Regarding broken pile heads

Generally, cast-in-place piles are made a little higher than the designed elevation, as it is difficult to ensure good quality at the end of the pouring process. The amount by which the pile head is cut back depends on the designed elevation of the pile top; once that elevation is reached, the pile top is first leveled before further testing is carried out. Load tests, low-strain tests, and high-strain tests all require a flat pile top, whereas core drilling and acoustic wave transmission methods do not have such a requirement

Supervision, Inspection, and Key Construction Points I. Scope of Supervision and Duration of Supervision A **supervision and management system** is implemented for the quality of highway projects. For all new construction, renovation, and major/mid-scale repair projects, quality supervision and management shall be carried out by the Quality Supervision Department. 　　The quality supervision period for highway construction projects spans from the completion of supervision procedures prior to the project’s commencement to the evaluation of the project’s quality grade upon completion. 　　II. Procedures for supervision and inspection 　　1. Seven days before submitting an application for a ‘Start of Work Report’, the construction unit shall fill out the ‘Application for Quality Supervision of Highway Projects’ and submit it to the quality supervision department to go through the supervision application procedures. 　　2. When applying for the supervision procedures, the construction unit shall provide the Quality Supervision Department with the following documents and materials: 　　(1) The approval documents for the project, and a copy of the construction contract ； 　　⑵The construction design drawings and technical specifications for this line ； 　　⑶Copies of the Supervision Contract, the supervision work plan, and copies of the qualification certificates of the supervision unit and supervisors ； 　　⑷List of equipment and technical personnel in the supervision unit’s site laboratory ； 　　⑸List of equipment and technical personnel in the construction unit’s on-site laboratory, list of the main technical supervisors involved in the construction of this project, as well as those responsible for the quality inspection system, along with copies of their qualification certificates ； 　　⑹A copy of the construction contractor’s qualification certificate, along with the contractor’s construction plan and a list of the main mechanical equipment. 　　3. Participate in the bidding processes for construction projects ； Supervise and inspect construction and supervision units to establish and improve quality assurance systems. 　　4. Check whether the arrival of personnel and equipment from the construction and supervision units is in line with the construction contract (bid document). 　　5. Conduct irregular spot checks on the work of the testing laboratories and quality control departments of the construction and supervision units. 　　6. Conduct sampling inspections of finished products, semi-finished products, and various construction materials at the site. 　　7. Conduct on-site inspections of the construction quality of various sub-projects and test sections, examine the project inspection documents prepared by the construction unit and the on-site supervisor, and patrol the construction site to keep track of the progress of the project quality at all times. 　　8. Inspect the organizational management at the construction site, review the design modification procedures, and ensure strict supervision over standardized, regulated, and civilized construction practices. 　　9. Supervise and inspect the work procedures, quality control, on-site supervision by supervisors, and independent sampling inspections at the construction site. 　　10. For the quality issues identified during inspections, a “Notice of Opinions on Random Inspections of Highway Project Quality in Hebei Province” shall be issued promptly, and follow-up inspections shall also be carried out. 　　11. After the self-inspection of a particular construction task shows it to be satisfactory and the samples inspected by the supervisor are approved, a written application must be submitted to the quality supervision department for a quality assessment. The supervision department shall arrive at the construction site within 48 hours of receiving the application, conduct a quality assessment of that task in accordance with the \"Hebei Province Highway Project Quality Inspection and Evaluation Standards\", and issue a quality assessment report for that task ； The frequency of application for appraisal shall be no less than 30% of the total project. 　　12. Organize joint inspections of highway project quality at appropriate times to rank the quality levels. The inspection is carried out on the section where all construction equipment has been removed from the site, using a random sampling approach. The aspects examined include various technical specifications, the appearance of the equipment, internal documentation, whether the operations during the construction process are carried out in a proper manner, as well as the level of compliance with standards, regulations, and best practices for civilized construction. 　　13. After the project is delivered, organize a quality assessment of the project. 　　14. Conduct a quality follow-up inspection on the project one year after it is put into use. 　　III. Key Points for Supervision and Inspection of Highway Projects The following items represent the key points for control and supervision of various sub-projects; all construction units must exercise strict control over them, and in cases where there are deficiencies, the relevant standards shall apply. 　　A test section should be constructed before the official commencement of each sub-project, and a written summary report on the test section should be prepared based on the construction progress. In addition to fulfilling the mandatory requirements specified in the \"Hebei Province Highway Engineering Quality Inspection and Evaluation Standards,\" the following aspects are also included: ① Loose-fill coefficient; ② Loose-fill thickness; ③ Compacted thickness; ④ Selection of rollers and the sequence in which they are used during construction; ⑤ Number of passes for rolling; ⑥ Degree of compaction; ⑦ Speed at which the rollers move. These elements are used to verify whether the combination of construction equipment, the workflow, and various technical parameters meet the requirements of the standards. The pass rate for each individual indicator must be no less than 90 points. The construction unit must notify the quality inspection personnel to arrive and inspect the test section; construction of the next phase shall not proceed unless the test section is approved. 　　(1) Road Engineering 　　1. Subgrade construction phase 　　① During the subgrade clearing work for new sections, it is essential to completely remove any layers containing organic matter. 　　②The use of mixed soil containing sand and clay, soil with many grass roots and debris, and humus soil is prohibited. 　　③Appropriate compaction standards are adopted according to different types of soil. The construction unit shall prepare separate records for each construction section (layer) with different standard dry unit weights and optimal moisture contents, to facilitate inspection. 　　④Stairs must be excavated on the slopes of widened old roads, with stakes set along the foot of the slope. 　　⑤Strictly control the moisture content of the fill soil; overly wet soil should first be turned over and dried before being leveled and compacted. It is forbidden to use the incorrect practice of treating softened sections by simply drying them without turning them over. 　　⑥The backfill foundation of bridges and culverts must be compacted effectively; if necessary, lime-soil or lime-fly ash mixtures should be used for backfilling to ensure that the filled area does not settle. 　　⑦Quality inspection personnel conduct 100% testing of subgrade deflection, with the deflection value at the top surface of the roadbed not exceeding 247 (1% mm) (using the vehicle-following testing method). 　　⑧For high-fill sections, elevation checks are conducted every three layers of soil compaction. 　　⑨Each layer of fill material must have a smooth surface, be compact with no areas that are soft or spongy, ensure slope stability, and have smooth curves. ⑩ The roadbed filling should be widened by 30–50 cm on each side as required by the standards, in order to meet the requirements for slope reduction. 　　Supervisors shall conduct random inspections of the centerline deviation and elevation. 　　2. Quality control of lime soil 　　① Inspect the raw materials ； The lime grade must be at least grade 3; the amount of lime used in construction should be 1% higher than that specified in the design ； Lime should be slaked 10 days in advance, and the slaked lime should be used up within 1 month. If cement is used for treatment, road cement with a final setting time of over 6 hours should be employed. 　　②First, compact the prepared soil and level it at the measurement points; for spreading the ash, it should be done manually by stacking it in grids. 　　③During mixing, a dedicated person should be assigned to inspect the mixture as it is being prepared, at intervals of 5 to 10 meters, to check for any layers of plain soil or areas where mixing has been neglected. The mistaken practice of deepening mixing to prevent delamination should not be adopted. Clay lumps are not easy to crush; therefore, the multiple mixing method specified in the standards should be used, that is, compacting first and then crushing followed by another mixing step. 　　④For the final smoothing pass, work with soil still present; avoid making corrections. 　　⑤The joint areas should be constructed using the hand-fitting method, and the construction joints between different structural layers should be spaced at least 10 meters apart. 　　⑥The lime-soil mixture should be kept moist for at least 7 days; if conditions permit, it can be covered with plain soil. 　　Sampling inspections during the application of ash should be strengthened. 　　3. Lime-fly ash macadam (stabilized macadam): The gradation of the aggregates must meet the specified requirements; there should be no aggregates with sizes exceeding the allowed limits, and all parameters of the aggregates must comply with the standard specifications. The construction unit should conduct self-inspections every morning. 　　Supervisors should conduct random inspections from time to time. 　　Before paving with lime-fly ash macadam, any areas with insufficient strength in the lime-soil mixture, thick layers, or looseness must be thoroughly cleaned, and an appropriate amount of water should be applied to keep the surface of the underlying layer moist. 　　Lime, fly ash, and similar materials need to be screened, and during the rainy season, covering measures should be taken for such materials. The material yard should not be too small; materials should be stored in a proper manner to facilitate use, and efforts should be made to avoid situations where materials brought in are left unused for long periods of time. 　　Conduct sieve testing on the aggregates as appropriate, and adjust the mix ratio in a timely manner. 　　Check whether there is any mixing of raw materials in the material yard, and ensure that there is someone monitoring the discharge from each hopper; any blockages should be addressed immediately. 　　In areas where there has been excessive moisture, dryness, or delamination, the material must be removed and replaced. The joints must be smooth and checked with a 3-meter straightedge; any deviation greater than 5 mm requires correction ； Vertical joints are prohibited; joints must be spaced at least 10 meters away from the construction joints in the underlying layer. 　　Rolling must be carried out continuously; samples should be taken for testing immediately after compaction, and additional compaction should be performed if the degree of compaction is insufficient. 　　From the addition of water for mixing to rolling into shape, the process for stabilized macadam must be completed within 3 hours. 　　Pay attention to moisture retention and proper maintenance, strictly control traffic to prevent the surface from becoming loose or developing pits. 　　4. Penetrating oil: Apply it in accordance with the specified amount; the quantity used should not be excessive, and any accumulated oil should be removed manually ； Sealant and bonding agent must be applied evenly to the edges, in order to protect curbs and crash barriers. At major level crossings, an appropriate amount of gravel should be scattered as needed to strictly control traffic flow. 　　5. Asphalt concrete surface layer: Strengthen the inspection of raw materials; the samples sent for testing should be identical to those used in actual construction, and the use of weathered rock is strictly prohibited. 　　Before starting work, the supervision team shall conduct sampling tests on the materials. 　　②Asphalt should be supplied in accordance with the requirements of the owner and the bidding documents; all necessary inspection items must be carried out, and testing must be done for each truckload. Asphalt of different types must not be mixed together. And strengthen the dust-proof protection measures for the oil tank. 　　③The paving temperature should be no lower than 130°C to 140°C; it must not drop below 140°C when the temperature is below 10°C. For whatever reason, the mixture must not be used once it has cooled to the specified temperature. 　　④The paver and a person check the thickness and flatness ； Send back feedback in a timely manner to guide the construction. 　　⑤Rolling must be used to completely eliminate the marks left by the suspension beam; the unpaved asphalt surface should not be stepped on. Rolling should be carried out at high frequency and low amplitude, and vibration is prohibited when passing over bridges. 　　⑥The flatness at the joints should be carefully checked (it should not exceed 3 mm). ⑦Paving of asphalt concrete surfaces on county and rural roads should not take place after October 15. 　　5. Cement concrete surface layer: The construction unit shall check the cement concrete mix ratio daily. 　　Supervisors will conduct random inspections from time to time. 　　②Check that the base layer is clean and wet it with water. 　　③Check whether the stiffness and straightness of the template meet the requirements of the specifications. 　　④The cutting time should be appropriate to prevent board or corner breakage. 　　⑤The time and depth of texturing should meet the requirements specified in the design and standards. 　　⑥Strengthen maintenance to prevent the occurrence of drying shrinkage cracks. 　　⑦It is necessary to enclose the area with water for 14 to 21 days for curing; traffic can be allowed only after it reaches the designed strength. 　　(II) Bridge and culvert projects 　　Sand and gravel materials 　　For sand, it is necessary to use medium or coarse sand with good gradation, hard texture, and clean particles ； The crushing value of the stone material must meet the requirements. 　　Reinforcing bars and cement: The manufacturers must meet the requirements set by the client and those specified in the tender documents; they must also have original factory certificates and submit their products for testing as required. 　　Cement concrete: The mix ratio for cement concrete must be based on a report issued by a testing and inspection center or approved by such a center. The laboratory of the construction unit must check the mix ratio and slump of the concrete daily, and take samples in accordance with relevant standards to determine its strength. The test specimens must be cured under standard conditions ； Large-area concrete curing should be covered with felt. 　　During the construction preparation phase 　　① Carry out work to verify level points and control piles. 　　②Complete all raw material tests. 　　5. During construction period Lower structure: ① Drilling: a. Strictly control the drilling location. 　　b. The drilling rig must be stable and vertical. 　　c. Aperture, hole depth, and pile position are the key items for inspection. 　　d. The mud specific gravity and sand content must meet the specification requirements. 　　②Perfusion: a. Check the thickness of the sediment at the bottom of the hole; it must meet the specified requirements. 　　b. The rebar framework should be vertical and must not touch the well wall. 　　c. Strictly control the depth of catheter insertion to prevent broken piles or buried tubes. 　　d. The strength at the time of breaking the pile head should be sufficient for more than 7 days; the breaking height should be no less than 80 cm. The rebar in the pile should be straight, with a bending angle not exceeding 45°, and the top surface of the pile should have a bun-like shape. 　　③Connector post: a. The formwork is installed in the correct position and is vertical. 　　b. The template tie rods are tightened diagonally simultaneously using tensioners. 　　c. Concreting should be carried out using conduits, and vibration must be thorough. 　　④Lantai masonry: a. The masonry materials must meet the specifications; substandard stones shall not be used. 　　b. Before construction, check the elevation and geometric dimensions of the foundation base; conduct a bearing capacity assessment as necessary, and it is strictly prohibited to over-excavate and fill in loose soil. 　　c. The soil on the surface of the blocks should be washed clean. 　　d. Build in layers, ensure proper grouting, and stagger the vertical joints. 　　e. Settlement joints must be vertical and continuous. 　　f. During the construction process, attention should be paid to checking the visual quality; the masonry surface must be smooth, with joints that are regular and even. 　　⑤Pier cap or cover beam: a. The formwork should be installed in an accurate and vertical position, with strict control to prevent uneven surfaces resulting from excessive expansion of the concrete. 　　b. The concrete should be vibrated thoroughly during pouring to ensure compactness. 　　c. Slurry leakage is likely to occur at the bow slope of the cap beam, so strict control over formwork installation is required. 　　d. The top surface of the cap beam should be smooth, the positions of the anchor bolts should be accurate, and the elevation at the supports must be strictly controlled. 　　Superstructure 　　① Slab: 　　a. The foundation should be treated with lime-soil to ensure integrity and prevent the slab from cracking. 　　b. The geometric dimensions shall not be larger than the design dimensions and must meet the specification requirements. 　　c. Pouring should be carried out in layers, continuously and in a sequential manner at a certain thickness. 　　d. The position of the corrugated pipe for embedding the prestressed rebar must be accurate. 　　e. The anchorage plates of prestressed steel bars shall be inspected in accordance with the specifications. 　　f. The prestressing tensioning equipment must be calibrated once a year as required. 　　g. For prestressed hollow slabs, a negative camber in the base should be provided according to the camber height; toothless saws must be used for cutting the prestressed steel strands. 　　h. The position of the pre-embedded connection bars in the slotted joints should be accurate, to prevent damage to the beam structure when these bars are removed due to being buried too deep. 　　i. Prevent excessive vibration at the bottom of the plate and avoid the formation of rod patterns. 　　j. The top of the slab must be brushed to remove any excess paste. 　　k. Grouting of ducts and tensioning of steel strands must not be carried out below 5°C. 　　l. The grout used for the pores should contain a slight expansion agent, with the expansion rate to be kept at no more than 10%, and specimens must be retained for strength testing. 　　The grouting strength must reach 55% of that of the beam structure, or reach grade 20#, before the beam can be moved. 　　(Prestress) n. The position of the embedded components must be accurate. 　　o. The position of the bellows must be accurate; care must be taken to prevent it from being punctured during pouring. 　　p. Pay attention to proper maintenance; lifting and stacking can only be carried out once the concrete has reached 100% of its strength. When stacking, make sure to use supports under the lifting points. 　　②Plate installation: a. The contact areas between the bottom surface of the plate and the top surface of the cap, as well as with the supports, should be tight; if necessary, a stainless steel plate should be used as an additional layer (the steel plate should be placed under the support and extend 2 cm beyond it). The steel plates must be prepared before installation; otherwise, the installation work shall not proceed. b. The designed width must be maintained at the expansion joints (if possible, the plates should be installed first before constructing the back wall). 　　③Pouring the hinge joint: a. The loose material on the joint surface must be removed. 　　b. First, fill the bottom of the hinge joint with high-strength cement mortar. 　　e. Pour the concrete only after the mortar has reached 50% of its strength, and vibrate it thoroughly to ensure compactness. 　　d. If the bottom of the slab is relatively flat, a concave joint should be used. 　　④Railings and guardrails: a. The top levels of the railing posts should be at the same elevation and lie on a straight line. 　　b. Vibration during concrete pouring at the inclined sections of the guardrail should be intensified to reduce honeycombing and pitting. 　　c. The guardrail spacers should be vertical, or within the grooves if the guardrail has such grooves. 　　d. The profile of the guardrail should be straight. 　　e. When a composite deck is used, the bottom surface of the water inlet of the drainage holes should be slightly lower than that of the cement concrete pavement. 　　⑤Cement concrete bridge deck pavement: a. The top surface of the deck should be cleaned thoroughly before pouring. 　　b. The rebar mesh should be supported by shims. 　　c. Strictly control flatness and cross-slope. 　　The elevation at end d is the same as the top of the back wall. 　　e. The top surface must not have any layer of loose paste after brushing. 　　⑥Backfilling behind the embankment: a. Layered filling with lime soil should be used, followed by compaction. 　　b. When filling in layers and compacting, the ends of the subgrade should be stepped, and the length should meet the requirements. 　　⑦The expansion joint should be smooth in transition with the bridge deck pavement. 　　⑧Asphalt concrete deck: a. The adhesive layer should be applied evenly to avoid spills, over-application, and contamination of the guardrails. 　　b. Roll compact to the edges. 　　c. Strictly control the cross slope. 　　d. The drain outlet should be smooth. 　　⑨Slope protection: a. Ensure the proper thickness. 　　b. The dirt on the surface of the blocks should be washed clean. 　　c. Build in layers, ensure proper grouting, and stagger the vertical joints. 　　d. Settlement joints must be vertical and continuous. 　　⑩Reinforcement bar processing: a. The welding length at the lap joint should be 10d+2cm for single-sided welding, and 5d+2cm for double-sided welding. b. It is necessary to ensure that the two reinforcement bars are aligned concentrically during lap welding. 　　c. The type of welding rod must meet the requirements. 　　d. During construction, contamination by oil and dirt should be prevented. 　　e. Under the rebar as well as the finished and semi-finished products, wooden pads should be placed with a thickness of no less than 15 cm, and they should be covered with tarpaulins on top. 　　(III) Auxiliary Works 　　1. Signs: 　　① The sign surfaces are clean and undamaged. 　　②The bearing capacity of the foundation must meet the requirements, the installation height (base) must be consistent, and tilting after installation is strictly prohibited. 　　2. Markings 　　① The working surface must be thoroughly cleaned ； There are no obvious burrs at the edges of the marked lines after spraying. 　　②The reflective marker glass beads should be uniform. 　　③There shall be no contamination outside the marked lines. 　　3. Level crossings 　　① The base layer should be constructed in strict accordance with the design. 　　②The transition between curbs should be smooth and curved. 　　③The asphalt surface layer should have smooth joints, with proper length and thickness, and must be fully compacted. 　　4. The warning posts must be of the same height and aligned in a straight line. 　　5. Corner stone 　　① Three straight lines, with both surfaces smooth. 　　②The foundation is compact. 　　③The break should be aligned vertically. 　　④All work related to the curbs in the same section should be completed on the same day. 　　⑤The plaster must be used in its raw form; it is not allowed to use powdered or ground material. 　　6. Shoulder 　　① The surface should be smooth and compact. 　　②The edges are straight, and the curves are smooth. 　　③There is no water-blocking phenomenon. 　　(IV) Internal documents 　　1. Test and inspection personnel shall be responsible for the accuracy of the test and inspection data. The forms in the internal documents must fully reflect all aspects of the tests; there should be no discrepancies in dates among different documents. Signatures must be provided by the relevant personnel themselves, and no one else is allowed to sign on their behalf. 　　2. The surface of the documents should be clean and tidy, with clear handwriting and uniform font. 　　3. All internal documents shall be organized using A4 paper. 　　4. The internal documentation must be compiled within 24 hours after the completion of each sub-project.