N.J. Admin. Code § 19:6-2.25

Current through Register Vol. 56, No. 24, December 18, 2024

Section 19:6-2.25 - Bearing capacity of nominally unsatisfactory bearing materials

(a) Whenever soils exploration shows that the proposed foundation would rest on, or be underlain by, nominally unsatisfactory bearing materials, a report based on soil tests and foundation analysis (including analysis of undisturbed samples) shall be submitted by an architect or engineer, demonstrating, subject to approval of the chief engineer, that the proposed construction under a condition of 100 percent overload is safe against failure of the soil materials. The report shall also show that the probable total magnitude and distribution of settlement to be expected under design conditions will not result in instability of the building or stresses in the structure in excess of the allowable values established in this subchapter. In addition, the following provisions shall apply:

1. Fill materials:

i. Controlled fills: Fills shall be considered as satisfactory bearing materials of class 6-65 or 7-65 when placed in accordance with the following procedures, under the provisions for controlled inspection:

(1) Before placement of fill, the existing ground surface shall be stripped of all organic growth, timber, rubbish, and debris. After stripping, the ground surface shall be compacted to the density described in item (4) below.

(2) Materials for fill shall consist of sand, gravel, crushed stone, crushed gravel, or a mixture of these, and shall contain no organic matter. The fill materials shall contain no particles exceeding four inches in the largest dimension. No more than 30 percent of the material shall be retained on a 3/4 inch sieve. The material passing the 3/4 inch sieve shall contain, by weight, no more than 45 percent passing the 100 sieve, or 12 percent passing the 200 sieve.

(3) The grading of the fill shall be determined in accordance with the applicable procedures of Sec. MBA-611.0, National Standard for Foundations in the Manual for the Standard Building Code of New Jersey.

(4) Fill shall be placed and compacted at its optimum moisture content, in uniform layers not more than 12 inches thick (after compaction) and each layer shall be thoroughly compacted to a density of not less than 95 percent of the density prescribed in National Standard for Foundations. The field density shall be verified by in-place density tests made on each lift of the embankment. Fill shall not be placed when frozen or placed on a frozen or wet subgrade.

ii. Uncontrolled Fills: Fill material, other than controlled fill, may not be used for the support of buildings unless its use can be adequately demonstrated to the chief engineer.

2. Organic silts, organic clays, soft inorganic clay, loose inorganic silt and varved silt:

i. The allowable bearing pressure shall be determined independently of table 613.7, subject to the following:

(1) For varved silts, the average unit intensity of loading produced by the proposed building shall not exceed two tons per square foot, except that for desiccated or preconsolidated soils, higher bearing pressures will be allowed.

(2) Organic silts or clays (Groups OL and OH) or soft or loose soils of Groups ML, CL, MH and CH may not be assigned an allowable bearing pressure unless the procedures for their use have been clearly demonstrated to the satisfaction of the chief engineer.

ii. The report described in the introduction to this section shall contain, as a minimum, the following information:

(1) Subsurface profiles through the area defining the stratigraphy;

(2) Sufficient laboratory tests data on the compressible material to indicate the coefficient of consolidation, coefficient of compressibility permeability, secondary compression characteristics, and Atterberg limits;

(3) Where the design contemplates improvement of the natural bearing capacity and/or reduction in settlements by virtue of preloading, cross sections showing the amount of fill and surcharge to be placed and design details showing the required time for surcharging shall be indicated, and computations showing the settlement to be expected during surcharging. Records of settlement, plate elevations and pore-pressure readings, before, during and after surcharging shall be filed with the chief engineer.

(4) The estimated amount and rate of settlement expected to occur after the structure has been completed, including the influence of dead and live loads of the structure;

(5) A detailed analysis showing that the future settlement will not adversely affect the performance of the structure;

(6) Where sand drains are to be used, computations showing the diameter, spacing, and method of installation of such drains shall be provided.

3. Artificially treated soils: Nominally unsatisfactory soil materials that are artificially compacted, cemented, or preconsolidated (including soils compacted by vibration, cemented by chemical injection, or preconsolidated by use of electric current, but not including cases where preconsolidation consists solely of the use of surcharge with or without sand drains) may be used for the support of buildings, and nominally satisfactory soil materials that are similarly treated may be used to resist soil bearing pressures in excess of those indicated in table 613.7 for the soil in its natural state, subject to the following:

i. The vertical and lateral extent of the soil that is compacted, cemented or preconsolidated shall conform to the full extent of the distribution of loading that is assumed for purposes of computing the intensities of the soil bearing pressure. The actual soil bearing pressure shall not exceed the limitations of this section for nominally unsatisfactory bearing materials or, for satisfactory bearing materials, shall not exceed the limitations of table 613.7.

ii. After the treatment procedure, a minimum of one boring shall be made for every 1,600 square feet of that portion of the building area that is supported on treated soil, and a sufficient number of samples shall be recovered from the treated soil to demonstrate the efficacy of the treatment.

N.J. Admin. Code § 19:6-2.25