Principles for foundation pit retaining scheme review: the retaining structure system should conform to actual engineering conditions, with reasonable type selection, correct calculations, technical feasibility, economical selection, complete content, detailed drawings, and strong operability.

The review mainly includes four parts: preliminary review, textual description, calculation report, and construction drawings.

Let's take a look at what the review key points are~

The review materials for the foundation pit design scheme should include: the foundation pit retaining design scheme (including three parts: textual description, calculation report, and construction drawings, with electronic versions provided), the qualification certificate and business license of the foundation pit retaining design unit, copies of the registration certificates of design personnel, surrounding municipal pipeline drawings, basement structure construction drawings, engineering geological survey reports, etc.

The specific review requirements are as follows:

I. Preliminary Review Content

1. Whether the retaining design unit has the corresponding qualifications, and whether the design personnel have geotechnical engineering registration seals;

2. Whether the design basis complies with the requirements of national, industry, and local policies, laws, and regulations.

II. Completeness of Content

The content of the foundation pit retaining design scheme should include three parts: textual description, calculation report, and construction drawings.

Textual Description

1. Main content of the textual description

Compilation basis, project overview, analysis of surrounding environmental conditions, analysis of engineering geological conditions, analysis of key and difficult points, selection of retaining type, technical requirements for the retaining system, requirements for foundation pit excavation and construction, on-site monitoring and emergency measures.

2. Review key points of project overview

a) Project scale, land red line range, construction entities of all parties, building structure overview. In particular, the basement structure design situation, including the distribution of surrounding pile caps, ground beams, elevator shafts, fire water tanks, sumps, car ramps, post-cast strips, and the form of engineering piles, etc.;

b) Whether the determination of foundation pit excavation depth is reasonable. For soft clay, relatively dense pile cap distribution, and basements with ground beams, the pile cap cushion layer should preferably be taken as the foundation pit excavation depth; in other cases, comprehensive consideration may be given; for pits within pits near the foundation pit edge or locally deeper areas, the excavation depth should be comprehensively considered;

c) Whether the determination of the foundation pit safety grade is reasonable.

3. Review key points of surrounding environment

a) The distance of surrounding buildings and structures, foundation form, structural form, construction age, description of existing conditions, and analysis of the degree of impact on the foundation pit;

b) The distance of surrounding roads; pipe type, pipe diameter, distance, buried depth, etc. of pipelines; river distribution, slope state or integrity and possible impact on the foundation pit, description of natural ground elevation, etc., and analysis of the degree of impact on the foundation pit;

c) Analysis of the impact of foundation pit excavation on key buildings, structures, and pipelines.‍

4. Review key points of geological conditions

a) The geological report provided by a professional unit should be combined to review whether the provided soil physical and mechanical parameters (unit weight, shear strength indicators, permeability coefficient, compression modulus, water content, void ratio, etc.) are complete, and to review whether the values of relevant physical and mechanical parameters are correct and reasonable;

b) Special attention should be paid to whether adverse geological conditions exist, such as confined water, flowing sand, biogas, hidden ponds, muddy soil or weak interlayers, faults, karst (caves), rivers, etc., and whether the foundation pit design has considered the impact of adverse geological conditions on foundation pit safety;

c) Whether the provided exploration point and line plan layout drawings and engineering geological profile drawings are complete.‍

5. Review key points of the rationality of retaining design type selection

a) Whether the retaining type comprehensively considers the engineering structure, surrounding environment, engineering geology, project construction period, and feasibility, and whether it is safe, reasonable, and economical;

b) Whether the comparison and determination of schemes are reasonable;

c) Whether the foundation pit retaining exceeds the red line;

d) Whether the number of levels, form, and spacing of the planar support system are reasonable;

e) Whether dewatering and drainage conditions are comprehensively considered in combination with geological conditions, surrounding environment, retaining body type, etc., with focus on whether dewatering is feasible, the possible impact of dewatering on the surrounding environment, whether the calculation report matches the dewatering control standards, the treatment method for confined water, dewatering method and structure, and the number and time of well sealing;

f) Whether the overall construction sequence and construction feasibility have been considered;

g) Whether the control values of foundation pit deformation are reasonable, and whether the impact of deformation on the surrounding environment is reasonable and controllable;

h) Whether the countermeasures adopted for the difficult and key points of the surrounding environment, engineering geology, and building structure are reasonable.‍

6. Review key points of technical requirements for the retaining system

a) Whether the construction sequence is reasonable, whether it covers all construction processes, and whether the technical parameters are comprehensive, reasonable, and accurate;

b) Whether the construction conditions are comprehensive and reasonable, and whether they have clear guiding significance for construction;

c) Whether the quality inspection standards for the retaining body are clearly proposed, whether the inspection standards are reasonable and comply with code requirements, and whether the inspection standards are consistent with the design calculation parameters.‍

7. Review key points of foundation pit excavation and construction requirements

a) Whether foundation pit excavation and construction requirements are proposed in combination with the retaining design situation, construction site conditions, road traffic conditions, sales requirements, construction schedule plan requirements, etc.;

b) Whether foundation pit excavation and construction requirements are proposed in combination with site geological conditions (especially soft clay layers with high water content), the distribution of structural post-cast strips, and engineering pile protection requirements (especially prestressed pipe piles), etc.;

c) Whether the parameters for layered and segmented earthwork excavation are reasonable; whether excavation requirements for car ramps and pits within pits are proposed;

d) Whether targeted excavation measures have been taken in combination with the difficult and key points of the surrounding environment, engineering geology, and building structure;

e) Whether the load limit requirements around the foundation pit are clearly defined;

f) Other targeted issues.‍

8. Review requirements for on-site monitoring and emergency plans

a) Whether the monitoring plan layout is reasonable;

b) Whether the monitoring content, quantity, frequency, and warning values comply with the requirements of the "Technical Code for Monitoring of Building Foundation Pit Engineering" GB50497—2009 and the actual engineering situation;

c) Whether the layout of monitoring points is representative;

d) Whether the monitoring requirements for surrounding buildings, structures, underground pipelines, etc. meet safety requirements;

e) Whether the emergency plan is comprehensive, and whether corresponding targeted measures have been proposed for various adverse situations and safety hazards that may occur during foundation pit excavation.‍

Calculation Report

a) Whether the load values are reasonable, and whether deep new fill soil has been considered as surcharge;

b) Whether the values of soil mechanical parameters are reasonable, and whether the most unfavorable state of soil layer distribution has been considered;

c) Whether the input parameters are incorrect;

d) Whether the calculation sections are complete, whether the hole positions are correctly selected, and whether the soil layers are shown on the section drawings;

e) Whether the calculation process is correct, whether the calculation content is complete, and whether the calculation depth is consistent with the drawings;

f) Whether the calculated works are consistent with the drawings and construction requirements;

g) Whether the calculation results meet code requirements.‍

Construction Drawings

a) Whether the drawings are complete, whether the expression is clear, and whether there are contradictions;

b) Whether the plan layout is reasonable, and whether the support layout is reasonable;

c) Whether the surrounding environment drawing is clear and explicit;

d) Whether the section selection is representative, and whether it has been comprehensively determined by considering factors such as changes in geological profiles, changes in excavation depth, layout forms of building structures, and surrounding environmental conditions;

e) Whether the sections and nodes are clear and accurate, and whether they are consistent with the calculation report;

f) Whether the foundation pit dewatering and drainage layout is reasonable, whether the depth is appropriate, and whether the structure is scientific;

g) Whether the setting of the water-stop curtain is reasonable;

h) Whether the structural support replacement is reasonable;

i) Whether the monitoring plan layout is reasonable, whether the monitoring content, quantity, frequency, and warning values comply with the code and the actual engineering situation, whether the layout of monitoring points is representative, and whether the monitoring requirements for surrounding buildings, structures, underground pipelines, etc. meet safety requirements;

j) Whether the general description content of the drawings is complete and detailed; whether the compilation basis is comprehensive and correct, and whether technical requirements for the retaining system, technical requirements for key and difficult points, dewatering and drainage requirements, foundation pit excavation and construction requirements, foundation pit monitoring requirements, and emergency measures are proposed.‍