Specs - Shaft Excavation

TECHNICAL SPECIFICATIONS WW-483RR DIVISION 02: SITE WORK 02444: SHAFT EXCAVATION

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PART 1 - GENERAL

1.1 DESCRIPTION

A. The work specified in this section specifies the requirements for excavating, sheeting, and shoring required to construct pipe ramming and receiving shafts.

B. Related work specified elsewhere:

1. Section 02431, Cellular Grout Backfill.

2. Section 02446, Pilot Tube Guidance.

3. Section 02447, Casing Installed by Pipe Ramming.

4. Section 02448, Geotechnical Instrumentation and Monitoring for Pipe Ramming.

5. Section 14000, Steel Casing.

C. Definitions:

1. Refer to Section 02447.

1.2 DESIGN REQUIREMENTS

A. Design shafts to accommodate selected means and methods for performing the Work and construction of permanent structures as shown on the Plans.

B. Design shafts to conform to right-of-way limitations as shown on the Plans.

C. Design temporary shoring system to provide a minimum factor of safety of 2.0 against sliding and 1.5 against bottom heave.

D. Design temporary shoring system to incorporate pipe ramming method as specified in Section 02447 and pilot tube installation as specified in Section 02446.

E. Construct the shaft in-the-wet without the use of dewatering or sump pumping to control groundwater inflow or lower the groundwater level.

F. Construct the shaft using water-tight construction methods that limit water inflow from all sources to less than 5 gallons per minute.

G. Create and implement a plan for field verification of the shaft design that at a minimum measures and records settlement, bottom heave, groundwater elevation, and shaft member deflections weekly.

H. Design and construct jacking shafts that incorporate the maximum allowable jacking force of the pipe jacking system.

Comment [DCC1]: 02155 ground improvement not included. Ground improvement should be required to reduce inflows if inflows exceed minimum allowed in F below GI ADDED TO RELATED WORK – TITLES CHANGED ACCORDINGLY AND SORTED NUMERICALLY


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I. Utilize excavation support systems compatible with the geologic conditions identified in the Geotechnical Data Report.

J. Shoring, except for the top 5.0 feet and internal bracing members, is to remain in-place following construction.

1.3 SUBMITTALS

A. General: Submit in accordance with Section 01300.

B. Submit name and qualifications of individual designing excavation support system.

C. Submit signed and stamped drawings and calculations for the excavation support systems and for the shaft penetrations.

D. Submit dimensional site plan at each shaft location indicating utilities, structures, and public facilities that are to be protected in place.

E. Submit dimensioned site plan at each shaft indicating the location, excavation dimensions, site grading, and site development details for the excavation and work areas, and the proposed limits of disturbance. Include details of types, amounts, and positioning of materials and equipment required at each location. Show overhead and subsurface utilities and other conflicts.

F. Submit dimensioned and scaled working drawings showing excavation support systems relative to the permanent facilities. Include foundation details for all permanent structures.

G. Submit shaft monitoring information as specified herein on the same date as taken followed by the Contractor’s interpretation by noon the following work day.

H. Submit drawings showing sequence for backfilling shaft and removing shoring.

1.4 QUALITY ASSURANCE

A. Legal Standards

1. 29 CFR Part 1926 – Occupational Safety and Health Administration (OSHA) Regulations and Standards for Underground Construction

B. American Society for Testing and Materials:

1. ASTM A36 – Specification for Structural Steel

C. Qualifications:

1. Engineer: Excavation support systems shall be designed by a Civil or Structural engineer registered in the State of California who has a minimum of five years experience in shaft designs including shafts of similar size and in similar ground conditions as measured by soil type, SPT N-Values, and depth of groundwater.


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2. Surveyor: Surveying requirements same as specified in Section 02447.

3. Initial Survey: Prior to beginning demolition or excavation, the Contractor shall perform a survey that identifies and locates facilities within 50 feet of the excavation.

4. Field reporting forms shall show historical readings and be in a format acceptable to the Owner.

D. Acceptance Criteria: (NOT USED)

E. Preconstruction Meeting:

1. Hold a meeting, a minimum of two weeks prior to beginning the work specified herein.

2. Review and discuss the following items:

a. Scope of work to be performed.

b. Construction methods and constraints overview.

c. Equipment operating parameters.

d. Safety procedures.

e. Quality Control procedures and Quality Assurance requirements.

f. Reporting requirements.

g. Other issues as may be raised by either party.

F. Training: (NOT USED)

G. Testing: (NOT USED)

1.5 JOB CONDITIONS

A. Subsurface Information: Refer to the GDR.

1.6 SAFETY

A. Same as specified in Section 02447.

1.7 SEQUENCING AND SCHEDULING

A. Each shaft is to be shown on a schedule.

Comment [DCC2]: Provide location COMMENT ADDED TO HAVE PUC ADD REFERENCE LOCATION FOR GDR IN O2447


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B. Launch and receiving shaft for each drive shall be completed before commencing tunnel construction.

1.8 PRODUCT DELIVERY, STORAGE AND HANDLING (NOT USED)

1.9 WARRANTY (NOT USED)

PART 2 - PRODUCTS

2.1 MATERIALS

A. Provide all shoring materials in accordance with approved submittals.

B. Structural steel shall conform to ASTM A36.

C. Corrugated Metal Pipe (CMP) shall be zinc coated

2.2 EQUIPMENT (NOT USED)

2.3 SOURCE QUALITY CONTROL (NOT USED)

PART 3 - EXECUTION

3.1 GENERAL

A. Proposed shafts at locations other than where shown on the drawings shall comply with the following conditions:

1. Alternate, rescue, or additional shaft locations shall be defined as alternate shaft locations proposed by the CONTRACTOR.

2. All alternate shaft locations shall be acceptable to the Owner.

3. The Contractor shall obtain and provide all approvals and permits for alternate shaft locations to the Owner.

B. Protect existing structures, utilities, and public and private facilities before commencing shaft excavation.

C. Install instrumentation as shown on the Plans and as specified in Section 02448 before commencing shaft excavation.

D. Install excavation support systems in accordance with approved submittals. If settlement, support deflection, or shaft bottom movement indicate the support system requires modification, the Contractor’s engineer shall redesign and resubmit revised working drawings and design calculations.

E. Provide shaft excavations with a sump to pump out incidental, construction, and storm water.

Comment [DCC3]: Renumber and add A as “perform all work in conformance with approved submittals.” ADDED TO THIS AND ALL OTHER SPECS

Comment [DCC4]: Suggest a drawing showing areas where rescue shafts will not be acceptable. PUC WOULD HAVE TO PREPARE AS WE DON'T HAVE KNOWLEDGE OF WHERE RESCUE SHAFTS CAN AND CAN'T GO.

Comment [DCC5]: This should be the greater of within the drive or within 50 feet of the shaft locations LANGUAGE CHANGED TO REFLECT INSTRUMENTS WITHIN DRIVE AND THOSE WITHIN 50 FEET OF SHAFT.


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F. Construct pipe ramming shafts with the shoring flush with the existing ground.

G. Alternate Shaft Locations: Vertical shaft boring with a CMP liner shall be an acceptable construction method where traffic control permits.

3.2 PREPARATION (NOT USED)

3.3 SHAFT CONSTRUCTION: INTERNAL BRACING SUPPORT SYSTEM

A. Construct the internal bracing support system using whalers, struts, and/or shores as required by the design.

B. Install and maintain all bracing support members in intimate contact with other support members and with the ground.

C. Preload bracing members by jacking struts to 50 percent of the design load if necessary to control shoring movement.

D. Preload bracing members in accordance with methods, procedures, and sequence as described in the approved submittals.

E. Use procedures that produce uniform loading of bracing members without eccentricities or over-stressing and distortion of members of system.

3.4 SHAFT CONSTRUCTION: METHODS

A. Corrugated Metal Pipe (CMP) in Drilled Shaft

1. Drill the hole within the design tolerances submitted for vertical alignment, diameter, and depth. Drilled hole shall be of sufficient size to allow placing of CMP and backfilling the annular space without damaging the CMP.

2. CMP shall be true and round within design tolerances and of sufficient length to line entire hole. Install the CMP within design tolerances stipulated in the approved submittal.

3. Backfill the annular space with grout of sufficient strength and flowability to provide intimate contact with the ground and CMP. Backfill grout shall be in accordance with the approved submittals.

4. Design and construct the shaft bottom as an integral part of the entire shaft.

5. Construct the shaft in the wet. Site dewatering shall not be allowed.

6. Remove the uppermost 5 feet of the CMP shaft.

B. Interlocking Sheet Piles


Comment [DCC6]: Confirm that the plating is over the pavement and not recessed PUC HAS NOT INDICATED TO US THAT PLATING HAS TO FLUSH WITH GROUND – ALL ALONG THEY'VE INDICATED THAT PLATING COULD BE PLACED OVER THE SHORING.

Comment [DCC7]: Ensure the strength is compatible with construction method or that the construction sequence addresses grout removal STRENGTH NOT REALLY A REQUIREMENT AS GROUT IS ONLY FILLING ANNULAR SPACE THE ONLY THING THAT WOULD BE REMOVED WOULD BE THE UPPER 5 FEET OF SUPPORT SYSTEM AND THE GROUT IS LIKELY TO 'COME ALONG FOR THE RIDE' WHEN THE CMP IS REMOVED.

Comment [DCC8]: Add to section 1.2. then does not need to be restated here. DONE

Comment [DCC9]: Restates 1.2.E. this is not restated in the following two construction methods. DELETED HERE TO AVOID RESTATING

Comment [DCC10]: Add if groundwater inflow exceeds maximum allowed perform grouting until inflows are below maximum allowable. Repeat for each construction method. ADDED GROUNDWATER INFLOW LANGUAGE AND DRILLED THROUGH THE OTHER SHAFT METHODS

Comment [DCC11]: Restates 1.2.J. DELETED HERE – 1.2.J WORDED TO HAVE UPPER 5 FEET OF SHAFT SYSTEM REMOVED.



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2. Remove the uppermost five feet of the steel subsurface support system including all interior bracing.

C. Secant Piles, Slurry Walls, Cutter Soil Mixing Walls


2. Remove the uppermost five feet of any cementitious-type retaining structure.

3.5 MAINTENANCE AND REPAIR/RESTORATION (NOT USED)

3.6 INSTRUMENTATION AND MONITORING

A. Monitor shaft wall system and instrumentation in accordance with the approved shaft submittal.

3.7 FIELD QUALITY CONTROL

A. Provide quality control, testing, and inspection as required in the approved shaft design submittals.

3.8 REMOVAL OF SUPPORT SYSTEM

A. Remove excavation support in accordance with approved submittals during shaft backfill operations. Perform removal in a manner that avoids ground settlement and damage to the pipeline and adjacent facilities.

END OF SECTION

Comment [DCC13]: Restates 1.2.J. DELETED


Comment [DCC15]: Restates 1.2.J. DELETED

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Specs - Shaft Excavation