Highway engineering base layer 3D intelligent paving construction method

Abstract

The invention relates to the technical field of highway engineering base course paving construction, in particular to a highway engineering base course 3D intelligent paving construction method which comprises the following steps: early-stage data preparation including original design data; making design data; layout of control points and benchmarks; instrument erection; importing design data; automatic paving is performed; performing rolling; and detecting the compaction degree, curing, and checking and accepting. The construction method has the beneficial effects that the positioning precision is high, differential positioning is adopted, the precision can reach the plane centimeter level and the elevation millimeter level, a large amount of manpower, material resources, financial resources and time are saved through digital, pile-free, intelligent, precise and trajectory construction, and the construction efficiency is improved. The influence of human factors on construction and generated errors are reduced to the maximum extent, and the working efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of highway engineering base paving construction, and in particular to a highway engineering base 3D intelligent paving construction method. Background Art

[0002] The inorganic binder structure layer of expressways and first-class highways is generally paved by hanging steel wire ropes to guide the elevation. During the paving process, the weight of the steel wire rope sags and the influence of human factors in leveling and laying out the lines can easily cause inaccurate elevation, resulting in uneven thickness of the inorganic binder structure layer, large ups and downs of the road surface, poor flatness, low driving comfort and other problems. Therefore, when paving the inorganic binder structure layer, how to reduce the influence of human factors in measuring and laying out and automatic leveling and paving by the paver, and effectively improve the flatness of the subbase and base layer, has become one of the key issues in controlling the flatness of road construction and improving driving comfort. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a 3D intelligent paving construction method for the base layer of a highway engineering project. The method of using GPS positioning and laser-guided elevation effectively solves the problems of uneven thickness of the structural layer and large fluctuations in flatness that are prone to occur in the traditional method during elevation surveying and automatic leveling and paving by the paver, reduces the influence of human factors on the flatness of the road surface, improves work efficiency, improves the flatness of the cement-stabilized gravel subbase and base layer, and improves the driving comfort of the entire road surface structure.

[0004] In order to achieve the above purpose, the technical solutions provided are as follows:

[0005] A 3D intelligent paving construction method for a highway engineering base layer, characterized by comprising the following steps:

[0006] Step 1: Preliminary data preparation; the original design data consists of 4 parts:

[0007] (1) Line, curve and corner table: The main input elements are the starting point coordinates, stake number, intersection point coordinates, stake number and curve element value;

[0008] (2) Longitudinal slope and vertical curve table: The main input elements are the starting point elevation, pile number and vertical curve elements;

[0009] (3) Roadbed design table: The main input elements are mileage pile number, roadbed width, and roadbed cross slope;

[0010] (4) Stake-by-stake coordinate table: Use the stake-by-stake coordinates to check whether the input road is correct:

[0011] (5) Design and construction data statistics: According to the design drawings and actual conditions, the pile numbers of different auxiliary structures are counted and organized in a unified manner to prepare for the production of design data;

[0012] Step 2: Design data production: Edit the road horizontal curve, vertical curve, cross slope and width in Topcon 3D-Office software according to the original design data, including the following steps:

[0013] (1) Load 3Doffice to create a new project and a new road project;

[0014] (2) After the new road project is completed, click Road Project (Alignment) / click Horizontal Center Line to open the input interface, and enter data in the element method format according to the straight line, curve and angle table;

[0015] (3) After the horizontal profile is completed, click Vertical Profile to open the input interface and enter the data in a certain format according to the longitudinal slope vertical curve table;

[0016] (4) After the vertical alignment is completed, click on the cross slope model (Templates) and input the cross slope model of the normal section and the super-elevated section according to the roadbed design table;

[0017] (5) After adding the cross slope model, click OK, then add the start and end pile numbers and the corresponding cross slope, left width, and right width to be constructed, and click OK;

[0018] (6) After adding the cross slope data, click the Generate TIN from 3Dalignment option, enter the grid spacing (the recommended value for straight sections is 1.5m, and the recommended value for superelevated sections is 0.2m), and click OK to generate the surface data;

[0019] (7) Calculate the height difference according to different positions and slopes, check whether the data is correct, and save the data for future use;

[0020] (8) When inputting cross slope data, all mileages of cross slope changes must be input without omission, wrong input or skipping;

[0021] (9) When making design data, the input structure layer width should be 1m wider than the maximum design width on both sides to prevent the automatic paving system from being unable to obtain surface data information and ensure that the paving does not exceed the designed surface width;

[0022] (10) When making surface data for normal sections (sections with unchanged cross slope of the roadbed), the grid spacing should be set to 1.5m when forming network data; if the spacing is too small, the data will be too large, which will cause it to not work properly when imported into the rover and GX-60;

[0023] (11) When preparing surface data for a slope-changing section (a section where the cross slope changes or a super-elevated section), in order to ensure the continuity of the screed plate when changing slopes during paving, the grid spacing should be 0.1 to 0.2 m, and the length of each section should not exceed 300 m. When the length of the surface data to be prepared exceeds 1000 m, it is advisable to prepare it in sections and switch the data during paving.

[0024] (12) The produced design data should be classified and stored, clearly marked to facilitate searching and modification;

[0025] Step 3: Control point and leveling point layout; including the following steps:

[0026] (1) Site inspection in the construction area: select a flat, hard, and unobstructed location around the construction site to set up control points and leveling points;

[0027] (2) Layout of field control points and leveling points: Figure 2 As shown in the figure, after the site survey is completed, the positions of the control points and leveling points are determined and laid out; the requirements for the layout of the control points and leveling points are as follows:

[0028] ① The control points should be arranged in a grid pattern in the construction area and cover the entire construction area;

[0029] ② The layout of control points should take into account the establishment of GPS base stations. The control points should cover the construction area and be no more than 500 meters away from the construction area;

[0030] ③ When laying out control points, keep them away from high-voltage lines, houses, rivers, gullies, etc. to prevent them from affecting the GPS base station’s reception of satellite signals;

[0031] ④ When laying out the leveling points, the laser station should be set up during paving to ensure that the laser information emitted by the laser station can be received by the MC-R3 receiver on the paver;

[0032] ⑤ The leveling points are usually laid out on both sides of the construction road. Since the laser emission range is within ±5m of the horizontal plane where the transmitter is located, and considering the influence of the longitudinal slope of the road, the leveling point is generally 1 to 2m higher than the top surface of the roadbed;

[0033] ⑥ To ensure the continuous and uninterrupted progress of the construction, two laser elevation reference stations need to be set up alternately. To ensure the elevation accuracy, the spacing between the leveling points is controlled at about 100m;

[0034] ⑦ When laying out the leveling points, choose a flat, hard, unobstructed location, more than 20 meters away from the construction section (excessive mechanical vibration during road construction will cause the laser station to shut down);

[0035] ⑧ When arranging control points and leveling points, choose a hard, flat, unobstructed location. The distance between control points should be between 300 and 500 meters, and the distance between leveling points should be about 100 meters. A temporary leveling point should be added between the leveling points to calibrate the height of the laser station instrument, with a temporary leveling point set every 50 meters;

[0036] ⑨ Control points and leveling points should be arranged in places that are not easily disturbed and reinforced with concrete. After the arrangement is completed, the control points and leveling points are as follows: Figure 2 As shown;

[0037] (3) Control point and leveling point surveying and setting: The control points shall be surveyed and set according to the first-class traverse accuracy requirements, and the leveling points shall be surveyed and set according to the fourth-class leveling requirements;

[0038] Step 4: Instrument setup, including the following steps:

[0039] (1) Installation of GPS base station

[0040] ① Before paving, select the control point closest to the construction section to set up a millimeter GPS reference station;

[0041] ②Align the leveling instrument and measure the height of the instrument;

[0042] ③ Turn on the base station, wait for the normal working prompt voice to sound, connect to the mobile station hand via Bluetooth, and set the base station's point number, instrument height, radio channel and other parameters;

[0043] ④Observe the battery power, satellite reception and radio signal transmission of the base station. After all indicators are working normally, connect the mobile station receiver to see if it can work normally.

[0044] ⑤ Lay out other known control points, and control the plane position error within ±2cm. This is used to check whether the GPS base station is set up correctly;

[0045] (2) Installation of PZL-1 laser elevation reference station

[0046] ① Before starting construction, determine the location of the first laser station, and select a leveling point 20-30m away from the side and rear of the paver as the first laser station. If the first laser station is set up too far away, it is easy to cause inaccurate elevation information. If it is set up on the side or front of the paver, the laser elevation information is easily blocked, which may cause the automatic paving system to fail to work properly;

[0047] ②After determining the location of the leveling point, set up the laser reference station on the tripod. First, automatically level the instrument and accurately center the leveling point;

[0048] ③Measure the installation height of the laser station instrument (from the leveling point to the marking on the side of the instrument);

[0049] ④Connect the hand to the laser station through Bluetooth, and set various parameters such as instrument height, model, station location, laser transmission channel, etc.

[0050] ⑤ Connect the mobile station to a position 5m away from the laser station, align the mobile station laser receiver with the laser station, and check whether the laser station is working properly;

[0051] ⑥ After the laser station is working properly, place the mobile station at the nearest leveling point, and stake out the three-dimensional coordinates of the leveling point so that the elevation error does not exceed 3mm. If it exceeds the error range, it needs to be calibrated again;

[0052] ⑦ When calibrating the laser station, the level point of the laser station should be 40-80m away from the level point where the laser station is set up. The laser station instrument height calibration shall not be carried out within 20m of the laser station.

[0053] ⑧ When the instrument is set up and the laser station instrument is calibrated, confirm whether the rover height is entered correctly. After the laser station height calibration is completed, select another 2 to 3 leveling points to check whether the height is correct;

[0054] ⑨After the GPS base station and laser elevation base station are set up, use the mobile station to stake out 2-3 control points and leveling points, check the three-dimensional coordinates, and confirm that all instruments are working properly and all data are accurate;

[0055] Step 5: Import design data, including the following steps:

[0056] (1) Importing design and construction data into the millimeter GPS mobile station: Import the prepared paving surface data (.TN3 format) and road data (.RD3 format) into the mobile station hand, and load the design data into the hand;

[0057] (2) On-site original ground verification: After the data is loaded, several cross sections are staked out to measure whether the surface data is correct and confirm whether the loose paving thickness is the designed loose paving thickness, so as to verify the accuracy of the elevation, transverse slope, longitudinal slope and other data of the designed data;

[0058] (3) Importing construction data into the paver control system: After the data is confirmed to be correct, export the surface data, control points, leveling points and other data and copy them to a USB flash drive (generally, the construction date of the day is used as the project file name); before the paver starts working, connect the GX-60 control box power supply, turn on the power and copy the project file exported from the hand to the software root directory; open the 3DMC software, select the project data according to the file name date, and load it;

[0059] Step 6: Automatic paving, specifically including the following steps:

[0060] (1) After the equipment is set up and calibrated, all data are imported into the mobile station and GX-60 control box. After all preparations are completed, paving operations can be carried out;

[0061] (2) Using the mobile station, the construction road to be paved is marked out based on the designed width and offset, and the formwork is supported;

[0062] (3) Before the paver is in place, use the mobile station to measure and place the screed pads so that the screed is on the designed loose paving surface when the paver is in place, and adjust the left and right scale readings of the paver;

[0063] (4) When the paver is ready, instruct the material truck to dump and spread the material, and start the paver. Turn off the automatic mode first, and walk 2m to 3m to measure with the mobile station to see whether the paved loose surface coincides with the designed surface. If there is a deviation, manually raise and lower the scales on both sides to make the elevation and cross slope of the paving surface reach the designed value;

[0064] (5) When the elevation, cross slope and other parameters are close to the design values, turn on the automatic switch to perform automatic leveling and paving;

[0065] (6) As the paver moves, the distance from the laser station at the starting position continues to increase. When the distance reaches about 100m, the laser receiving channels of the mobile station and the automatic paving system of the paver are changed to the laser station closer to the working area of ​​the paver;

[0066] (7) The laser stations are alternately set up in the paving direction to carry out continuous and uninterrupted paving operations;

[0067] (8) Use the mobile station to measure in real time whether the paving surface is consistent with the design, and make timely adjustments when fluctuations occur;

[0068] (9) When it is necessary to determine the loose paving coefficient, collect the elevation of the original ground points in advance. After the paving is completed and before rolling, measure the loose paving elevation. After rolling, measure the elevation after compaction. After the paving and rolling are completed, export the measured data.

[0069] (10) During the paving process, always pay attention to the automatic paving system receiving laser elevation information. If there is an interruption or no signal, turn off the automatic switch in time and pay attention to whether the paver scale fluctuates. Turn on the automatic switch after there is a signal.

[0070] (11) When the automatic paving control system on the paver selects the laser elevation information, the receivers on the left and right sides must select the laser signal emitted by the same laser reference station and must not receive laser signals from two instruments at the same time;

[0071] (12) When the paver is paving, the connected laser reference station should not be located on the road section being rolled. When the roller vibrates, the laser elevation information emitted by the laser reference station will fluctuate. Therefore, the laser elevation signal emitted by the laser reference station far away from the rolling section should be selected;

[0072] (13) When the paver is moving forward, the laser reference station should be set up alternately in the forward direction. After each setting, the instrument height should be calibrated. After the calibration is completed, the instrument height and point number should be recorded, and the corresponding data should be modified in the GX-60 control box;

[0073] (14) When adjusting the scale of the paver, it should be raised or lowered slowly and evenly, and should not be raised or lowered suddenly to prevent the formation of potholes that affect the flatness of the paving surface;

[0074] (15) After the construction is completed, the coordinate information and elevation information measured during the construction process are exported to facilitate the summary and analysis of the problems encountered during the construction process;

[0075] Step 7: rolling; the rolling scheme is as follows:

[0076] (1) The road section rolling scheme where the roller can start vibration

[0077] Initial rolling: Use 13t double steel wheels with full width static rolling once, with a rolling speed of 1.5-1.7km / h;

[0078] Recompaction: ① 22t single steel wheel static pressing once, vibration rolling twice, rolling speed 2-2.5km / h;

[0079] ② 26t single steel wheel vibrating rolling once, static rolling once, rolling speed 2-2.5km / h;

[0080] Final rolling: 30t tire roller rolling the full width twice, rolling speed 2-2.5km / h;

[0081] (2) Rolling plan for sections where the roller cannot start vibration

[0082] Initial rolling: Use 13t double steel wheels with full width static rolling once, with a rolling speed of 1.5-1.7km / h;

[0083] Re-pressing: ①22t single steel wheel static pressing 2 times, rolling speed 2-2.5km / h;

[0084] ②26t single steel wheel static pressing 2 times, rolling speed 2-2.5km / h;

[0085] ③36t single steel wheel static pressure 2 times, rolling speed 2-2.5km / h;

[0086] Final rolling: 30t tire roller rolling the full width twice, rolling speed 2-2.5km / h;

[0087] Step 8: Testing compaction, curing, and acceptance; specifically includes the following steps:

[0088] (1) The compaction degree requirement for the cement-stabilized crushed stone subbase of expressways is 97%, and the compaction degree requirement for the base layer is 98%. The sections that have been rolled should be inspected in a timely manner, and those that fail to meet the requirements should be re-compacted in a timely manner until the compaction degree meets the requirements;

[0089] (2) For sections that have been rolled and have passed the compaction test, the sections are covered with permeable geotextiles and watered for curing, and traffic is closed for curing for more than 7 days. The geotextiles are then uncovered 2 days before the next construction process.

[0090] (3) For road sections that have completed maintenance, each sub-item shall be inspected and accepted in accordance with the Highway Engineering Quality Inspection and Assessment Standards.

[0091] The principle of the present invention is as follows: the 3D digital road automatic paving control system is mainly composed of four parts: GPS reference station, PZL-1 laser elevation reference station, GPS mobile station and P63 paver automatic control system. When the system is working, the GPS reference station set up on the control point obtains the plane coordinate position information of the paving area, the PZL-1 laser reference station set up on the known leveling point transmits the elevation information, and the position information after the difference of the GPS base station and the elevation information transmitted by the laser station are transmitted to the MC-R3 receiver through the wireless data transmission station and the cable. After MC-R3 processes the received data, it transmits the three-dimensional coordinate data of the position of the ironing plate to the GX-60 control box in real time. The control box compares the current three-dimensional coordinate information obtained with the paving surface design data to generate corresponding elevation correction information. The control box then generates corresponding proportional drive signals corresponding to these information, and drives the hydraulic cylinder of the paver traction arm through the hydraulic valve to adjust the ironing plate in the corresponding direction, so that the paving surface produces slope and elevation changes, compensates for road surface fluctuations, and achieves the road surface flatness and thickness required by the design.

[0092] The beneficial effects of the present invention are:

[0093] 1. The construction method of the present invention has high positioning accuracy. By adopting differential positioning, the accuracy can reach centimeter level in plane and millimeter level in elevation.

[0094] 2. The construction method of the present invention saves a lot of manpower, material resources, financial resources and time through digital, pile-free, intelligent, precise and tracked construction, minimizes the impact of human factors on construction and the errors caused, and improves work efficiency.

[0095] Instruction Manual

[0096] Figure 1 It is a construction process flow chart of the present invention;

[0097] Figure 2 This is a schematic diagram of the layout of control points and leveling points in the present invention. DETAILED DESCRIPTION

[0098] 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.

[0099] Example 1

[0100] A 3D intelligent paving construction method for a highway engineering base layer, characterized by comprising the following steps:

[0101] Step 1: Preliminary data preparation; the original design data consists of 4 parts:

[0102] (1) Line, curve and corner table: The main input elements are the starting point coordinates, stake number, intersection point coordinates, stake number and curve element value;

[0103] (2) Longitudinal slope and vertical curve table: The main input elements are the starting point elevation, pile number and vertical curve elements;

[0104] (3) Roadbed design table: The main input elements are mileage pile number, roadbed width, and roadbed cross slope;

[0105] (4) Stake-by-stake coordinate table: Use the stake-by-stake coordinates to check whether the input road is correct:

[0106] (5) Design and construction data statistics: According to the design drawings and actual conditions, the pile numbers of different auxiliary structures are counted and organized in a unified manner to prepare for the production of design data;

[0107] Step 2: Design data production: Edit the horizontal curve, vertical curve, cross slope and width of the road in Topcon 3D-Office software according to the original design data, including the following steps:

[0108] (1) Load 3Doffice to create a new project and a new road project;

[0109] (2) After the new road project is completed, click Road Project (Alignment) / click Horizontal Center Line to open the input interface, and enter data in the element method format according to the line curve and angle table;

[0110] (3) After the horizontal profile is completed, click Vertical Profile to open the input interface and enter the data in a certain format according to the longitudinal slope vertical curve table;

[0111] (4) After the vertical alignment is completed, click on the cross slope model (Templates) and enter the cross slope model of the normal section and the super-elevated section according to the roadbed design table;

[0112] (5) After adding the cross slope model, click OK, then add the start and end pile numbers and the corresponding cross slope, left width, and right width to be constructed, and click OK;

[0113] (6) After adding the cross slope data, click the Generate TIN from 3Dalignment option, enter the grid spacing (the recommended value for straight sections is 1.5m, and the recommended value for superelevated sections is 0.2m), and click OK to generate the surface data;

[0114] (7) Calculate the height difference according to different positions and slopes, check whether the data is correct, and save the data for future use;

[0115] (8) When inputting cross slope data, all mileages of cross slope changes must be input without omission, wrong input or skipping;

[0116] (9) When making design data, the input structure layer width should be 1m wider than the maximum design width on both sides to prevent the automatic paving system from being unable to obtain surface data information and ensure that the paving does not exceed the designed surface width;

[0117] (10) When making surface data for normal sections (sections with unchanged cross slope of the roadbed), the grid spacing should be set to 1.5m when forming network data; if the spacing is too small, the data will be too large, which will cause it to not work properly when imported into the rover and GX-60;

[0118] (11) When preparing surface data for a slope-changing section (a section where the cross slope changes or a super-elevated section), in order to ensure the continuity of the screed plate when changing slopes during paving, the grid spacing should be 0.1 to 0.2 m, and the length of each section should not exceed 300 m. When the length of the surface data to be prepared exceeds 1000 m, it is advisable to prepare it in sections and switch the data during paving.

[0119] (12) The produced design data should be classified and stored, clearly marked to facilitate searching and modification;

[0120] Step 3: Control point and leveling point layout; including the following steps:

[0121] (1) Site inspection in the construction area: select a flat, hard, and unobstructed location around the construction site to set up control points and leveling points;

[0122] (2) Layout of field control points and leveling points: Figure 2 As shown in the figure, after the site survey is completed, the positions of the control points and leveling points are determined and laid out; the requirements for the layout of the control points and leveling points are as follows:

[0123] ① The control points should be arranged in a grid pattern in the construction area and cover the entire construction area;

[0124] ② The layout of control points should take into account the establishment of GPS base stations. The control points should cover the construction area and be no more than 500 meters away from the construction area;

[0125] ③ When laying out control points, keep them away from high-voltage lines, houses, rivers, gullies, etc. to prevent them from affecting the GPS base station’s reception of satellite signals;

[0126] ④ When laying out the leveling points, the laser station should be set up during paving to ensure that the laser information emitted by the laser station can be received by the MC-R3 receiver on the paver;

[0127] ⑤ The leveling points are usually laid out on both sides of the construction road. Since the laser emission range is within ±5m of the horizontal plane where the transmitter is located, and considering the influence of the longitudinal slope of the road, the leveling point is generally 1 to 2m higher than the top surface of the roadbed;

[0128] ⑥ To ensure the continuous and uninterrupted progress of the construction, two laser elevation reference stations need to be set up alternately. To ensure the elevation accuracy, the spacing between the leveling points is controlled at about 100m;

[0129] ⑦ When laying out the leveling points, choose a flat, hard, unobstructed location, more than 20 meters away from the construction section (excessive mechanical vibration during road construction will cause the laser station to shut down);

[0130] ⑧ When arranging control points and leveling points, choose a hard, flat, unobstructed location. The distance between control points should be between 300 and 500 meters, and the distance between leveling points should be about 100 meters. A temporary leveling point should be added between the leveling points to calibrate the height of the laser station instrument, with a temporary leveling point set every 50 meters;

[0131] ⑨ Control points and leveling points should be arranged in places that are not easily disturbed and reinforced with concrete. After the arrangement is completed, the control points and leveling points are as follows: Figure 2 As shown;

[0132] (3) Control point and leveling point surveying and setting: The control points shall be surveyed and set according to the first-class traverse accuracy requirements, and the leveling points shall be surveyed and set according to the fourth-class leveling requirements;

[0133] Step 4: Instrument setup, including the following steps:

[0134] (1) Installation of GPS base station

[0135] ① Before paving, select the control point closest to the construction section to set up a millimeter GPS reference station;

[0136] ②Align the leveling instrument and measure the height of the instrument;

[0137] ③ Turn on the base station, wait for the normal working prompt voice to sound, connect to the mobile station hand via Bluetooth, and set the base station's point number, instrument height, radio channel and other parameters;

[0138] ④Observe the battery power, satellite reception and radio signal transmission of the base station. After all indicators are working normally, connect the mobile station receiver to see if it can work normally.

[0139] ⑤ Lay out other known control points, and control the plane position error within ±2cm. This is used to check whether the GPS base station is set up correctly;

[0140] (2) Installation of PZL-1 laser elevation reference station

[0141] ① Before starting construction, determine the location of the first laser station, and select a leveling point 20-30m away from the side and rear of the paver as the first laser station. If the first laser station is set up too far away, it is easy to cause inaccurate elevation information. If it is set up on the side or front of the paver, the laser elevation information is easily blocked, which may cause the automatic paving system to fail to work properly;

[0142] ②After determining the location of the leveling point, set up the laser reference station on the tripod. First, automatically level the instrument and accurately center the leveling point;

[0143] ③Measure the installation height of the laser station instrument (from the leveling point to the marking on the side of the instrument);

[0144] ④Connect the hand to the laser station through Bluetooth, and set various parameters such as instrument height, model, station location, laser transmission channel, etc.

[0145] ⑤ Connect the mobile station to a position 5m away from the laser station, align the mobile station laser receiver with the laser station, and check whether the laser station is working properly;

[0146] ⑥ After the laser station is working properly, place the mobile station at the nearest leveling point, and stake out the three-dimensional coordinates of the leveling point so that the elevation error does not exceed 3mm. If it exceeds the error range, it needs to be calibrated again;

[0147] ⑦ When calibrating the laser station, the level point of the laser station should be 40-80m away from the level point where the laser station is set up. The laser station instrument height calibration shall not be carried out within 20m of the laser station.

[0148] ⑧ When the instrument is set up and the laser station instrument is calibrated, confirm whether the rover height is entered correctly. After the laser station height calibration is completed, select another 2 to 3 leveling points to check whether the height is correct;

[0149] ⑨After the GPS base station and laser elevation base station are set up, use the mobile station to stake out 2-3 control points and leveling points, check the three-dimensional coordinates, and confirm that all instruments are working properly and all data are accurate;

[0150] Step 5: Import design data, including the following steps:

[0151] (1) Importing design and construction data into the millimeter GPS mobile station: Import the prepared paving surface data (.TN3 format) and road data (.RD3 format) into the mobile station hand, and load the design data into the hand;

[0152] (2) On-site original ground verification: After the data is loaded, several cross sections are staked out to measure whether the surface data is correct and confirm whether the loose paving thickness is the designed loose paving thickness, so as to verify the accuracy of the elevation, transverse slope, longitudinal slope and other data of the designed data;

[0153] (3) Importing construction data into the paver control system: After the data is confirmed to be correct, export the surface data, control points, leveling points and other data and copy them to a USB flash drive (generally, the construction date of the day is used as the project file name); before the paver starts working, connect the GX-60 control box power supply, turn on the power and copy the project file exported from the hand to the software root directory; open the 3DMC software, select the project data according to the file name date, and load it;

[0154] Step 6: Automatic paving, specifically including the following steps:

[0155] (1) After the equipment is set up and calibrated, all data are imported into the mobile station and GX-60 control box. After all preparations are completed, paving operations can be carried out;

[0156] (2) Using the mobile station, the construction road to be paved is marked out based on the designed width and offset, and the formwork is supported;

[0157] (3) Before the paver is in place, use the mobile station to measure and place the screed pads so that the screed is on the designed loose paving surface when the paver is in place, and adjust the left and right scale readings of the paver;

[0158] (4) When the paver is ready, instruct the material truck to dump and spread the material, and start the paver. Turn off the automatic mode first, and walk 2m to 3m to measure with the mobile station to see whether the paved loose surface coincides with the designed surface. If there is a deviation, manually raise and lower the scales on both sides to make the elevation and cross slope of the paving surface reach the designed value;

[0159] (5) When the elevation, cross slope and other parameters are close to the design values, turn on the automatic switch to perform automatic leveling and paving;

[0160] (6) As the paver moves, the distance from the laser station at the starting position continues to increase. When the distance reaches about 100m, the laser receiving channels of the mobile station and the automatic paving system of the paver are changed to the laser station closer to the working area of ​​the paver;

[0161] (7) The laser stations are alternately set up in the paving direction to carry out continuous and uninterrupted paving operations;

[0162] (8) Use the mobile station to measure in real time whether the paving surface is consistent with the design, and make timely adjustments when fluctuations occur;

[0163] (9) When it is necessary to determine the loose paving coefficient, collect the elevation of the original ground points in advance. After the paving is completed and before rolling, measure the loose paving elevation. After rolling, measure the elevation after compaction. After the paving and rolling are completed, export the measured data.

[0164] (10) During the paving process, always pay attention to the automatic paving system receiving laser elevation information. If there is an interruption or no signal, turn off the automatic switch in time and pay attention to whether the paver scale fluctuates. Turn on the automatic switch after there is a signal.

[0165] (11) When the automatic paving control system on the paver selects the laser elevation information, the receivers on the left and right sides must select the laser signal emitted by the same laser reference station and must not receive laser signals from two instruments at the same time;

[0166] (12) When the paver is paving, the connected laser reference station should not be located on the road section being rolled. When the roller vibrates, the laser elevation information emitted by the laser reference station will fluctuate. Therefore, the laser elevation signal emitted by the laser reference station far away from the rolling section should be selected;

[0167] (13) When the paver is moving forward, the laser reference station should be set up alternately in the forward direction. After each setting, the instrument height should be calibrated. After the calibration is completed, the instrument height and point number should be recorded, and the corresponding data should be modified in the GX-60 control box;

[0168] (14) When adjusting the scale of the paver, it should be raised or lowered slowly and evenly, and should not be raised or lowered suddenly to prevent the formation of potholes that affect the flatness of the paving surface;

[0169] (15) After the construction is completed, the coordinate information and elevation information measured during the construction process are exported to facilitate the summary and analysis of the problems encountered during the construction process;

[0170] Step 7: rolling; the rolling scheme is as follows:

[0171] (1) The road section rolling scheme where the roller can start vibration

[0172] Initial rolling: Use 13t double steel wheels with full width static rolling once, with a rolling speed of 1.5-1.7km / h;

[0173] Recompaction: ① 22t single steel wheel static pressing once, vibration rolling twice, rolling speed 2-2.5km / h;

[0174] ② 26t single steel wheel vibrating rolling once, static rolling once, rolling speed 2-2.5km / h;

[0175] Final rolling: 30t tire roller rolling the full width twice, rolling speed 2-2.5km / h;

[0176] (3) Rolling plan for sections where the roller cannot start vibration

[0177] Initial rolling: Use 13t double steel wheels with full width static rolling once, with a rolling speed of 1.5-1.7km / h;

[0178] Re-pressing: ①22t single steel wheel static pressing 2 times, rolling speed 2-2.5km / h;

[0179] ②26t single steel wheel static pressing 2 times, rolling speed 2-2.5km / h;

[0180] ③36t single steel wheel static pressure 2 times, rolling speed 2-2.5km / h;

[0181] Final rolling: 30t tire roller rolling the full width twice, rolling speed 2-2.5km / h;

[0182] Step 8: Testing compaction, curing, and acceptance; specifically includes the following steps:

[0183] (1) The compaction degree requirement for the cement-stabilized crushed stone subbase of expressways is 97%, and the compaction degree requirement for the base layer is 98%. The sections that have been rolled should be inspected in a timely manner, and those that fail to meet the requirements should be re-compacted in a timely manner until the compaction degree meets the requirements;

[0184] (2) For sections that have been rolled and have passed the compaction test, the sections are covered with permeable geotextiles and watered for curing, and traffic is closed for curing for more than 7 days. The geotextiles are then uncovered 2 days before the next construction process.

[0185] (3) For road sections that have completed maintenance, each sub-item shall be inspected and accepted in accordance with the Highway Engineering Quality Inspection and Assessment Standards.

[0186] Example 2 Benefit Analysis

[0187] 1. Economic benefits

[0188] In the construction scheme of 3D intelligent paving at the base of highway engineering, the measurement and layout does not require the cooperation of labor personnel. The construction layout is accurate, reliable and fast, which effectively improves the construction efficiency. During the construction process, various quality indicators are tested in real time to strengthen process management and control. Compared with the traditional hanging wire rope construction scheme, this method can save a lot of labor and materials, shorten the construction period and save construction costs. The following table compares the economic benefits of the hanging wire rope method and 3D intelligent paving.

[0189] Table 1 Comparison of economic benefit analysis

[0190]

[0191]

[0192] Through economic benefit analysis and comparison: the use of this construction method can save 7,000 yuan in material costs, 600 yuan in labor costs per kilometer per layer, and shorten the construction period by 0.2 days.

[0193] 2. Social Benefits

[0194] Table 2 Comparison of key quality control indicators and material loss

[0195] content Wire rope method Millimeter GPS automatic paving system Flatness(mm) 5～8 3～5 Material loss 3.5％ 2％ Height control(mm) ±15 ±5

[0196] The use of 3D intelligent paving construction method for highway engineering base has effectively improved the connection between construction sections, and the quality control of inorganic binder paving process has been significantly improved, achieving all-weather refined construction, saving construction time, and improving driving comfort. It has significant social benefits and is worthy of promotion.

[0197] Embodiment 3 Application Example

[0198] 1. Application Example 1

[0199] 1.1 Project Name: G316 Changle to Tongren Highway Liangdang County Yangdian (Gansu-Shaanxi Border) to Hui County Lijiahe Expressway LH-GSLQSGSZBB Contract Section

[0200] 1.2 Project location: Longnan City, Gansu Province

[0201] 1.3 Project cost: RMB 285.127 million

[0202] 1.4 Construction date: Started on June 11, 2018 and completed on August 25, 2019.

[0203] 1.5 Project Overview: The total length of this project is 33.225km. The main line is built according to the standard of a four-lane expressway. The designed driving speed is 80km / h for the newly built section from Yangdian to Huixian Yinxing, and 60km / h for the first-level high-speed section from Yinxing to Lijiahe using the Shitian Road Huixian connecting line. The roadbed width is 24.5m (integral) and 12.25m (separated). The entire line adopts asphalt concrete pavement, and the vehicle load level is highway-Ⅰ.

[0204] Main works of pavement engineering: 18cm cement stabilized subbase 510498m 2 ; 20cm cement stabilized gravel base 83098m 2 ; 34cm cement stabilized gravel base 398033m 2 ; 8cm dense graded asphalt gravel ATB-25 bottom layer 334432m 2 ; 6cm medium-grained asphalt concrete AC-20 middle surface layer 42658m 2 ; 5cm medium-grained asphalt concrete AC-20 middle surface layer 13170m 2 ; 4cm fine-grained asphalt concrete AC-13 top layer 55828m 2 ; 6cm modified asphalt concrete superpave-20 middle surface layer 855899m 2 ; 4cm modified asphalt concrete superpave-13 upper layer 627409.7m 2 ; 4cm flame retardant modified asphalt concrete superpave-13 top layer 228490m 2 .

[0205] 2. Application Example 2

[0206] 2.1 Project Name: G1816 Wuhai-Maqin Expressway Jingtai to Zhongchuan Airport Section Highway Project JZ9 Contract Section

[0207] 2.2 Project location: Yongdeng, Lanzhou City, Gansu Province

[0208] 2.3 Construction date: January 1, 2018 - July 31, 2019

[0209] 2.4 Project cost: RMB 338,480,800

[0210] 2.5 Project Overview: The total length of the project is 6.159km, including 2.7km of main ramp, 2.809km of general ramp, and 0.65km of relocated provincial road. One new super-large bridge, three large bridges, one medium bridge, and 10 culverts will be built, of which the main ramp viaduct is 1126.46m long, with a design speed of 60km / h, four lanes in both directions, and a lane width of 3.75m.

[0211] Main works of pavement engineering: 18cm cement stabilized subbase 85985m 2 ; 34cm cement stabilized gravel base 82110m 2 ; 20cm cement stabilized gravel base 33940m 2 ; 20cm cement stabilized gravel base 32319m 2 ; 8cm asphalt gravel surface layer 69431m 2 ; 4cm medium-grained asphalt concrete 30558m 2 ; 6cm modified asphalt concrete 98440m 2 ; 4cm modified asphalt concrete 98440m 2 .

[0212] 3. Application Effect

[0213] With the rapid development of the highway construction industry, refined and automated construction has become the development direction of the highway construction industry. According to the flatness detection data of the construction site, the 3D intelligent paving construction method is used for base construction, with high positioning accuracy. The differential positioning can achieve the accuracy of centimeters in the plane and millimeters in the elevation. According to the flatness detection data of the construction site, the maximum single-point flatness detection value is 3mm, the elevation control accuracy reaches ±5mm, the thickness control is accurate, and the construction mixture loss is 2%. This method can effectively improve driving comfort, save materials, extend the service life of the road, and achieve good economic and social benefits.

[0214] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A 3D intelligent paving construction method for highway engineering base, characterized in that: The steps include: Step 1: Preliminary data preparation, including original design data; Step 2: Design data production; Step 3: Arrangement of control points and leveling points; Step 4: Instrument installation; Step 5: Import design data; Step 6: Automatic paving; Step 7: rolling; Step 8: Check compaction, curing and acceptance.

2. A highway engineering base 3D intelligent paving construction method according to claim 1, characterized in that: In step 1, the original design data consists of 4 parts: (1) Line, curve and corner table: The main input elements are the starting point coordinates, stake number, intersection point coordinates, stake number and curve element value; (2) Longitudinal slope and vertical curve table: The main input elements are the starting point elevation, pile number and vertical curve elements; (3) Roadbed design table: The main input elements are mileage pile number, roadbed width, and roadbed cross slope; (4) Stake-by-stake coordinate table: Use the stake-by-stake coordinates to check whether the input road is correct: (5) Design and construction data statistics: According to the design drawings and actual conditions, the pile numbers of different auxiliary structures are counted and organized in a unified manner to prepare for the production of design data.

3. A highway engineering base 3D intelligent paving construction method according to claim 1, characterized in that: In step 2, the design data is produced by editing the horizontal curve, vertical curve, cross slope and width of the road in Topcon 3D-Office software according to the original design data, which specifically includes the following steps: (1) Load 3Doffice to create a new project and a new road project; (2) After the new road project is completed, click Road Project (Alignment) / click Horizontal Center Line to open the input interface, and enter data in the element method format according to the line curve and angle table; (3) After the horizontal profile is completed, click Vertical Profile to open the input interface and enter the data in a certain format according to the longitudinal slope vertical curve table; (4) After the vertical alignment is completed, click on the cross slope model (Templates) and enter the cross slope model of the normal section and the super-elevated section according to the roadbed design table; (5) After adding the cross slope model, click OK, then add the start and end pile numbers and the corresponding cross slope, left width, and right width to be constructed, and click OK; (6) After adding the cross slope data, click the Generate TIN from 3Dalignment option, enter the grid spacing, the recommended value for straight segments is 1.5m, and the recommended value for superelevated sections is 0.2m, and click OK to generate the surface data; (7) Calculate the height difference according to different positions and slopes, check whether the data is correct, and save the data for future use; (8) When inputting cross slope data, all mileages of cross slope changes must be input without omission, wrong input or skipping; (9) When making design data, the input structure layer width should be 1m wider than the maximum design width on both sides to prevent the automatic paving system from being unable to obtain surface data information and ensure that the paving does not exceed the designed surface width; (10) When making surface data of a normal section, i.e. a section with a constant cross slope of the roadbed, the grid spacing should be set to 1.5 m when forming the network data; if the spacing is too small, the data will be too large and will not work properly when imported into the mobile station and GX-60; (11) When preparing surface data for a slope-changing section, i.e. a section where the cross slope changes or a superelevation section, in order to ensure the continuity of the screed plate when changing the slope during paving, the grid spacing should be 0.1-0.2 m, and the length of each section should not exceed 300 m; when the length of the surface data to be prepared exceeds 1000 m, it is advisable to prepare it in sections and switch the data during paving; (12) The produced design data should be classified and clearly marked to facilitate searching and modification.

4. A highway engineering base 3D intelligent paving construction method according to claim 1, characterized in that: In step three, the control point and level point layout includes the following steps: (1) Site inspection in the construction area: select a flat, hard, and unobstructed location around the construction site to set up control points and leveling points; (2) Arrangement of field control points and leveling points: After the site survey is completed, the positions of the control points and leveling points are determined and arranged; the requirements for the arrangement of control points and leveling points are as follows: ① The control points should be arranged in a grid pattern in the construction area and cover the entire construction area; ② The layout of control points should take into account the establishment of GPS base stations. The control points should cover the construction area and be no more than 500 meters away from the construction area; ③ When laying out control points, keep them away from high-voltage lines, houses, rivers, gullies, etc. to prevent them from affecting the GPS base station’s reception of satellite signals; ④ When laying out the leveling points, the laser station should be set up during paving to ensure that the laser information emitted by the laser station can be received by the MC-R3 receiver on the paver; ⑤ The leveling points are usually laid out on both sides of the construction road. Since the laser emission range is within ±5m of the horizontal plane where the transmitter is located, and considering the influence of the longitudinal slope of the road, the leveling point is generally 1 to 2m higher than the top surface of the roadbed; ⑥ To ensure the continuous and uninterrupted progress of the construction, two laser elevation reference stations need to be set up alternately. To ensure the elevation accuracy, the spacing between the leveling points is controlled at about 100m; ⑦ When laying out the leveling points, choose a flat, hard, unobstructed location at least 20 meters away from the construction section; ⑧ When arranging control points and leveling points, choose a hard, flat, unobstructed location. The distance between control points should be between 300 and 500 meters, and the distance between leveling points should be about 100 meters. A temporary leveling point should be added between the leveling points to calibrate the height of the laser station instrument. A temporary leveling point should be set every 50 meters. ⑨ Control points and leveling points should be placed in places that are not easily disturbed and reinforced with concrete; (3) Surveying and setting of control points and leveling points: The surveying and setting of control points shall be carried out in accordance with the accuracy requirements of the first-class traverse, and the surveying and setting of leveling points shall be carried out in accordance with the accuracy requirements of the fourth-class leveling.

5. A highway engineering base 3D intelligent paving construction method according to claim 1, characterized in that: In step 4, the instrument installation specifically includes the following steps: (1) Installation of GPS base station ① Before paving, select the control point closest to the construction section to set up a millimeter GPS reference station; ②Align the leveling instrument and measure the height of the instrument; ③ Turn on the base station, wait for the normal working prompt voice to sound, connect to the mobile station hand via Bluetooth, and set the base station's point number, instrument height, radio channel and other parameters; ④Observe the battery power, satellite reception and radio signal transmission of the base station. After all indicators are working normally, connect the mobile station receiver to see if it can work normally. ⑤ Locate other known control points, and control the plane position error within ±2cm to verify whether the GPS base station is set up correctly; (2) Installation of PZL-1 laser elevation reference station ① Before starting construction, determine the location of the first laser station. Select a leveling point 20-30m away from the side and rear of the paver as the first laser station. If the first laser station is set up too far away, it is easy to cause inaccurate elevation information. If it is set up on the side or front of the paver, the laser elevation information is easily blocked, which may cause the automatic paving system to fail to work properly. ② After determining the location of the leveling point, set up the laser reference station on the tripod, first perform automatic leveling of the instrument, and accurately center the leveling point; ③Measure the installation height of the laser station instrument; ④Connect the hand to the laser station through Bluetooth, and set various parameters such as instrument height, model, station location, laser transmission channel, etc. ⑤ Connect the mobile station to a position 5m away from the laser station, align the mobile station laser receiver with the laser station, and check whether the laser station is working properly; ⑥ After the laser station is working properly, place the mobile station at the nearest leveling point, and stake out the three-dimensional coordinates of the leveling point so that the elevation error does not exceed 3mm. If it exceeds the error range, it needs to be calibrated again; ⑦ When calibrating the laser station, the level point of the laser station should be 40-80m away from the level point where the laser station is set up. The laser station instrument height calibration shall not be carried out within 20m of the laser station. ⑧ When the instrument is set up and the laser station instrument is calibrated, it is necessary to confirm whether the mobile station instrument height is input correctly. After the laser station instrument height calibration is completed, select another 2 to 3 leveling points to check whether the instrument height is correct; ⑨After the GPS base station and laser elevation base station are set up, use the mobile station to lay out 2-3 control points and leveling points, check the three-dimensional coordinates, and confirm that all instruments are working properly and all data are accurate.

6. A highway engineering base 3D intelligent paving construction method according to claim 1, characterized in that: In step 5, the design data import specifically includes the following steps: (1) Importing design and construction data into the millimeter GPS mobile station: Import the prepared paving surface data (.TN3 format) and road data (.RD3 format) into the mobile station hand, and load the design data into the hand; (2) On-site original ground verification: After the data is loaded, several cross sections are staked out to measure whether the surface data is correct and confirm whether the loose paving thickness is the designed loose paving thickness, so as to verify the accuracy of the elevation, transverse slope, longitudinal slope and other data of the designed data; (3) Importing construction data into the paver control system: After the data is confirmed to be correct, export the surface data, control points, leveling points and other data and copy them to the U disk; before the paver works, connect the GX-60 control box power supply, turn on the power and copy the project files exported from the hand to the software root directory; open the 3DMC software, select the project data according to the file name date, and load it.

7. A highway engineering base 3D intelligent paving construction method according to claim 1, characterized in that: In step six, the automatic paving specifically includes the following steps: (1) After the equipment is set up and calibrated, all data are imported into the mobile station and GX-60 control box. After all preparations are completed, paving operations can be carried out; (2) Using the mobile station, the construction road to be paved is marked out based on the designed width and offset, and the formwork is supported; (3) Before the paver is in place, use the mobile station to measure and place the screed pads so that the screed is on the designed loose paving surface when the paver is in place, and adjust the left and right scale readings of the paver; (4) When the paver is ready, instruct the material truck to dump and spread the material, and start the paver. Turn off the automatic mode first, and walk 2m to 3m to measure with the mobile station to see whether the paved loose surface coincides with the designed surface. If there is a deviation, manually raise and lower the scales on both sides to make the elevation and cross slope of the paving surface reach the designed value; (5) When the elevation, cross slope and other parameters are close to the design values, turn on the automatic switch to perform automatic leveling and paving; (6) As the paver moves, the distance from the laser station at the starting position continues to increase. When the distance reaches about 100m, the laser receiving channels of the mobile station and the automatic paving system of the paver are changed to the laser station closer to the working area of ​​the paver; (7) The laser stations are alternately set up in the paving direction to carry out continuous and uninterrupted paving operations; (8) Use the mobile station to measure in real time whether the paving surface is consistent with the design, and make timely adjustments when fluctuations occur; (9) When it is necessary to determine the loose paving coefficient, collect the elevation of the original ground points in advance. After the paving is completed and before rolling, measure the loose paving elevation. After rolling, measure the elevation after compaction. After the paving and rolling are completed, export the measured data. (10) During the paving process, always pay attention to the automatic paving system receiving laser elevation information. If there is an interruption or no signal, turn off the automatic switch in time and pay attention to whether the paver scale fluctuates. Turn on the automatic switch after there is a signal. (11) When the automatic paving control system on the paver selects the laser elevation information, the receivers on the left and right sides must select the laser signal emitted by the same laser reference station and must not receive laser signals from two instruments at the same time; (12) When the paver is paving, the connected laser reference station should not be located on the road section being rolled. When the roller vibrates, the laser elevation information emitted by the laser reference station will fluctuate. Therefore, the laser elevation signal emitted by the laser reference station far away from the rolling section should be selected. (13) When the paver is moving forward, the laser reference station should be set up alternately in the forward direction. After each setting, the instrument height should be calibrated. After the calibration is completed, the instrument height and point number should be recorded, and the corresponding data should be modified in the GX-60 control box; (14) When adjusting the scale of the paver, it should be raised or lowered slowly and evenly, and should not be raised or lowered suddenly to prevent the formation of potholes that affect the flatness of the paving surface; (15) After the construction is completed, the coordinate information, elevation information, etc. measured during the construction process are exported to facilitate the summary and analysis of the problems encountered during the construction process.

8. The method for 3D intelligent paving of a highway engineering base according to claim 1 is characterized in that: In step seven, the rolling includes the following schemes: (1) The road section rolling scheme where the roller can start vibration Initial rolling: Use 13t double steel wheels with full width static rolling once, with a rolling speed of 1.5-1.7km / h; Recompaction: ① 22t single steel wheel static pressing once, vibration rolling twice, rolling speed 2-2.5km / h; ② 26t single steel wheel vibrating rolling once, static rolling once, rolling speed 2-2.5km / h; Final rolling: 30t tire roller rolling the full width twice, rolling speed 2-2.5km / h; (2) Rolling plan for sections where the roller cannot start vibration Initial rolling: Use 13t double steel wheels with full width static rolling once, with a rolling speed of 1.5-1.7km / h; Re-pressing: ①22t single steel wheel static pressing 2 times, rolling speed 2-2.5km / h; ②26t single steel wheel static pressing 2 times, rolling speed 2-2.5km / h; ③36t single steel wheel static pressure 2 times, rolling speed 2-2.5km / h; Final compaction: 30t tire roller rolls the entire width twice at a speed of 2-2.5km / h.

9. A highway engineering base 3D intelligent paving construction method according to claim 1, characterized in that: In step eight, the compaction detection, curing, and acceptance include the following steps: (1) The compaction degree requirement for the cement-stabilized crushed stone subbase of expressways is 97%, and the compaction degree requirement for the base layer is 98%. The sections that have been rolled should be inspected in a timely manner, and those that fail to meet the requirements should be re-compacted in a timely manner until the compaction degree meets the requirements; (2) For sections that have been rolled and have passed the compaction test, the sections are covered with permeable geotextiles and watered for curing, and traffic is closed for curing for more than 7 days. The geotextiles are then uncovered 2 days before the next construction process. (3) For road sections that have completed maintenance, each sub-item shall be inspected and accepted in accordance with the Highway Engineering Quality Inspection and Assessment Standards.

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