1801.2 Add section as follows:
1801.2 Foundation Types Not Covered by the Code. Types of foundations not specifically covered by the provisions of 780 CMR 18.00, and ground modification treatments to improve soils with inadequate load bearing capacity or settlement characteristics, may be permitted subject to approval by the building official. A report shall be submitted to the building official that identifies the foundation as a type not covered by existing code provisions, and contains sufficient data and analyses to substantiate the adequacy of the proposed foundation. The report shall be prepared by a registered design professional knowledgeable in the design of the proposed type of foundation or ground modification. The building official may require that an independent peer review be performed to evaluate the adequacy of the proposed design1803.1 Revise section as follows:
1803.1 General. Geotechnical investigations shall be conducted in accordance with Section 1803.2 and reported in accordance with Section 1803.6. Where required by the building official or where geotechnical such investigations involve in-situ testing, laboratory testing or engineering calculations, such investigations shall be conducted by a registered design professional.1803.2 Revise section as follows:
1803.2Investigations Required. Geotechnical investigations shall be conducted in accordance with sections 1803.3 through 1803.5. EXCEPTIONS: The building official shall be permitted to waive the requirement for a geotechnical investigation:
1. Where satisfactory data from adjacent areas is available that demonstrates an investigation is not necessary to meet the requirements of 780 CMR 18.00;2. For unoccupied structures that do not pose a significant risk to public safety in the event of failure; or3. For structures used for agricultural purposes.1803.5.4 Delete the exception
1803.5.11 In two locations replace “C” with “B, C.”
1803.5.12 In two locations replace “D” with “B, C, D."
1803.6 Add item 11 as follows:
11. Magnitude and distribution of lateral soil and ground water pressures, including seismic loads, on foundation and retaining walls.1805.4.2 Revise section as follows:
1805.42Foundation drain. A drain shall be placed around the perimeter of a foundation that consists of gravel or crushed stone containing not more than 10- percent material that passes through a No. 4 (4.75 mm) sieve. The drain shall extend a minimum of not less than 12 inches (305 mm) beyond the outside edge of the footing. The thickness shall be such that the bottom of the drain is not higher than the bottom of the base under the floor, and that the top of the drain is not less than 6 inches (152 mm) above the top of the footing. The top of the drain shall be covered with an approved filter membrane material. Where a drain tile or perforated pipe is used, the invert of the pipe or tile shall not be higher than the floor elevation. The top of joints or the top of perforations shall be protected with an approved filter membrane material. The pipe or tile shall be placed on not less than 2 inches (51 mm) of gravel or crushed stone complying with Section1805.4.1, and shall be covered with not less than 6 inches (152 mm) of the same material.1805.4.2 Add exception as follows
EXCEPTION: The foundation drain may be omitted if determined not to be necessary by a registered design professional.1805.5 Add section as follows:
1805.5Impacts on Groundwater Levels. Below-grade structures, their appurtenances and foundation drains shall be designed and constructed so as not to cause changes to the temporary or permanent groundwater level if such changes could adversely impact nearby structures or facilities including deterioration of timber piles, settlement, flooding or other impacts. 1806.2 Replace the text "Table 1806.2" with "Table 1806.2 or Table 1806.2a," and add Table 1806.2a as follows: 1086.2aTABLE 1806.2a PRESUMPTIVE ALLOWABLE VERTICAL BEARING PRESSURESMaterial Class | Description | Notes | Consistency in Place | Net Bearing Pressure (tons/ft2)1,2,3 |
1a | Massive bedrock: Granite, diorite, gabbro, basalt, gneiss | 4 | Hard, sound rock, minor jointing | 100 |
1b | Quartzite, well-cemented conglomerate | 4 | Hard, sound rock moderate jointing | 60 |
2 | Foliated bedrock: slate, schist | 4 | Medium hard rock, minor jointing | 40 |
3 | Sedimentary bedrock: cementation shale, siltstone, sandstone, limestone, dolomite, conglomerate | 4 | Soft rock, moderate jointing | 20 |
4 | Weakly-cemented sedimentary bedrock: compaction shale or other similar rock in sound condition | 4 | Very soft rock | 10 |
5 | Weathered bedrock: any of the above except shale. | 5 | Very soft rock, weathered and/or major jointing and fracturing | 8 |
6 | Slightly-cemented sand and/or gravel, glacial till (basal or lodgement), hardpan | 6 | Very dense | 10 |
7 | Gravel, widely-graded sand and gravel; and granular ablation till | 6 | Very dense Dense Medium dense Loose Very loose | 8 6 4 2 NOTE 9 |
8 | Sands and non-plastic silty sands with little or no gravel (except for Class 9 materials) | 6, 7 | Dense Medium dense Loose Very loose | 4 3 1 NOTE 9 |
9 | Fine sand, silty fine sand, and non-plastic inorganic silt | 6, 7 | Dense Medium dense Loose Very loose | 3 2 1 NOTE 9 |
10 | Inorganic sandy or silty clay, clayey sand, clayey silt, clay, or varved clay; low to high plasticity | 8 | Hard Stiff Medium Soft | 4 2 1 NOTE 9 |
11 | Organic soils: peat, organic silt, organic clay | 8,9 | | NOTE 9 |
1. Net bearing pressure shall consist of the bearing pressure applied at the bottom of the foundation, including the weight of the foundation and any soil immediately overlying the foundation, minus the pressure calculated for a height of soil extending from the bottom of the foundation to the lowest ground surface level immediately adjacent to the foundation.2. Where the load-bearing layer directly below the foundation is underlain by a weaker layer, the bearing pressure on the weaker layer shall be checked by assuming that the load is spread uniformly at an angle of 30º with the vertical, or by using another suitable method to determine the bearing pressure on the weaker layer.3. The bearing strata shall be adequately protected against disturbance. If the bearing materials are disturbed from any cause, for example, by flow of water, freezing or construction activities, the extent of the disturbance shall be evaluated by a registered design professional to determine appropriate remedial measures or reduced allowable bearing pressures.4. The allowable bearing pressures may be increased by an amount equal to ten percent for each foot of depth below the surface of sound rock; however, the increase shall not exceed two times the value given in the table.5. Weathered shale and/or weathered compaction shale shall be included in Material Class 10. Other highly weathered rocks and/or residual soils shall be treated as soil under the appropriate description in Material Classes 6 to 10. Where the transition between residual soil and bedrock is gradual, a registered design professional shall make a judgment as to the appropriate bearing pressure.6. Allowable bearing pressures may be increased by an amount equal to five percent for each foot of depth of the bearing area below the minimum required in section 1806.0; however, the bearing pressure shall not exceed two times the value given in the table. For foundation bearing areas having a least lateral dimension smaller than three feet, the allowable bearing pressure shall be 1/3 of the tabulated value times the least dimension in feet.7. Evaluate susceptibility to liquefaction in accordance with section 1806.4.8. Evaluate long-term settlement due to consolidation for these materials.9. A registered design professional shall be engaged to provide recommendations for these special cases.1806.3 Revise section as follows:
1806.3Lateral Load.Where foundations are required to resist lateral loads, the allowable values of sliding friction, adhesion and passive pressure for design shall be determined by a registered design professional.1806.3.1 through 1806.3.4 Delete subsections and replace with subsection 1806.3.1 as follows:
1806.3.1Increase for Poles. Isolated poles for uses such as flagpoles or signs and poles used to support buildings that are not adversely affected by a 1/2-inch (12.7 mm) motion at the ground surface due to short-term lateral loads shall be permitted to be designed using lateral bearing pressures equal to two times the tabular values of Table 1806.2.1806.4 Add sections 1806.4 through 1806.4.4 as follows:
1806.4.Liquefaction.The potential for liquefaction induced by the design earthquake in saturated clean to silty sands and non-plastic silts (Soil Classes 8 and 9 in Table 1806.2a) shall be evaluated as indicated in sections 1806.4.1 through 1806.4.4.1806.4..1 Standard Penetration Test. For cases with a generally flat ground surface, the susceptibility to liquefaction may be evaluated using Figure 1806.4 on the basis of Standard Penetration Test (“SPT”) blow counts, N (blows per foot) values that have been corrected for hammer efficiency to be SPT N60 (blows per foot) values. N60-values are intended to be used with Figure 1806.4 and SPT N-values measured in the field should only be corrected for hammer energy. Hammer type shall be as described in ASTM Standard Method D6066. If the type of hammer is not known, Figure 1806.4 may be used assuming the SPT N-values were determined using a 140- lb donut drop weight and SPT N-values shall be corrected with a hammer efficiency correction factor (CE) of 0.75. Figure 1806.4 is intended to be a screening tool for Site Classes A through D, determined in accordance with section 1613.5.2. The figure is based on Maximum Considered Geometric Mean Earthquake (MCEG) Peak Ground Accelerations (PGAs) at outcropping Site Class B rock of 0.25 g, 0.18 g, and 0.12 g and site amplification factors (FPGA) of 1.35, 1.44, and 1.56, respectively for Site Class D, and a factor of safety of 1.1. Refer to Table 1604.11 or USGS earthquake hazard data for PGA specific to where the site is located. This figure is based on observed behavior of clean sand, and is conservative for other (more silty) materials. Soils that do not screen out using Figure 1806.4 shall be evaluated for liquefaction per section 1803.5.12.
If the SPT N60-values plot above or to the right of the applicable line in Figure 1806.4, the soil shall be considered not susceptible to liquefaction. Liquefaction for soils below a depth of 60 feet (18 m) from final grade need not be considered for level ground. For pressure-injected footings, the tenfoot (3-m) thickness of soil immediately below the bottom of the driven shaft shall be considered not susceptible to liquefaction.
1806.4.2Compacted Fills. Compacted granular fills shall be considered not susceptible to liquefaction provided that they are systematically compacted to at least 93% of the maximum dry density determined in accordance with ASTM Standard Method D1557.1806.4.3Evaluation by a Registered Design Professional. Soils that do not meet the criteria in section 1806.4.1 or 1806.4.2 shall be considered potentially susceptible to liquefaction. For these cases, studies shall be performed by a registered design professional in accordance with section 1803.5.12.1806.4.4Lateral Sliding. For sites underlain by the saturated soils identified in section 1806.4, and where the ground surface at the site or adjacent to the site is sloping such that lateral sliding (slope instability) may occur, studies by a registered design professional shall be made to establish the safety against sliding and lateral deformations as a result of the design earthquake. Click to view image
1807.1.6 Revise subsection as follows
1807.1.6 Prescriptive Design of Concrete and Masonry Foundation Walls. Concrete and masonry foundation walls shall be permitted to be designed and constructed in accordance with this section, provided that they are laterally supported at the top and bottom, not subject to net hydrostatic pressures or surcharge loadings, and the backfill adjacent to the walls is not subjected to heavy compaction loads.1807.2 through 1807.2.3 Replacesection and subsections with 1807.2 through 1807.2.6 as follows:
1807.2 Retaining Walls. Retaining walls shall be designed in accordance with sections 1807.2.1 through 1807.2.6. The requirements of this section shall apply to any type of retaining structure or system that has any portion of its exposed face inclined steeper than one horizontal to one vertical, including conventional retaining walls, crib and bin wall systems, reinforced or mechanically stabilized earth systems, anchored walls, soil nail walls, multi-tiered systems, boulder walls or other types of retaining structures. The requirements of this section do not apply to slope facings, armor or riprap placed for the sole purpose of protection against surface erosion.1807.2.1Design. Retaining walls shall be designed to resist the static and seismic pressures of the retained materials, water pressures, and dead and live load surcharges to which such walls are subjected, and to ensure stability against excessive movements, overturning, sliding, excessive foundation pressure, and water uplift. Retaining walls that support an unbalanced height of retained material greater than six feet (1.83 m), or any retaining system or slope that could impact public safety or the stability of an adjacent structure shall be designed by a registered design professional.1807.2.2Design Lateral Soil Loads. Retaining walls shall be designed for the lateral soil loads set forth in section 1610, including seismic lateral pressure, or the lateral loads determined by a registered design professional based on a geotechnical investigation performed in accordance with section 1803.1807.2.3Safety Factor. Retaining walls shall be designed to resist sliding and overturning with a minimum factor of safety of 1.5 in each case. The load combinations of section 1605 shall not apply to this requirement. Instead, design shall be based on 0.7 times nominal earthquake loads, 1.0 times other nominal loads, and investigation with one or more of the variable loads set to zero. The safety factor against lateral sliding shall be taken as the available soil resistance at the base of the retaining wall foundation divided by the net lateral force applied to the retaining wall. EXCEPTION: Where earthquake loads are included, the minimum factor of safety for retaining wall sliding and overturning shall be 1.1.
1807.2.4Overall Stability. The overall global stability of a retaining wall, considering potential failure surfaces extending through the materials located below, in front of and behind the wall shall be evaluated.1807.2.5Discrete Elements. For retaining walls constructed of discrete elements, such as unmortared masonry, rock, boulders, or stacked modular units, the elements shall be bonded or fastened together to prevent dislodgement under static and seismic loading conditions where dislodgement of the elements could pose a risk to public safety.1807.2.6Wall Drainage. Retaining walls shall be designed to support a hydrostatic head of water pressure equal to the full height of the wall, unless a drainage system is provided to reduce or eliminate hydrostatic pressure on the wall. Drainage systems shall be designed with sufficient permeability and discharge capacity, and shall be provided with appropriate filters and other design features to prevent blockage due to siltation, clogging, or freezing.1808.2 Revise section as follows:
1808.2Design for Capacity and Settlement. Foundations shall be designed to provide adequate load bearing capacity while limiting settlement, heave and lateral movement to tolerable levels. Foundations in areas with expansive soils shall be designed in accordance with the provisions of section 1808.6.FIGURE 1808.7.1 FOUNDATION CLEARANCES FROM SLOPES
Figure 1808.7.1 Insert H @ Vertical Dimension Line1809.14 Insert section as follows.
1809.14Ground Improvement.Ground Improvement, for purposes of this Section, shall be defined as a system that uses elements of aggregate, concrete, grout, or other mixture of cementitious materials and/or aggregates, or other materials that are significantly stiffer than the ground being improved, installed into the ground upon which building foundation units such as footings, slabs or mats are supported, to improve the engineering properties of the bearing strata. The Ground Improvement system includes the elements and all strata and materials within the zone of influence beneath the foundation units. This Section provides requirements for the design, testing and construction of Ground Improvement systems.
1809.14.1Design. Ground Improvement for foundation unit support shall be designed by a registered design professional, referred to in this Section as the Ground Improvement Designer.1809.14.1.1Design Determinations. Ground Improvement design shall include the determination of the following, at a minimum: 1. Applied loads on the Ground Improvement system including the following: a. Compression, tensile and lateral loads, static and dynamic.2. Load distribution and strain compatibility between Ground Improvement elements and the surrounding soil being improved, considering all loading conditions.3. Lateral confinement and the potential for element bulging or necking.4. Seismic response including kinematic movements, and potential for liquefaction and its impact on bearing, settlements and confinement.5. Allowable geotechnical capacity (vertical, and lateral if applicable) of individual Ground Improvement elements and groups of elements.6. Allowable structural capacity (axial, flexure, and shear) of individual Ground Improvement elements consistent with the allowable stresses for the materials listed in Table 1810.3.2.6.7. Structural compatibility between Ground Improvement elements and the supported foundation units including:a. Confirmation of the thickness and characteristics of any granular Load Transfer Pad to separate the foundation units from the elements and the improved ground, as applicable.b. Evaluation of potential impacts of concentrated reaction loads imposed by the elements on supported foundation units including floor slabs.c. Minimum number and configuration of elements to establish vertical, lateral and rotational stability of isolated and strip footings.8. Short-term and long-term settlements of foundations and other structural units bearing above Ground Improvement systems.9. Potential impacts of Ground Improvement element installations on previously-installed elements and on existing facilities in the proximity of element installations.1809.14.1.2Rigid Inclusions. Rigid Inclusions, for purposes of this Section, shall be defined as Ground Improvement elements comprised of or containing concrete, cement grout or materials of similar stiffness. Ground Improvement using Rigid Inclusions shall conform to the following additional requirements.
1. The allowable geotechnical load capacity of Rigid Inclusions shall not exceed fifty (50) percent of the demonstrated maximum load capacity as determined by load testing in accordance with Section 1809.14.2.2. The allowable geotechnical load capacity of a foundation unit shall not exceed forty (40) percent of the ultimate load capacity of the modified bearing strata beneath the unit, considering the combined contribution of the ultimate bearing capacity of the subsurface strata and the demonstrated maximum load capacity of the Ground Improvement elements.3. The allowable geotechnical load capacity of a foundation unit shall be equal to or greater than the foundation unit's bearing area multiplied by the design foundation bearing pressure indicated on the foundation design drawing(s) or otherwise specified by the registered design professional responsible for the foundation unit structural design.4. A Load Transfer Pad consisting of a minimum of 6 in. of 3/4 in. crushed stone, or other material and thickness with equivalent load-deformation characteristics and shear resistance, shall be provided between tops of Rigid Inclusions and the underside of foundation units. If thicker than 8 inches, the resistance of the Load Transfer Pad to punching by the elements shall be demonstrated by analysis or testing.5. Determination of allowable load capacity of Rigid Inclusions by load testing such that anticipated foundation settlements are tolerable and protective of the integrity of the supported structure.1809.14.1.3Design Documentation. Documentation of Ground Improvement design shall be prepared by the Ground Improvement Designer and provided to the building official and the building owner, which includes the following at a minimum. 1. Detailed description of the proposed Ground Improvement elements and other system components.2. Key assumptions used in system design.3. Element allowable design load and minimum diameter.4. Subsurface conditions within zone of influence below foundation units including bearing strata, design element penetration into bearing strata, and proportion of capacity anticipated to be achieved in friction and end-bearing.5. Potential impacts of the presence of soft, organic or compressible soils.6. Process, equipment, materials and criteria for element installations.7. Measures to achieve and to confirm element shaft integrity, and accommodate the presence of soft or organic soils.8. Requirements for load testing.9. Description of the results, including calculations, of design determinations required in Sections 1809.14.1.1 and 1809.14.1.2.10.Ground Improvement design drawing(s) including layout and dimensions of supported foundation units; foundation unit design structural loads and allowable bearing pressures; element locations, diameters and allowable design loads; and minimum element spacing.1809.14.2Rigid Inclusion Load Testing. Load testing of Rigid Inclusions shall be performed at on-site location(s) representative of the subsurface conditions at production element locations, to determine the allowable design load in vertical compression and adequate element performance for the Ground Improvement system. Testing shall be performed in accordance with the following requirements: 1.Load in Bearing Stratum. The load reaching the top of the bearing stratum under the maximum test load shall not be less than the following: a. For end-bearing elements: 100% of the allowable design load.b. For friction elements: 150% of the allowable design load.c. For elements designed for a combination of end-bearing and friction, the required test load reaching the bearing stratum shall be based on the predominant support mode.2.Instrumentation. The test element shall be instrumented using redundant systems of strain gauges, tell-tales, or other methods to enable measurement or computation of the load in the element where it enters the bearing stratum. For foundation elements containing grout or concrete, instrumentation shall be installed to permit direct measurement of the elastic modulus of the element during the test.3.Loading Procedure. The loading procedure shall be as follows: a. Apply 25% of the proposed allowable design load every 0.5 hour. Longer time increments may be used, but each time increment should be the same. In no case shall a load be changed if the rate of settlement is not decreasing with time.b. At 200% of the proposed allowable design load, maintain the load for a minimum of one hour and until the settlement meets the criteria in Section 1809.14.2.4.c. Remove 50% of the design load every 15 minutes until zero load is reached. Longer time increments may be used, but each should be the same.d. Measure rebound at zero load for a minimum of one hour.e. For each load increment or decrement, take readings at the top of the element and on the instrumentation at one, two, four, eight and 15 minutes and at 15- minute intervals thereafter.f. A load greater than 200% of the proposed allowable design load may be applied at the top of the test element, using the above loading procedure, to ensure that the requirement for minimum load reaching the bearing stratum is fulfilled. Other optional methods may be approved by the building official upon submittal in advance of satisfactory justification prepared by a registered design professional.4.Load Test Evaluation. Provided that the requirement for minimum load reaching the bearing stratum is satisfied, the element allowable design load shall be determined by the Grojhnm,und Improvement Designer. The allowable design load shall not exceed 50 percent of the demonstrated maximum load capacity, defined as the load at which the settlement at the top of the element does not exceed 0.01 in. during one hour, and 43 which provides the minimum factor of safety and settlement control required by the Building Code.5.Documentation. The results of the load testing, including the testing methodology, system setup, demonstrated maximum load capacity, allowable design load and acceptance criteria shall be documented in a report prepared by the Ground Improvement Designer.1809.14.3Construction.1. Elements and other aspects of the Ground Improvement system shall be constructed and installed in accordance with the Ground Improvement design.2. Special inspections with documentation shall be performed in accordance with the procedures of Chapter 17, continuously during all construction activities related to Ground Improvement including but not limited to materials, load testing, element installation, element cut-offs, subgrade preparation, Load Transfer Pads and any fill placed between elements and footing bottoms.3. As-built drawing(s) and other information as required to document the Ground Improvement system installations and related activities shall be prepared and made available to the building official and the building owner, sealed by the Ground Improvement Designer. The information shall include, at a minimum, the load test report, the final foundation unit layout, element locations and cut-off elevations, and any deviations between the Ground Improvement design and the as-built conditions.1810.1.2Revise subsection as follows: 1810.1.2Use of Existing Deep Foundation Elements. Deep foundation elements left in place that have previously supported a partially or fully demolished structure may be used for support of new construction if satisfactory evidence is submitted by a registered design professional to the building official which indicates that the foundation elements have not been adversely impacted by the demolition, are structurally sound, have adequate load-bearing capacity to support the new design loads, and meet all of the requirements of 780 CMR. The load-bearing capacities of the deep foundation elements shall be determined by one of the following methods:1. Analyses to determine the actual sustained load that the foundations supported satisfactorily in the previous structure.2. Analyses based on documented foundation geometry and presumptive bearing value of the supporting soil, where applicable to the foundation type.3.Load testing or re-driving performed on representative foundation elements. Records of previous pile-driving and load testing may be utilized where such records are deemed adequate by the registered design professional.1810.3.2.6Insert the following exceptions: EXCEPTIONS:
1. Maximum allowable stress for concrete or grout in compression for elements that are cast in place without a permanent casing shall be 0.33 f'c.2. Maximum allowable stresses for timber foundation elements shall be 80% of the values determined in accordance with the AWC NDS.1810.3.3.1 Replace subsection as follows:
1810.3.3.1Allowable Axial Load. The allowable axial load on a deep foundation element shall be determined in accordance with sections 1810.3.3.1.1 through 1810.3.3.1.11. here the allowable load capacity is not determined by using one of the formulas or analysis methods provided in sections 1810.3.3.1.1 through 1810.3.3.1.11, or the presumptive load- bearing values in section 1806, the allowable load capacity shall be verified by load tests. Dynamic load testing of instrumented driven piles performed in accordance with ASTM D4945 may be used in lieu of static load testing, where the testing program consists of a minimum of three instrumented piles tested to a minimum factor of safety of 2.5 using an analysis procedure that matches the force and velocity traces measured at the top of the pile. Load testing may be waived by the building official based upon submittal of substantiating data prepared by a registered design professional which include load test data or performance records for the proposed deep foundation elements under similar soil and loading conditions. EXCEPTION: The allowable frictional resistance of cast-in-place elements greater than or equal to 12 inches in diameter obtaining capacity in Material Classes 1 through 6 in Table 1806.2a may be determined by a registered design professional based on analyses incorporating results of testing in similar bearing materials.
1810.3.3.1.1 through 1810.3.3.1.3 Replace as follows: 1810.3.3.1.1Driving Criteria. or driven piles with a design load capacity not exceeding 50 tons (445 kN), the allowable load capacity may be determined based on final driving criteria (net displacement per hammer blow) obtained from an appropriate pile driving formula using a factor of safety not less than 3.5, or from wave equation analysis using a factor of safety not less than 2.75. he use of followers shall be allowed only as directed by a registered design professional. The introduction of fresh hammer cushion material just prior to final penetration is not permitted.
1810.3.3.1.2Load Tests. here static load testing is required to determine the allowable load bearing capacity of deep foundation elements in vertical compression, the load tests shall be performed in accordance with ASTM D1143 and the following requirements:1.Load in Bearing Stratum. he load reaching the top of the bearing stratum under the maximum test load shall not be less than the following: a. For end-bearing elements: 100% of the allowable design load.b. For friction elements: 150% of the allowable design load.c. For foundation elements designed for a combination of end-bearing and friction, the required test load reaching the bearing stratum shall be based on the predominant support mode.2.Instrumentation. The test element shall be instrumented using strain gauges, tell-tales, or similar methods to enable measurement or computation of the load in the element where it enters the bearing stratum. For foundation elements containing concrete, instrumentation shall be installed to permit direct measurement of the elastic modulus of the element during the test. Instrumentation of the test element is not required for the following cases:
a. The test element is installed within a casing that extends to within ten feet above the bearing stratum.b. Load testing is performed on an existing foundation element, and appropriate consideration is given to potential frictional resistance developed above the bearing stratum during the load test.c. The foundation element length does not exceed 30 feet and no appreciable load will be supported above the bearing stratum.3.Loading Procedure. he loading procedure shall be as follows:a. Apply 25% of the proposed allowable design load every 0.5 hour. Longer time increments may be used, but each time increment should be the same. In no case shall a load be changed if the rate of settlement is not decreasing with time.b. At 200% of the proposed allowable design load maintain the load for a minimum of one hour and until the settlement (measured at the lowest point on the element at which measurements are made) over a one-hour period is not greater than 0.01 in.c. Remove 50% of the design load every 15 minutes until zero load is reached. Longer time increments may be used, but each should be the same.d. Measure rebound at zero load for a minimum of one hour.e. For each load increment or decrement, take readings at the top of the element and on the instrumentation at one, two, four, eight and 15 minutes and at 15-minute intervals thereafter.f. A load greater than 200% of the proposed allowable design load may be applied at the top of the test element, using the above loading procedure, to ensure that the requirement for minimum load reaching the bearing stratum is fulfilled. Other optional methods listed in ASTM D1143 may be approved by the building official upon submittal in advance of satisfactory justification prepared by a registered design professional.1810.3.3.1.3Load Test Evaluation Methods. rovided that the requirement for minimum load reaching the bearing stratum is satisfied, the allowable design load is permitted to be the greater of the following:1. Allowable design load based on settlement during loading: 50% of the applied test load which causes a gross settlement at the top equal to the sum of: a) the theoretical elastic compression of the element in inches assuming all the load at the top is transmitted to the tip, plusb) 0.15 inch (3.8 mm), plusc) 1% of the tip diameter or width in inches.2. Allowable design load based on the net settlement after rebound: 50% of the applied test load which results in a net settlement at the top of 0.5 inch (13 mm) after rebound at zero load. If the allowable design load is not governed by one of the above criteria, the allowable design load shall be equal to 50% of the maximum test load.
If the requirement for minimum test load reaching the bearing stratum is not satisfied, the allowable design load shall not exceed:
a) the load reaching the bearing stratum for end- bearing elements andb) two-thirds of the load reaching the bearing stratum for friction elements. The allowable design load capacity determined from load tests can be applied to other foundation elements of the same type and size that are installed in similar subsurface conditions using the same installation methods and equipment. Where the design is based on a minimum embedment length, minimum penetration resistance, or friction over a minimum surface area, the applicable design value for the production elements shall equal or exceed the value used for the test element.
1810.3.3.1.10 Add subsection as follows:
1810.3.3.1.10Enlarged Base Piles. For enlarged base piles with compacted concrete bases and design capacities up to 120 tons, that are formed on or in bearing materials of Classes 1 to9 inclusive in Table 1806.2a, the allowable load may be computed by the following formula. The Class 9 material (fine sand) shall have a maximum of 15% by weight finer than the No. 200 mesh sieve and the fines shall be non-plastic.
R = [(B x E)/C] V 2/3(Equation 18-12)
Where:
R = allowable load in pounds.
B = average number of blows required to inject one cubic foot of concrete, during injection of the last batch.
E = energy per blow in foot-pounds.
C = constant.
V = total volume of base concrete in cubic feet.
The values of R, E, and C shall conform to Table 1810.3.3.1 unless other values are determined by load test, in which case the latter values shall control. The value of V shall include an allowance of one standard batch volume of concrete, if concrete is used in the tube during the driving process, plus the additional volume of concrete injected during formation of the base.
During injection of the last batch of concrete in the base, the height of concrete within the drive tube shall not be more than 1/3 of the drive-tube inside diameter.
TABLE 1810.3.3.1
R (tons) | Energy, E (foot-pounds) | C | Standard Batch Volume (ft3) |
over 100 | 140,000 | 18 | 5 |
51 to 100 | 100,000 | 18 | 5 |
25 to 50 | 60,000 | 30 | 2 |
1810.3.3.1.11 Add subsection as follows: