansive soil, ensure the quality of the project, and realize the resource utilization of urban abandoned soil.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A construction method for improving urban abandoned soil roadbed by mixing lime, comprising the following steps:

[0008] Step 1: Construction preparation

[0009] Construction measurement: Before construction, the roadbed construction measurement shall be carried out according to the current construction specifications;

[0010] Test: Take samples of urban abandoned soil such as over-wet soil and weak expansive soil to be used as roadbed filler, prepare improved soil according to the lime ratio of 2%, 4%, 6%, 8%, and 10%, and conduct compaction, CBR, and dynamic rebound modulus tests respectively. According to the requirements of CBR, roadbed top surface rebound modulus, and expansion rate ≤3% for each part of the roadbed, determine the applicable lime ratio of urban abandoned soil, the lime ratio of roadbed is 6%, and the lime ratio of embankment is 4%;

[0011] Surface treatment: Before embankment filling, the surface of the foundation shall be cleared. When the horizontal slope of the steep slope or ditch slope is steeper than 1:5, a step with a width of not less than 2.0m shall be excavated; measures shall be taken to intercept and drain the groundwater that affects the stability of the embankment, and materials with good water permeability shall be selected for filling; the foundation after surface cleaning shall be compacted by rolling, and the compaction degree shall not be less than 90%;

[0012] Test section: Select a representative section with geological conditions and roadbed section form, with a length of not less than 200m; pave the test road with loose paving thickness of 20cm, 25cm and 30cm respectively, and specify the mechanical combination of lime-added improved soil, compaction machinery specifications, loose paving thickness, number of rolling times, rolling speed, rolling moisture content, compaction, etc.; the mechanical combination is loader, transport vehicle, bulldozer, grader, roller (vibratory roller, static three-wheel roller), cold regeneration mixer, powder spreader, and sprinkler; the dead weight of the vibratory roller is not less than 26t, and the working weight of the static three-wheel roller is not less than 20t; the powder spreader has its own metering system, which is calibrated and calibrated regularly; the number of rolling times is not less than 6 times, the rolling speed is 2-4km / h, and the rolling moisture content is 1%-2% higher than the optimal moisture content;

[0013] 1) After the test section is finely leveled, it is divided into three rolling areas of equal length. The starting and ending lines, lane markings, etc. of the three rolling areas are marked by inserting poles, hanging lines, and spreading ash;

[0014] 2) Use vibratory rollers and static three-wheel rollers with a deadweight of 26t or more, and roll at a rolling speed of 2-4.0km / h, in accordance with three rolling conditions: static rolling 1 time + strong vibration 2 times + static rolling 1 time, static rolling 1 time + strong vibration 4 times + static rolling 1 time, static rolling 1 time + strong vibration 6 times + static rolling 1 time, until the entire rolling surface is rolled; before entering the starting line of the rolling area, the vibratory roller reaches a normal vibration state;

[0015] 3) After rolling is completed, select no less than 2 test sections in the three rolling areas, and select no less than 6 test points in each test section; each test point first tests the dynamic deformation modulus and then the compaction degree K;

[0016] 4) Since urban waste soil such as over-wet soil and weak expansive soil has a wide range of sources and large differences in particle composition, maximum dry density, etc., after the compaction K test of each test point is completed, sampling is carried out in accordance with the provisions of the compaction test of the Highway Geotechnical Test Code (JTG3430-2020) T0131-2019 to obtain the maximum dry density of the engineering waste soil at each test point, which is used as the calculation basis for the compaction of the test point to accurately obtain the compaction of the test point;

[0017] 5) According to the dynamic deformation modulus E measured on site vdand compaction degree K, establish the dynamic deformation modulus E vd The correlation coefficient between the compaction degree K is not less than 0.80;

[0018] 6) Dynamic deformation modulus E measured on site vd The correlation with the compaction degree K was determined using the following linear regression model;

[0019] y=a+bx

[0020] Among them, x is the compaction index; y is the dynamic deformation modulus index; a and b are regression parameters;

[0021] The control standard of dynamic deformation modulus adopts the linear regression model and regression parameters determined in 6) and is determined according to the control standard of compaction degree K; as shown in the following formula:

[0022] [E vd ]=a+b×[k]

[0023] Where [k] is the compaction control standard of compaction quality; [E vd ] is the dynamic deformation modulus control standard of compaction quality;

[0024] Step 2: Roadbed lime construction

[0025] Roadbed, treated thickness 80cm, improved by 6% ash addition;

[0026] Embankment, within the treatment thickness embankment range, 4% lime is added to improve;

[0027] Execute the construction process of "hanging lines and drawing grids to lay soil, rough paving, fine leveling with a grader, spreading with a powder spreader, mixing with a cold recycling mixer, final leveling, rolling and compacting, inspection, curing, and roadbed repair";

[0028] 1 Hanging line painting grid on the soil

[0029] According to the load of each car and the loose paving thickness, the size of the grid is calculated according to the principle of one car per grid, and the grid is made with lime and the material is added;

[0030] 2. Pave the rough surface

[0031] After a certain amount of soil is added, a bulldozer is used to spread and level the soil. The moisture content of the soil is tested. If the moisture content of the soil is 5% higher than the optimum moisture content, a plow is used to loosen and dry the soil, and then a bulldozer is used to roughly level the soil. The last layer of the roadbed is laid in accordance with the principle of "higher rather than lower" to avoid thin layer leveling.

[0032] 3. Grader fine leveling

[0033] After the bulldozer has paved the rough surface, it is then rolled with a three-wheel roller, then scraped with a grader, and rolled again with a three-wheel roller;

[0034] 4. Powder spreading vehicle

[0035] On the finely leveled working surface, a fully automatic powder spreading vehicle is used to spread lime, and the spreading situation is detected in real time; the spreading vehicle's speed and spreading amount parameters are strictly controlled; the spreading amount is controlled to be 0.5% higher than the design value;

[0036] 5 Cold recycling mixer mixing

[0037] After the powder spreading vehicle spreads the powder over a certain area, the cold recycling mixer starts mixing;

[0038] 1) Determine the number of mixing times according to the mixing uniformity, which should not be less than 2 times;

[0039] 2) The mixing depth into the underlying layer shall be no less than 10mm;

[0040] 3) The horizontal overlap width of mixing should be controlled between 30cm and 50cm, and the vertical overlap of mixing sections should not be less than 5m;

[0041] 4) Strictly control the running speed of the cold regeneration mixer according to the speed determined in the test section;

[0042] 5) During the mixing process, timely check the moisture content and ash dosage of the mixture; when the moisture content is low, use a sprinkler truck to add water by atomization, and the moisture content should be 1%-2% higher than the optimal moisture content; when the ash dosage is insufficient, add lime again; try not to use soil with too high a moisture content, and turn the mixture over and dry it in the construction section;

[0043] 6 Final draw

[0044] After mixing evenly, the final leveling is carried out by static pressing with a three-wheel roller, scraping with a grader, and static pressing with a three-wheel roller. The final leveling follows the principles of "from the roadside to the middle of the road, from the low side to the high side" and "scraping rather than patching", and the loose paving thickness is strictly controlled;

[0045] 7. Rolling and compaction

[0046] After the final leveling is completed, rolling shall be carried out as soon as possible; the rolling shall follow the principles of "light first, heavy later, slow first, fast later", "from the roadside to the middle of the road, from the low side to the high side", and longitudinal rolling shall be carried out wheel by wheel according to the compaction machinery and compaction times determined in the test section;

[0047] 1) Use three steel wheel rollers to press statically for the first time, use a vibratory roller to press 4-6 times, and then use three steel wheel rollers to press statically for the last time to form the product;

[0048] 2) The rolling speed is controlled at 2-4 km / h;

[0049] 3) Overlap the wheel tracks by 1 / 3 when rolling;

[0050] 4) Equipped with small compaction and tamping equipment to process corners, dead corners and other parts;

[0051] 5) The rolling shall be completed on the same day, and the longest time shall not exceed 4 days;

[0052] 6) It is prohibited to turn around or brake suddenly on the road section where the rolling equipment has been completed or is being rolled;

[0053] 7) If "spring", slurry overflow, looseness, peeling, etc. are found during rolling, they should be dealt with in time;

[0054] 8 Inspection

[0055] After rolling, the dynamic deformation modulus and ash dosage are tested; the dynamic deformation modulus is not lower than the control standard determined in the test section. The detection method adopts E vd Deformation modulus instrument; ash dosage detection adopts EDTA titration method, and the ash dosage control standard meets the following requirements: roadbed ≥6%, embankment ≥4%; the detection frequency is not less than 6 points per 200m per compaction layer; the compaction quality of weak areas such as edges, corners, and the junction of new and old parts is tested;

[0056] 1) Surface inspection: The surface is flat, without potholes, "springs", debris, obvious wheel marks, etc. The roadside line is straight, and the slope is smooth, stable, and has no defective slope;

[0057] 2) Measured items: elevation, center line, cross slope, width, flatness, dynamic deformation modulus and other indicators;

[0058] 9. Health

[0059] Urban abandoned soil improvement should be constructed continuously. After passing the inspection, if the upper layer can be constructed continuously, no special curing period is required; if the upper layer cannot be constructed continuously, it should be covered with geotextile and watered in time for curing; the curing period shall not be less than 7 days;

[0060] 1) Sprinklers and other methods are used for watering health care; pipe watering is prohibited;

[0061] 2) When the sprinkler truck is spraying water, it is prohibited to roll over the newly formed roadbed;

[0062] 3) Traffic will be closed during the maintenance period, and non-maintenance vehicles are prohibited from driving;

[0063] 10 Roadbed repair

[0064] After the roadbed is filled to the designed elevation, the roadbed is repaired; the roadbed repair meets the requirements of the current specifications;

[0065] Step 3: Roadbed protection

[0066] When the roadbed slope height H≤3.0m, the embankment slope is protected by a three-dimensional vegetation net with grass and shrubs;

[0067] When the roadbed slope height H>3.0m, the embankment slope is protected by arched slope protection, the arch frame is assembled with C30 concrete prefabricated blocks, and the arch foot is set with C25 cast-in-place concrete foot wall foundation;

[0068] Step 4: Roadbed and pavement drainage, including roadbed drainage and pavement drainage:

[0069] Roadbed drainage includes:

[0070] Embankment drainage ditch

[0071] A longitudinal drainage ditch is set outside the embankment slope. The C30 concrete prefabricated trapezoidal drainage ditch is used. The side walls and bottom of the drainage ditch are paved with 5cm cement mortar. A 10cm gravel cushion is pre-paved under the bottom cement mortar. The cross-sectional dimensions of the drainage ditch are 0.9m wide at the upper mouth and 0.6m wide at the lower mouth. The height of the drainage ditch is 0.6m. The 1.0m outside the side ditch is the land boundary. The distance between the outlets of the longitudinal drainage ditch should not exceed 300m. The outlet should be connected to natural ditches, rivers, ponds, or connected to natural ditches, rivers, ponds, or through culverts and transverse drainage ditches. The water in the drainage ditch is led out of the roadbed range and not directly discharged into nearby drinking and protected water bodies. If it cannot be avoided, purification facilities in purification pools should be added;

[0072] Road cutting ditch

[0073] A rectangular cover ditch is used, and the effective water-passing cross-sectional dimensions of the ditch are mainly 60x60cm and 60x120cm. The ditch body is cast in situ with C30 concrete, and the cover is prefabricated with C30 reinforced concrete. The longitudinal slope of the ditch bottom is consistent with the longitudinal slope of the route as much as possible, and is not less than 0.3%;

[0074] Road drainage includes:

[0075] Pavement surface drainage

[0076] The road surface drainage adopts a combination of centralized drainage and decentralized drainage. Hardened protrusions are set on the outer edge of the earth shoulder prefabricated block, and the road surface water flows horizontally to the edge of the earth shoulder, and then drains the collected water to the rapids trough through the outlets set at a certain distance longitudinally, and finally drains into the embankment drainage ditch;

[0077] Central median drainage

[0078] It consists of a waterproof layer, a longitudinal drainage ditch and a transverse drainage pipe; a φ100mm PVC perforated seepage pipe is set in the longitudinal gravel seepage ditch, and the rainwater in the middle zone is collected into the water collection trough through the perforated seepage pipe; the water collection trough is set below the top surface of the roadbed, in a rectangular shape, 0.5m wide and 0.25m deep; the water in the water collection trough is led out through the transverse drainage pipe, and the longitudinal and transverse drainage pipes are connected with C20 prefabricated blocks; the transverse drainage pipes are arranged alternately on the left and right sides, and the transverse drainage pipes are connected with the longitudinal drainage pipes. Seepage ditches are connected through water collection troughs. The longitudinal drainage seepage ditch is disconnected at bridges and open culverts. Transverse drainage pipes are added at the upstream of the water flow and at the bottom of the concave curve. The transverse drainage pipes are φ110mm PVC pipes with a wall thickness of 4.8mm. When the PVC pipes are laid, they extend 10cm beyond the roadbed slope. The longitudinal slope of the longitudinal drainage seepage ditch bottom is not less than 0.3%. Seepage-proof geotextiles are laid at the junction of the backfill soil and the pavement structure of the central dividing strip and the junction of the seepage ditch and the roadbed, and anti-filtration geotextiles are laid on the top surface of the seepage ditch.

[0079] Internal drainage of pavement structures

[0080] A lower sealing layer is set on the top surface of the pavement base to intercept water seepage from the pavement; in the fill section, the seepage water is drained through the cross slope of the road arch to the gravel cushion layer fully covered at the edge of the earth shoulder, and then drained to the slope through horizontal drainage; in the excavation section, the seepage water is drained through the cross slope of the road arch to the gravel cushion layer fully covered at the edge of the earth shoulder, and then drained to the side ditch of the road cut through the drainage holes, and finally discharged longitudinally through the side ditch of the road cut.

[0081] It can be seen from the above technical scheme that compared with the prior art, the present invention discloses an improved construction method for mixing ash with urban abandoned soil roadbed. By improving the construction method for mixing ash with urban abandoned soil roadbed, the accuracy of the ash mixing amount, the uniformity of mixing, and the non-destructive and rapid compaction quality detection can be strictly controlled, which solves the technical problems of scientifically utilizing urban abandoned soil to fill roadbed and the difficulty in compaction quality detection, and ensures the quality of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0083] Figure 1 The present invention provides a flow chart of the improved construction method for urban abandoned soil roadbed by mixing lime. DETAILED DESCRIPTION

[0084] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0085] See also Figure 1 The embodiment of the present invention discloses a construction method for improving urban abandoned soil roadbed by mixing lime, comprising the following steps:

[0086] Step 1: Construction preparation

[0087] Construction measurement: Before construction, the roadbed construction measurement shall be carried out according to the current construction specifications;

[0088] Test: Take samples of urban abandoned soil such as over-wet soil and weak expansive soil to be used as roadbed filler, prepare improved soil according to the lime ratio of 2%, 4%, 6%, 8%, and 10%, and conduct compaction, CBR, and dynamic rebound modulus tests respectively. According to the requirements of CBR, roadbed top surface rebound modulus, and expansion rate ≤3% for each part of the roadbed, determine the applicable lime ratio of urban abandoned soil, the lime ratio of roadbed is 6%, and the lime ratio of embankment is 4%;

[0089] Surface treatment: Before embankment filling, the surface of the foundation shall be cleared. When the horizontal slope of the steep slope or ditch slope is steeper than 1:5, a step with a width of not less than 2.0m shall be excavated; measures shall be taken to intercept and drain the groundwater that affects the stability of the embankment, and materials with good water permeability shall be selected for filling; the foundation after surface cleaning shall be compacted by rolling, and the compaction degree shall not be less than 90%;

[0090] Test section: Select a representative section with geological conditions and roadbed section form, with a length of not less than 200m; pave the test road with loose paving thickness of 20cm, 25cm and 30cm respectively, and specify the mechanical combination of lime-added improved soil, compaction machinery specifications, loose paving thickness, number of rolling times, rolling speed, rolling moisture content, compaction, etc.; the mechanical combination is loader, transport vehicle, bulldozer, grader, roller (vibratory roller, static three-wheel roller), cold regeneration mixer, powder spreader, and sprinkler; the dead weight of the vibratory roller is not less than 26t, and the working weight of the static three-wheel roller is not less than 20t; the powder spreader has its own metering system, which is calibrated and calibrated regularly; the number of rolling times is not less than 6 times, the rolling speed is 2-4km / h, and the rolling moisture content is 1%-2% higher than the optimal moisture content;

[0091] 1) After the test section is finely leveled, it is divided into three rolling areas of equal length. The starting and ending lines, lane markings, etc. of the three rolling areas are marked by inserting poles, hanging lines, and spreading ash;

[0092] 2) Use vibratory rollers and static three-wheel rollers with a deadweight of 26t or more, and roll at a rolling speed of 2-4.0km / h, in accordance with three rolling conditions: static rolling 1 time + strong vibration 2 times + static rolling 1 time, static rolling 1 time + strong vibration 4 times + static rolling 1 time, static rolling 1 time + strong vibration 6 times + static rolling 1 time, until the entire rolling surface is rolled; before entering the starting line of the rolling area, the vibratory roller reaches a normal vibration state;

[0093] 3) After rolling is completed, select no less than 2 test sections in the three rolling areas, and select no less than 6 test points in each test section; each test point first tests the dynamic deformation modulus and then the compaction degree K;

[0094] 4) Since urban waste soil such as over-wet soil and weak expansive soil has a wide range of sources and large differences in particle composition, maximum dry density, etc., after the compaction K test of each test point is completed, sampling is carried out in accordance with the provisions of the compaction test of the Highway Geotechnical Test Code (JTG3430-2020) T0131-2019 to obtain the maximum dry density of the engineering waste soil at each test point, which is used as the calculation basis for the compaction of the test point to accurately obtain the compaction of the test point;

[0095] 5) According to the dynamic deformation modulus E measured on site vd and compaction degree K, establish the dynamic deformation modulus E vd The correlation coefficient between the compaction degree K is not less than 0.80;

[0096] 6) Dynamic deformation modulus E measured on site vd The correlation with the compaction degree K was determined using the following linear regression model;

[0097] y=a+bx

[0098] Among them, x is the compaction index; y is the dynamic deformation modulus index; a and b are regression parameters;

[0099] The control standard of dynamic deformation modulus adopts the linear regression model and regression parameters determined in 6) and is determined according to the control standard of compaction degree K; as shown in the following formula:

[0100] [E vd ]=a+b×[k]

[0101] Where [k] is the compaction control standard of compaction quality; [E vd ] is the dynamic deformation modulus control standard of compaction quality;

[0102] Step 2: Roadbed lime construction

[0103] Roadbed, treated thickness 80cm, improved by 6% ash addition;

[0104] Embankment, within the treatment thickness embankment range, 4% lime is added to improve;

[0105] Execute the construction process of "hanging lines and drawing grids to lay soil, rough paving, fine leveling with a grader, spreading with a powder spreader, mixing with a cold recycling mixer, final leveling, rolling and compacting, inspection, curing, and roadbed repair";

[0106] 1 Hanging line painting grid on the soil

[0107] According to the load of each car and the loose paving thickness, the size of the grid is calculated according to the principle of one car per grid, and the grid is made with lime and the material is added;

[0108] 2. Pave the rough surface

[0109] After a certain amount of soil is added, a bulldozer is used to spread and level the soil. The moisture content of the soil is tested. If the moisture content of the soil is 5% higher than the optimum moisture content, a plow is used to loosen and dry the soil, and then a bulldozer is used to roughly level the soil. The last layer of the roadbed is laid in accordance with the principle of "higher rather than lower" to avoid thin layer leveling.

[0110] 3. Grader fine leveling

[0111] After the bulldozer has paved the rough surface, it is then rolled with a three-wheel roller, then scraped with a grader, and rolled again with a three-wheel roller;

[0112] 4. Powder spreading vehicle

[0113] On the finely leveled working surface, a fully automatic powder spreading vehicle is used to spread lime, and the spreading situation is detected in real time; the spreading vehicle's speed and spreading amount parameters are strictly controlled; the spreading amount is controlled to be 0.5% higher than the design value;

[0114] 5 Cold recycling mixer mixing

[0115] After the powder spreading vehicle spreads the powder over a certain area, the cold recycling mixer starts mixing;

[0116] 1) Determine the number of mixing times according to the mixing uniformity, which should not be less than 2 times;

[0117] 2) The mixing depth into the underlying layer shall be no less than 10mm;

[0118] 3) The horizontal overlap width of mixing should be controlled between 30cm and 50cm, and the vertical overlap of mixing sections should not be less than 5m;

[0119] 4) Strictly control the running speed of the cold regeneration mixer according to the speed determined in the test section;

[0120] 5) During the mixing process, timely check the moisture content and ash dosage of the mixture; when the moisture content is low, use a sprinkler truck to add water by atomization, and the moisture content should be 1%-2% higher than the optimal moisture content; when the ash dosage is insufficient, add lime again; try not to use soil with too high a moisture content, and turn the mixture over and dry it in the construction section;

[0121] 6 Final draw

[0122] After mixing evenly, the final leveling is carried out by static pressing with a three-wheel roller, scraping with a grader, and static pressing with a three-wheel roller. The final leveling follows the principles of "from the roadside to the middle of the road, from the low side to the high side" and "scraping rather than patching", and the loose paving thickness is strictly controlled;

[0123] 7. Rolling and compaction

[0124] After the final leveling is completed, rolling shall be carried out as soon as possible; the rolling shall follow the principles of "light first, heavy later, slow first, fast later", "from the roadside to the middle of the road, from the low side to the high side", and longitudinal rolling shall be carried out wheel by wheel according to the compaction machinery and compaction times determined in the test section;

[0125] 1) Use three steel wheel rollers to press statically for the first time, use a vibratory roller to press 4-6 times, and then use three steel wheel rollers to press statically for the last time to form the product;

[0126] 2) The rolling speed is controlled at 2-4 km / h;

[0127] 3) Overlap the wheel tracks by 1 / 3 when rolling;

[0128] 4) Equipped with small compaction and tamping equipment to process corners, dead corners and other parts;

[0129] 5) The rolling shall be completed on the same day, and the longest time shall not exceed 4 days;

[0130] 6) It is prohibited to turn around or brake suddenly on the road section where the rolling equipment has been completed or is being rolled;

[0131] 7) If "spring", slurry overflow, looseness, peeling, etc. are found during rolling, they should be dealt with in time;

[0132] 8 Inspection

[0133] After rolling, the dynamic deformation modulus and ash dosage are tested; the dynamic deformation modulus is not lower than the control standard determined in the test section. The detection method adopts E vd Deformation modulus instrument; ash dosage detection adopts EDTA titration method, and the ash dosage control standard meets the following requirements: roadbed ≥6%, embankment ≥4%; the detection frequency is not less than 6 points per 200m per compaction layer; the compaction quality of weak areas such as edges, corners, and the junction of new and old parts is tested;

[0134] 1) Surface inspection: The surface is flat, without potholes, "springs", debris, obvious wheel marks, etc. The roadside line is straight, and the slope is smooth, stable, and has no defective slope;

[0135] 2) Measured items: elevation, center line, cross slope, width, flatness, dynamic deformation modulus and other indicators;

[0136] 9. Health

[0137] Urban abandoned soil improvement should be constructed continuously. After passing the inspection, if the upper layer can be constructed continuously, no special curing period is required; if the upper layer cannot be constructed continuously, it should be covered with geotextile and watered in time for curing; the curing period shall not be less than 7 days;

[0138] 1) Sprinklers and other methods are used for watering health care; pipe watering is prohibited;

[0139] 2) When the sprinkler truck is spraying water, it is prohibited to roll over the newly formed roadbed;

[0140] 3) Traffic will be closed during the maintenance period, and non-maintenance vehicles are prohibited from driving;

[0141] 10 Roadbed repair

[0142] After the roadbed is filled to the designed elevation, the roadbed is repaired; the roadbed repair meets the requirements of the current specifications;

[0143] Step 3: Roadbed protection

[0144] When the roadbed slope height H≤3.0m, the embankment slope is protected by a three-dimensional vegetation net with grass and shrubs;

[0145] When the roadbed slope height H>3.0m, the embankment slope is protected by arched slope protection, the arch frame is assembled with C30 concrete prefabricated blocks, and the arch foot is set with C25 cast-in-place concrete foot wall foundation;

[0146] Step 4: Roadbed and pavement drainage, including roadbed drainage and pavement drainage:

[0147] Roadbed drainage includes:

[0148] Embankment drainage ditch

[0149] A longitudinal drainage ditch is set outside the embankment slope. The C30 concrete prefabricated trapezoidal drainage ditch is used. The side wall and bottom of the drainage ditch are paved with 5cm cement mortar. A 10cm gravel cushion is pre-paved under the bottom cement mortar. The cross-sectional dimensions of the drainage ditch are 0.9m wide at the upper mouth and 0.6m wide at the lower mouth. The height of the drainage ditch is 0.6m. The 1.0m outside the side ditch is the land boundary. The distance between the outlets of the longitudinal drainage ditch should not exceed 300m. The outlet should be connected to natural ditches, rivers, ponds, or connected to natural ditches, rivers, ponds, or through culverts and transverse drainage ditches. The water in the drainage ditch is led out of the roadbed range and not directly discharged into nearby drinking and protected water bodies. If it cannot be avoided, purification facilities in purification pools should be added;

[0150] Road cutting ditch

[0151] A rectangular cover ditch is used, and the effective water-passing cross-sectional dimensions of the ditch are mainly 60x60cm and 60x120cm. The ditch body is cast in situ with C30 concrete, and the cover is prefabricated with C30 reinforced concrete. The longitudinal slope of the ditch bottom is consistent with the longitudinal slope of the route as much as possible, and is not less than 0.3%;

[0152] Road drainage includes:

[0153] Pavement surface drainage

[0154] The road surface drainage adopts a combination of centralized drainage and decentralized drainage. Hardened protrusions are set on the outer edge of the earth shoulder prefabricated block, and the road surface water flows horizontally to the edge of the earth shoulder, and then drains the collected water to the rapids trough through the outlets set at a certain distance longitudinally, and finally drains into the embankment drainage ditch;

[0155] Central median drainage

[0156] It consists of a waterproof layer, a longitudinal drainage ditch and a transverse drainage pipe; a φ100mm PVC perforated seepage pipe is set in the longitudinal gravel seepage ditch, and the rainwater in the middle zone is collected into the water collection trough through the perforated seepage pipe; the water collection trough is set below the top surface of the roadbed, in a rectangular shape, 0.5m wide and 0.25m deep; the water in the water collection trough is led out through the transverse drainage pipe, and the longitudinal and transverse drainage pipes are connected with C20 prefabricated blocks; the transverse drainage pipes are arranged alternately on the left and right sides, and the transverse drainage pipes are connected with the longitudinal drainage pipes. Seepage ditches are connected through water collection troughs. The longitudinal drainage seepage ditch is disconnected at bridges and open culverts. Transverse drainage pipes are added at the upstream of the water flow and at the bottom of the concave curve. The transverse drainage pipes are φ110mm PVC pipes with a wall thickness of 4.8mm. When the PVC pipes are laid, they extend 10cm beyond the roadbed slope. The longitudinal slope of the longitudinal drainage seepage ditch bottom is not less than 0.3%. Seepage-proof geotextiles are laid at the junction of the backfill soil and the pavement structure of the central dividing strip and the junction of the seepage ditch and the roadbed, and anti-filtration geotextiles are laid on the top surface of the seepage ditch.

[0157] Internal drainage of pavement structures

[0158] A lower sealing layer is set on the top surface of the pavement base to intercept water seepage from the pavement; in the fill section, the seepage water is drained through the cross slope of the road arch to the gravel cushion layer fully covered at the edge of the earth shoulder, and then drained to the slope through horizontal drainage; in the excavation section, the seepage water is drained through the cross slope of the road arch to the gravel cushion layer fully covered at the edge of the earth shoulder, and then drained to the side ditch of the road cut through the drainage holes, and finally discharged longitudinally through the side ditch of the road cut.

[0159] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it is relative to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0160] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A construction method for improving urban abandoned soil roadbed by mixing lime, characterized in that: The following steps are involved: Step 1: Construction preparation Construction measurement: Before construction, the roadbed construction measurement shall be carried out according to the current construction specifications; Test: Take samples of urban abandoned soil such as over-wet soil and weak expansive soil to be used as roadbed filler, prepare improved soil according to the lime ratio of 2%, 4%, 6%, 8%, and 10%, and conduct compaction, CBR, and dynamic rebound modulus tests respectively. According to the requirements of CBR, roadbed top surface rebound modulus, and expansion rate ≤3% for each part of the roadbed, determine the applicable lime ratio of urban abandoned soil, the lime ratio of roadbed is 6%, and the lime ratio of embankment is 4%; Surface treatment: Before embankment filling, the surface of the foundation shall be cleared. When the horizontal slope of the steep slope or ditch slope is steeper than 1:5, a step with a width of not less than 2.0m shall be excavated; measures shall be taken to intercept and drain the groundwater that affects the stability of the embankment, and materials with good water permeability shall be selected for filling; the foundation after surface cleaning shall be compacted by rolling, and the compaction degree shall not be less than 90%; Test section: Select a representative section with geological conditions and roadbed section form, with a length of not less than 200m; pave the test road with loose paving thickness of 20cm, 25cm and 30cm respectively, and specify the mechanical combination of lime-added improved soil, compaction machinery specifications, loose paving thickness, number of rolling times, rolling speed, rolling moisture content, compaction, etc.; the mechanical combination is loader, transport vehicle, bulldozer, grader, roller (vibratory roller, static three-wheel roller), cold regeneration mixer, powder spreader, and sprinkler; the dead weight of the vibratory roller is not less than 26t, and the working weight of the static three-wheel roller is not less than 20t; the powder spreader has its own metering system, which is calibrated and calibrated regularly; the number of rolling times is not less than 6 times, the rolling speed is 2-4km / h, and the rolling moisture content is 1%-2% higher than the optimal moisture content; 1) After the test section is finely leveled, it is divided into three rolling areas of equal length. The starting and ending lines, lane markings, etc. of the three rolling areas are marked by inserting poles, hanging lines, and spreading ash; 2) Use vibratory rollers and static three-wheel rollers with a deadweight of 26t or more, and roll at a rolling speed of 2-4.0km / h, in accordance with three rolling conditions: static rolling 1 time + strong vibration 2 times + static rolling 1 time, static rolling 1 time + strong vibration 4 times + static rolling 1 time, static rolling 1 time + strong vibration 6 times + static rolling 1 time, until the entire rolling surface is rolled; before entering the starting line of the rolling area, the vibratory roller reaches a normal vibration state; 3) After rolling is completed, select no less than 2 test sections in the three rolling areas, and select no less than 6 test points in each test section; each test point first tests the dynamic deformation modulus and then the compaction degree K; 4) Since urban waste soil such as over-wet soil and weak expansive soil has a wide range of sources and large differences in particle composition, maximum dry density, etc., after the compaction K test of each test point is completed, sampling is carried out in accordance with the provisions of the compaction test of the Highway Geotechnical Test Code (JTG3430-2020) T0131-2019 to obtain the maximum dry density of the engineering waste soil at each test point, which is used as the calculation basis for the compaction of the test point to accurately obtain the compaction of the test point; 5) According to the dynamic deformation modulus E measured on site vd With the compaction degree K, the dynamic deformation modulus E is established vd The correlation coefficient between the compaction degree K is not less than 0.80; 6) Dynamic deformation modulus E measured on site vd The correlation with the compaction degree K was determined using the following linear regression model; y=a+bx Among them, x is the compaction index; y is the dynamic deformation modulus index; a and b are regression parameters; The control standard of dynamic deformation modulus adopts the linear regression model and regression parameters determined in 6) and is determined according to the control standard of compaction degree K; as shown in the following formula: [AND vd ]=a+b×[k] Where [k] is the compaction control standard of compaction quality; [E vd ] is the dynamic deformation modulus control standard of compaction quality; Step 2: Roadbed lime construction Roadbed, treated thickness 80cm, improved by 6% ash addition; Embankment, within the treatment thickness embankment range, 4% lime is added to improve; Execute the construction process of "hanging lines and drawing grids to lay soil, paving rough leveling, land grader fine leveling, powder spreader spreading, cold recycling mixer mixing, final leveling, rolling and compacting, inspection, curing, and roadbed repair"; 1 Hanging line painting grid on the soil According to the load of each car and the loose paving thickness, the size of the grid is calculated according to the principle of one car per grid, and the grid is made with lime and the material is added; 2. Pave the rough surface After a certain amount of soil is added, a bulldozer is used to spread and level the soil. The moisture content of the soil is tested. If the moisture content of the soil is 5% higher than the optimum moisture content, the soil is first loosened and aired with a plow, and then roughly leveled with a bulldozer. The last layer of the roadbed is laid in accordance with the principle of "higher rather than lower" to avoid thin layer leveling.

3. Grader fine leveling After the bulldozer has paved the rough surface, it is then rolled with a three-wheel roller, then scraped with a grader, and rolled again with a three-wheel roller; 4. Powder spreading vehicle On the finely leveled working surface, a fully automatic powder spreading vehicle is used to spread lime, and the spreading situation is detected in real time; the spreading vehicle's speed and spreading amount parameters are strictly controlled; the spreading amount is controlled to be 0.5% higher than the design value; 5 Cold recycling mixer mixing After the powder spreading vehicle spreads the powder over a certain area, the cold recycling mixer starts mixing; 1) Determine the number of mixing times according to the mixing uniformity, which should not be less than 2 times; 2) The mixing depth into the underlying layer shall be no less than 10mm; 3) The horizontal overlap width of mixing should be controlled between 30cm and 50cm, and the vertical overlap of mixing sections should not be less than 5m; 4) Strictly control the running speed of the cold regeneration mixer according to the speed determined in the test section; 5) During the mixing process, timely check the moisture content and ash dosage of the mixture; when the moisture content is low, use a sprinkler truck to add water by atomization, and the moisture content should be 1%-2% higher than the optimal moisture content; when the ash dosage is insufficient, add lime again; try not to use soil with too high a moisture content, and turn the mixture over and dry it in the construction section; 6 Final draw After mixing evenly, the final leveling is carried out by static pressing with a three-wheel roller, scraping with a grader, and static pressing with a three-wheel roller. The final leveling follows the principle of "from the roadside to the middle of the road, from the low side to the high side" and "scraping rather than patching", and the loose paving thickness is strictly controlled; 7. Rolling and compaction After the final leveling is completed, rolling shall be carried out as soon as possible; the rolling shall follow the principle of "light first then heavy, slow first then fast" and "from the roadside to the middle of the road, from the low side to the high side", and the longitudinal rolling shall be carried out wheel by wheel according to the compaction machinery and compaction times determined in the test section; 1) Use three steel wheel rollers to press statically for the first time, use a vibratory roller to press 4-6 times, and then use three steel wheel rollers to press statically for the last time to form the product; 2) The rolling speed is controlled at 2-4 km / h; 3) Overlap the wheel tracks by 1 / 3 when rolling; 4) Equipped with small compaction and tamping equipment to process corners, dead corners and other parts; 5) The rolling shall be completed on the same day, and the longest time shall not exceed 4 days; 6) It is prohibited to turn around or brake suddenly on the road section where the rolling equipment has been completed or is being rolled; 7) If "spring", slurry overflow, looseness, peeling, etc. are found during rolling, they should be dealt with in time; 8 Inspection After rolling, the dynamic deformation modulus and ash dosage are tested; the dynamic deformation modulus is not lower than the control standard determined in the test section. The detection method adopts E vd Deformation modulus instrument; ash dosage detection adopts EDTA titration method, and the ash dosage control standard meets the following requirements: roadbed ≥6%, embankment ≥4%; the detection frequency is not less than 6 points per 200m per compaction layer; the compaction quality of weak areas such as edges, corners, and the junction of new and old parts is tested; 1) Surface inspection: The surface is flat, without potholes, "springs", debris, obvious wheel marks, etc. The roadside line is straight, and the slope is smooth, stable, and has no defective slope; 2) Measured items: elevation, center line, cross slope, width, flatness, dynamic deformation modulus and other indicators; 9. Health Urban abandoned soil improvement should be constructed continuously. After passing the inspection, if the upper layer can be constructed continuously, no special curing period is required; if the upper layer cannot be constructed continuously, it should be covered with geotextile and watered in time for curing; the curing period shall not be less than 7 days; 1) Sprinklers and other methods are used for watering health care; pipe watering is prohibited; 2) When the sprinkler truck is spraying water, it is prohibited to roll over the newly formed roadbed; 3) Traffic will be closed during the maintenance period, and non-maintenance vehicles are prohibited from driving; 10 Roadbed repair After the roadbed is filled to the designed elevation, the roadbed is repaired; the roadbed repair meets the requirements of the current specifications; Step 3: Roadbed protection When the roadbed slope height H≤3.0m, the embankment slope is protected by a three-dimensional vegetation net with grass and shrubs; When the roadbed slope height H>3.0m, the embankment slope is protected by arched slope protection, the arch frame is assembled with C30 concrete prefabricated blocks, and the arch foot is set with C25 cast-in-place concrete foot wall foundation; Step 4: Roadbed and pavement drainage, including roadbed drainage and pavement drainage: Roadbed drainage includes: Embankment drainage ditch A longitudinal drainage ditch is set outside the embankment slope. The C30 concrete prefabricated trapezoidal drainage ditch is used. The side wall and bottom of the drainage ditch are paved with 5cm cement mortar. A 10cm gravel cushion is pre-paved under the bottom cement mortar. The cross-sectional dimensions of the drainage ditch are 0.9m wide at the upper mouth and 0.6m wide at the lower mouth. The height of the drainage ditch is 0.6m. The 1.0m outside the side ditch is the land boundary. The distance between the outlets of the longitudinal drainage ditch should not exceed 300m. The outlet should be connected to natural ditches, rivers, ponds, or connected to natural ditches, rivers, ponds, or through culverts and transverse drainage ditches. The water in the drainage ditch is led out of the roadbed range and not directly discharged into nearby drinking and protected water bodies. If it cannot be avoided, purification facilities in purification pools should be added; Road cutting ditch A rectangular cover ditch is used, and the effective water-passing cross-sectional dimensions of the ditch are mainly 60x60cm and 60x120cm. The ditch body is cast in situ with C30 concrete, and the cover is prefabricated with C30 reinforced concrete. The longitudinal slope of the ditch bottom is consistent with the longitudinal slope of the route as much as possible, and is not less than 0.3%; Road drainage includes: Pavement surface drainage The road surface drainage adopts a combination of centralized drainage and decentralized drainage. Hardened protrusions are set on the outer edge of the earth shoulder prefabricated block, and the road surface water flows horizontally to the edge of the earth shoulder, and then drains the collected water to the rapids trough through the outlets set at a certain distance longitudinally, and finally drains into the embankment drainage ditch; Central median drainage It consists of a waterproof layer, a longitudinal drainage ditch and a transverse drainage pipe; a φ100mm PVC perforated seepage pipe is set in the longitudinal gravel seepage ditch, and the rainwater in the middle zone is collected into the water collection trough through the perforated seepage pipe; the water collection trough is set below the top surface of the roadbed, in a rectangular shape, 0.5m wide and 0.25m deep; the water in the water collection trough is led out through the transverse drainage pipe, and the longitudinal and transverse drainage pipes are connected with C20 prefabricated blocks; the transverse drainage pipes are arranged alternately on the left and right sides, and the transverse drainage pipes are connected with the longitudinal drainage pipes. Seepage ditches are connected through water collection troughs. The longitudinal drainage seepage ditch is disconnected at bridges and open culverts. Transverse drainage pipes are added at the upstream of the water flow and at the bottom of the concave curve. The transverse drainage pipes are φ110mm PVC pipes with a wall thickness of 4.8mm. When the PVC pipes are laid, they extend 10cm beyond the roadbed slope. The longitudinal slope of the longitudinal drainage seepage ditch bottom is not less than 0.3%. Seepage-proof geotextiles are laid at the junction of the backfill soil and the pavement structure of the central dividing strip and the junction of the seepage ditch and the roadbed, and anti-filtration geotextiles are laid on the top surface of the seepage ditch. Internal drainage of pavement structures A lower sealing layer is set on the top surface of the pavement base to intercept water seepage from the pavement; in the fill section, the seepage water is drained through the cross slope of the road arch to the gravel cushion layer fully covered at the edge of the earth shoulder, and then drained to the slope through horizontal drainage; in the excavation section, the seepage water is drained through the cross slope of the road arch to the gravel cushion layer fully covered at the edge of the earth shoulder, and then drained to the side ditch of the road cut through the drainage holes, and finally discharged longitudinally through the side ditch of the road cut.

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