03-02 - SOW Attachment 02 - Design Submittal.pdf

SUBSURFACE CONSTRUCTORS, INC.

Job No.: 18-G073 Page: 1

Job Title: Fisher House – Togus VAMC Campus

Chelsea, Maine

Date: 8/17/18 Made by: KD Checked by: KO/WF

DESIGN SUBMITTAL 101 ANGELICA STREET, ST. LOUIS, MO 63147

INTRODUCTION

Ground improvement using vibro–concrete columns (VCC) have been proposed to accommodate the foundations for the proposed Fisher House building to be located on the Togus VAMC Campus, east of Pond Road in the City of Chelsea, Maine.

The objective of the vibro-concrete column ground improvement would be to introduce

“reinforcing” elements (i.e. concrete columns) into the soil profile to provide inclusions in the subgrade soils to enhance bearing capacity and settlement characteristics. The VCC ground improvement elements are designed as individual load carrying capacity elements.

GROUND CONDITIONS

The subsurface conditions utilized in our design included the borings and insitu/laboratory testing performed by S.W. Cole Engineering, Inc. (SWC). in their April 6, 2018 report titled Explorations and Geotechnical Engineering Services—Proposed Fisher House—Togus VAMC Campus—

Chelsea, Maine. Specifically, we adopted Borings B–101 through B–104.

The site generally consists of granular and cohesive existing fill atop peat and organic silt atop silty clay and grading to gravely sand to the maximum depth explored by the Geotechnical Engineer (29 feet). The existing fill materials consist of varying proportions ofsilt, gravely sand, and silty sand.

The existing fill generally exhibited N–values from standard penetration tests (SPT) varying between 2 to 27 blows per foot (bpf). The organic materials exhibited N–values varying between 1 through 8 bpf. The natural cohesive soil deposits generally exhibited an N–values of 1 bpf. The natural granular soil deposits generally exhibited N–values of 17 to 18 bpf. Bedrock was not encountered by the Geotechnical Engineer to their maximum explored depth.

SOIL PROPERTIES AND ELEVATONS FOR DESIGN

We understand that the site will require approximately two (2) to three (3) feet of grade–raise fill will be placed to meet the anticipated finished floor elevation for the proposed structure. We have considered the placement of this fill prior to VCC installation in our design.

The soil profile below the anticipated founding depths for the proposed structure was determined by a statistical analysis of the available subsurface data. The N–value information was tabulated for each depth in each sounding. The N–values of each layer were averaged; minimum and maximum N–values were determined for each layer; and a truncated mean (dropping the maximum and minimum values) was calculated. These numbers are included in our N–Value Calculator in

Appendix A.

For our design values, we used the lower of the average or truncated mean N–value for a given layer. The thicknesses and material types of the boring information were analyzed and averaged into layers for our design properties. Elevation adjustments for the design values were accommodated by determining elevations and depths of the foundation elements (based on our assumed working level elevation), which are shown as the founding depth shown on our calculation sheets.

Job No.: 18-G073 Page: 2

Job Title: Fisher House – Togus VAMC Campus

Chelsea, Maine

The soil parameters used in our VCC design are summarized in Table 1 below:

Table 1

Soil Unit Depth Range (feet) In-Situ

N– Value (bpf)

Proposed/Existing Fill & Organics 0-8 0

Natural Cohesive Soil 8-27 1

Natural Granular Soil 27+ 17

BEARING PRESSURE REQUIREMENTS

The ground improvement has been designed to support the following bearing pressure:

• A maximum uniformly distributed load (UDL) of up to 2,500 psf beneath the continuous wall footings.

PERFORMANCE REQUIREMENTS

In addition to safely supporting the specified foundation pressure, the ground improvement is based upon limiting post construction total settlement to a maximum of one (1 inch with a maximum differential of ½ inch. The estimated settlement does not include any settlement that may occur due to the weight of structural fill used to adjust or raise site grades.

We do request we be copied on compaction test reports and foundation observation reports to be performed by the Geotechnical Engineer.

DESIGN

The VCCs for this project will be approximately 18 inches in diameter and consist of 3,000 pounds per square inch (psi) ready mix concrete. VCCs will be installed beneath the designated areas at the frequency and spacing shown on the layout drawing.

VCC installation will commence from the working platform level (estimated at finished floor subgrade for the proposed building), with VCCs installed to an approximate depth of 27 feet or

“practical refusal.” For purposes of our design for this project, “practical refusal” will be encountered on the natural granular deposits and will vary in the field. Actual working platform level elevations and VCC depths will be determined in the field prior to installation and confirmed with design calculations. Reasonable measures will be taken to complete the installation of VCCs to a depth of 1 to 2 feet below base of footing elevations.

“Practical refusal” is defined as a vibroflot penetration rate of 6 inches per 30 seconds. The depth of “practical refusal” will be reviewed by Subsurface Constructors, Inc. (SCI) design engineers.

Refusals, if shallow, may need to be removed by excavation means and replaced with granular backfill.

Load testing will be performed on a representative VCC ground improvement element. The location of which will be mutually agreed upon in the field by representatives of SCI, our client, Job No.: 18-G073 Page: 3

Job Title: Fisher House – Togus VAMC Campus

Chelsea, Maine and any third-party inspector. See our discussion on modulus testing, attached to this submittal for further information.

DESIGN CALCULATIONS

For VCC ground improvement elements, individual pile capacities have been calculated based on the average soil conditions and VCC length below the base of footings. These results are summarized on the VCC Footing Loading Calculator Sheet, which also determines the number of columns for a particular footing size. Settlement calculations have been produced (taking account of the loading conditions described above) and based upon the soil profile and parameters discussed herein. The design calculations are provided in Appendix A. The calculations are based upon forming VCCs with a typical diameter of the order of 18 inches.

Predrilling may be required in some areas of the site due to variable compaction and rubble inclusions. SCI will determine in the field which holes can be completed using vibro methods for hole establishment, and whether complete or partial predrilling is required.

The results of the settlement calculations for each method indicate maximum post construction settlements of less than one (1) inch. We would anticipate the maximum differential settlement to be less than ½ inch.

INSTALLATION OF SERVICES AFTER VCC INSTALLATION

Where installation of services are proposed following installation of VCCs, appropriate measures need to be taken by the contractor installing the foundations and services, to ensure that the integrity of the VCC treatment is not compromised. As a general rule, any excavation which potentially intersects a line drawn down at 45 degrees at underside of foundation level will potentially impact on the integrity of the treated ground due to disturbance of the treated ground. Where this occurs, the disturbed soil should be removed and replaced with lean mix concrete until back above the 45-degree line, (dependent upon the requirements of the Local Authority).

Job No.: 18-G073 Page: 4

Job Title: Fisher House – Togus VAMC Campus

Chelsea, Maine

APPENDICES

The following documents are included in these appendices to support our submittal:

Appendix A – Design Calculations

N-Value Worksheet

27’ VCC Capacity

1.33” x 48’ Group Pile Consolidation Settlement

1.67’ x 56’ Group Pile Consolidation Settlement

Appendix B – Installation Procedure

Ground Stabilization by Vibro-Concrete Columns Process Method Statement

Appendix C – Soil Borings

SWC Exploration Location Plan

SWC Boring Logs B–101 through –104

Appendix D –Vibro Concrete Column Layout

Sheet 1 – Foundation Plan

Appendix A

Design Calculations

N‐Value Calculator Sheet Fisher House ‐ Togus VAMC Campus Chelsea, Maine

Depth B‐101 B‐102 B‐103 B‐104 Average Truncated Mean Minimum Maximum 0‐2 12 2 5 27 11.5 8.5 2 27 2‐4 5 2 11 12 7.5 8.0 2 12 4‐6 1 1 6 8 4.0 3.5 1 8 6‐8 1 1 5 4 2.8 2.5 1 5 10‐12 1 1 1 1.0 1.0 1 1 15‐17 1 0 1 0.7 1.0 0 1 17‐19 1 1.0 N/A 1 1 21‐23 17 18 17.5 N/A 17 18 W Depth Dry Dry Dry Dry N/A N/A 0 0 Elev N/A N/A N/A N/A N/A N/A 0 0

N‐values in red are interpolated from unconfined compressive strengths

Individual Vibro Concrete Column Capacity

Fisher House - Togus VAMC Campus

Chelsea, Maine

0 8 0 8 0

8 27 1 19 19 0.25 19.90 22.38 24.87 29.85 100%

27 30 17 3 0 2.1 0.00 0.00 0.00 0.00 35%

30 5

VCC Length (ft) = 24

Total Capacity (kips) = 19.90 22.38 24.87 29.85 67.50% Avg. Grout Overage

Dia. (in) Dia. (ft) Nc 9.95 11.19 12.44 14.92 Allowable Friction (kips)

16 1.33 4.19 1.40 9.00 4.97 5.60 6.22 7.46 Allowable Friction (tons)

18 1.50 4.71 1.77 9.00 14.24 18.02 22.25 32.04 Allowable End Bearing (kips)

20 1.67 5.24 2.18 9.00 7.12 9.01 11.13 16.02 Allowable End Bearing (tons)

24 2.00 6.28 3.14 9.00 24.19 29.22 34.69 46.97 Allowable Pile Capacity Compression (kips)

12.10 14.61 17.34 23.48 Allowable Pile Capacity Compression (tons)

Column Material Properties 301.6 381.7 471.2 678.6 Allowable Column Capacity-Grout Strength (kips)

Concrete f'c (psi) = 3000 150.8 190.9 235.6 339.3 Allowable Column Capacity-Grout Strength (tons)

FS = 2

End Bearing Properties

Material Type = 2 (1 for Cohesive, 2 for Granular)

N-Value = 17 (30 or Less for Type 1, 50 or Less for Type 2)

Cohesion = N/A ksf

Outer

Surface

Area (sf) End Area (sf) overtake

18" Diameter

Capacity (kips)

Starting

Depth (ft)

End

Depth (ft)

N-value

(bpf) Interval (ft) Shear (ksf)

16" Diameter

Capacity (kips)

24" Diameter

Capacity (kips)

Interval

Override (ft)

20" Diameter

Capacity (kips)

VCC Footing Loading Calculator Sheet

Chelsea, Maine

Location

Footing Width

(B), ft

Footing Length

(L), ft Area (BxL), ft^2

Footing Load, psf

Number of

Columns

Column Length, ft

Load Per

Column, kips

Allowable

Capacity, kips FS Notes

16" Wide 1.33 48 64.00 2500 6 27 26.7 29.2 2.2 24" VCC, 8' Spacing

20" Wide 1.67 56 93.33 2500 8 27 29.2 29.2 2.0 24" VCC, 7' Spacing

VCC Length Table

27 24.2 29.2 34.7 47.0

16" Total

Capacity, kips

18" Total

Capacity, kipsLength, ft

20" Total

Capacity, kips

24" Total

Capacity, kips

Single Layer Clay Predicted Consolidation Settlement Calculator Sheet for Group Piles

Chelsea, Maine

2:1 Approximation for Delta Sigma L = 27 ft (Length of piles)

2 ft (Width of pile group) 50 ft (Length of pile group)

1.33 ft (Width of pile cap) 48 ft (Length of pile cap)

2/3L = 18 ft (2/3 height of pile length) 27 ft (Depth to incompressible layer)

2500 psf (Bearing pressure of pile group) 159600 lb (Load on pile group)

4.5 ft (Depth to midpoint below 2/3L)

450.52929 psf (Increase in stress at midpoint Zi)

Where:

Equation 11.131 from Das (2007) From Das (2007)

Consolidation Settlement Calculator of Clay Using Consolidation Test

0.63 (Compression index) For Normally Consolidated Soils

0.126 (Recompression index)

0.7 (Initial void ratio)

5000 psf (Preconsolidation stress)

H = 9 ft (Thickness of compressible layer) Equation 17.17 from Coduto (1999) 27 ft (Depth to water) For Case I Overconsolidated Soils

120 pcf (Unit weight of soil)

57.6 pcf (Effective unit weight of soil)

4536 psf (Initial vertical effective stress)

4986.5293 psf (Final vertical effective stress) Equation 17.18 from Coduto (1999)

For Case II Overconsolidated Soils δ= 0.28 in (Total consolidation settlement)

Equation 17.19 from Coduto (1999) 𝛿 = 0.85𝐻 𝐶𝑐

1 + 𝑒0 log 𝜎′𝑧𝑓 𝜎′𝑧𝑜

(𝜎′𝑧𝑜≈ 𝜎′𝑐) ∶ 𝛿 = 0.85𝐻 𝐶𝑟

1 + 𝑒0 log 𝜎′𝑧𝑓 𝜎′𝑧𝑜

(𝜎′𝑧𝑜< 𝜎′𝑧𝑓 ≤ 𝜎′𝑐) ∶ 𝛿 = 0.85𝐻 𝐶𝑟

1 + 𝑒0 log 𝜎′𝑐 𝜎′𝑧𝑜

𝐶𝑐

1 + 𝑒0 log 𝜎′𝑧𝑓 𝜎′𝑐

(𝜎′𝑧𝑜< 𝜎′𝑐 < 𝜎′𝑧𝑓) ∶

∆𝝈′𝒊 = 𝜎′𝑧𝑜 = 𝜎′𝑧𝑓 = 𝜎′𝑐 = 𝑒𝑜 = 𝐶𝑟 = 𝐶𝑐 = 𝛾′ = 𝛾 = 𝐷𝑤 = 𝑧𝑖 =

𝐿𝑔 = 𝐵𝑔 =

𝐷𝐼𝐿 =

𝑄𝑔 =

∆𝜎′𝑖 = 𝑄𝑔

(𝐵𝑔 + 𝑧𝑖)(𝐿𝑔 + 𝑧𝑖) 𝑞𝑔 =

𝐿𝑐 = 𝐵𝑐 =

Clay Consolidation Calculator from LL Assumptions from Skempton (1954) Cc = 0.009 (LL - 10) Cs = 1/5 Cc Cs = Cr

Avg. LL = 80 (Average Liquid Limit) Cc = 0.63 (Compression index) Cs = 0.126 (Recompression index)

Single Layer Clay Predicted Consolidation Settlement Calculator Sheet for Group Piles

Chelsea, Maine

2:1 Approximation for Delta Sigma L = 27 ft (Length of piles)

2 ft (Width of pile group) 8 ft (Length of pile group)

1.67 ft (Width of pile cap) 56 ft (Length of pile cap)

2/3L = 18 ft (2/3 height of pile length) 27 ft (Depth to incompressible layer)

2500 psf (Bearing pressure of pile group) 233800 lb (Load on pile group)

4.5 ft (Depth to midpoint below 2/3L)

2877.5385 psf (Increase in stress at midpoint Zi)

Where:

Equation 11.131 from Das (2007) From Das (2007)

Consolidation Settlement Calculator of Clay Using Consolidation Test

0.63 (Compression index) For Normally Consolidated Soils

0.126 (Recompression index)

0.7 (Initial void ratio)

5000 psf (Preconsolidation stress)

H = 9 ft (Thickness of compressible layer) Equation 17.17 from Coduto (1999) 27 ft (Depth to water) For Case I Overconsolidated Soils

120 pcf (Unit weight of soil)

57.6 pcf (Effective unit weight of soil)

4536 psf (Initial vertical effective stress)

7413.5385 psf (Final vertical effective stress) Equation 17.18 from Coduto (1999)

For Case II Overconsolidated Soils δ= 0.68 in (Total consolidation settlement)

Equation 17.19 from Coduto (1999) 𝛿 = 0.85𝐻 𝐶𝑐

1 + 𝑒0 log 𝜎′𝑧𝑓 𝜎′𝑧𝑜

(𝜎′𝑧𝑜≈ 𝜎′𝑐) ∶ 𝛿 = 0.85𝐻 𝐶𝑟

1 + 𝑒0 log 𝜎′𝑧𝑓 𝜎′𝑧𝑜

(𝜎′𝑧𝑜< 𝜎′𝑧𝑓 ≤ 𝜎′𝑐) ∶ 𝛿 = 0.85𝐻 𝐶𝑟

1 + 𝑒0 log 𝜎′𝑐 𝜎′𝑧𝑜

𝐶𝑐

1 + 𝑒0 log 𝜎′𝑧𝑓 𝜎′𝑐

(𝜎′𝑧𝑜< 𝜎′𝑐 < 𝜎′𝑧𝑓) ∶

∆𝝈′𝒊 = 𝜎′𝑧𝑜 = 𝜎′𝑧𝑓 = 𝜎′𝑐 = 𝑒𝑜 = 𝐶𝑟 = 𝐶𝑐 = 𝛾′ = 𝛾 = 𝐷𝑤 = 𝑧𝑖 =

𝐿𝑔 = 𝐵𝑔 =

𝐷𝐼𝐿 =

𝑄𝑔 =

∆𝜎′𝑖 = 𝑄𝑔

(𝐵𝑔 + 𝑧𝑖)(𝐿𝑔 + 𝑧𝑖) 𝑞𝑔 =

𝐿𝑐 = 𝐵𝑐 =

Appendix B

Installation Procedure

GROUND STABILIZATION BY VIBRO CONCRETE COLUMNS (VCC)

PROCESS

METHOD STATEMENT

PLANT & EQUIPMENT

The technique involves the use of a vibroflot, comprising a hydraulic powered eccentric weight assembly enclosed in heavy tubular steel casing. The vibroflot is suspended from a crawler crane.

The basic length of the vibroflot assembly is 26.25 feet (8 m) although extension tubes may be added to increase the vibroflot length as the depth of treatment dictates. The vibrator diameter is 1 foot (310 mm) and is powered by a 130 kw portable diesel power pack and thus generates high centrifugal forces in the horizontal plane at a frequency of 50 cycles per second in most cases. The nose of the vibroflot is tapered to aid in penetration of the ground while vertical fins prevent the vibroflot from rotating during penetration. Attached to the vibroflot is a tube of 7⅞ inches (200

mm) diameter, where a grout pump is attached. If predrilling is required, it will be accomplished using a Watson 300 or equivalent drill rig.

VIBRO CONCRETE COLUMNS TECHNIQUE

This is a completely dry technique and the cycle of operations is described as follows. The vibroflot and grout connector hose suspended from the crane, are lowered to the ground and penetrate quickly through the weak soils. Where stiff or dense soils or rubble fill materials are encountered, the hole may be predrilled through these layers. After reaching the required depth, grout or concrete is pumped through the auxiliary tube to the bottom of the hole to the tip of the vibroflot during initial withdrawal. The vibroflot then repenetrates the concrete or grout, displacing it into the surrounding soil to form an enlarged base, with increased bearing capacity.

The vibroflot is then slowly withdrawn as concrete or grout is pumped at maintained pressure to form a continuous shaft of concrete or grout to the desired bearing elevation. Often, a slight mushrooming of the vibro concrete column is present to assist in load transfer.

In granular soils, the effect of the vibrations is to produce a marked improvement in the relative density of the surrounding material thus significantly improving the allowable bearing capacity and settlement characteristics. In cohesive soils, little improvement occurs in the engineering properties of the clay soils between concrete columns and the improvement of the formation is achieved by the combined effect of the weak soils and the stiff concrete columns.

VIBRO CONCRETE COLUMNS

Vibro concrete columns are constructed to effect stabilization of the treated ground and offer the load carrying characteristics of deep foundations. Typically, vibro concrete column diameters are of the order of 1.33 to 2.0 feet. The column diameter will naturally vary with the technique and soils condition, but generally the weaker the soils, the larger the diameter of concrete column.

The vibro concrete columns are normally constructed directly beneath the main foundations, usually in single or multiple rows beneath strip foundations and in groups beneath pad foundations. Area or floor slab treatment is normally carried out in grid spacing. The spacing and arrangements of the concrete columns are dependent on the soils conditions and the loads carried by the foundations.

Appendix C

Soil Borings

Appendix D

Vibro Concrete Column Layout