Paraphrase the fallowing WORD document

XYZ Development, LLC has requested ASU Geotechnical, Inc. to organize a geotechnical evaluation with recommendations regarding foundation for three planned structures. XYZ Development, LLC has planned to construct a three-story medical tower, a one-story office building, and a multi-story parking garage on a 10-acre property that is in West Memphis, AR. In addition, an 18-feet high retaining wall is planned to be constructed on the north side of the parking garage. 

ASU Geotechnical, Inc. was provided with soil data included a log of a borehole that extended to a depth of 100 feet. Has recommended a 6’ x 6’ shallow foundation for the one- story building at depth of 5 feet. The expected settlement under the foundation for the parking garage was calculated to be 1.09 inches, and the expected settlement for the medical tower was calculated to be 0.78 inch. Also, ASU Geotechnical, Inc. has recommended a drilled shaft deep foundation design to be used for the three-story medical tower. Furthermore, for the 3-story medical tower the pile should have a diameter of 48 inches and reach a depth of 40 feet below the ground surface with a total of 2 piles required per column. For the multi-story parking garage, a drilled shaft should have a diameter of 48 inches and reach a depth of 70 feet below the ground surface with a total of 2 piles required per column. 

The expected total differential settlement for the parking garage was calculated to be 0.31 inches, and the total differential settlement for the tower was calculated to be 0.23 inch. The recommended dimensions for the retaining wall include a 12-foot-wide footing base with 1.5-foot thickness. The entire retaining wall should have a total height of 20 feet, with only 18 feet above the ground surface. The 0.5 foot of soil above the toe was placed to adjust the effects of sliding of the wall. The base of the stem wall should have a thickness of 1.5-foot, and the top of the stem wall should have a thickness of 8 inches. Also, the factor of safety for sliding was calculated to be 1.59, the factor of safety for the bearing capacity was calculated to be 2.78

Introduction

XYZ Development, LLC in planning to construct residential and commercial facilities on a 10-acre property that is in West Memphis, AR the largest city in Crittenden County. The property will include a one-story office building, a three-story medical tower, and a multi-story parking garage with an 18-feet high retaining wall on the north side of the parking garage. The expected maximum column load for the one- story office building would be 50 kips, 350 kips for the three-story medical tower, and 900 kips for the parking garage. The dead load was expected to be 65 % of the maximum column load with column spacing at 35 feet. ABC Engineering, Inc. has requested ASU geotechnical Inc. to submit a geotechnical report that included: shallow foundation recommendations, total and different settlements under the maximum column load in the parking garage and the shopping center, analysis of various types of deep foundations for the residential tower structure and parking garage, and stability analysis of the retaining wall, and the most suitable type of foundation system.

Site Condition

The project site was an established field that is located on the north side of West Memphis, AR. Interstate 40 Frontage Road E and North 7th Street crossing the requested site to the south and east sides. Crittenden County is a rich, cottons farmland with the Mississippi River forming the eastern boundary. The county population is 48,730 and with an area of 636 square miles, Climate conditions range in the summer season from 70 to 90 F. while, in the winter season the climate conditions range from 31 to 50 F°. Figure.1 below shows the site location.

Figure.1 Baptist Memorial Hospital location map

Site Geology

Geological studies by geotechnical engineers point out that the site is primarily underlain by Quaternary age alluvium. The alluvium formation is described as consisting of silt, sand, clay, and gravel includes some terrace deposits and glacial drift of Pleistocene age in some areas. However, The clay ranges from light brown to red with medium stiff to very stiff conditions, and the sand ranges from light orange and pink to tan with very dense conditions. The gravel and silt range from light grey to tan with very stiff to very dense conditions.

Fieldwork and Laboratory Testing Descriptions

boreholes were extended to a depth of 100 feet below the current ground surface, and the fieldwork utilized a safety hammer. Disturbed samples were collected using Standard Penetration Tests (STPS) at selected intervals up to 100 feet deep. Overall, SPT N values ranged from 10.5 to 49 with an average of about 29.8. Therefore, N values between 11 to 51 are suggestive of a medium stiff clay or loose sand. Also, medium dense sand and stiff clay are considered by N values greater than 10.5 and dense sands have N values of 65. The groundwater was found at a depth of 18 feet at the end of the fieldwork. Laboratory testing was performed on the collected soil samples from the project site.

Subsurface Condition

The subsurface profile contains primarily of eight different soil horizons of closely varying amounts of clays, sand, and gravels as described in here. The first underlying soil horizon is described as a brown, medium to stiff, Clayey Silt (ML), and this horizon extends to a depth of 18 feet below the ground surface. The second underlying soil horizon is described as brown-gray, medium to very stiff, High Plasticity Clay. This horizon varies in color throughout the 20 feet layer depth. The third underlying soil horizon is described as light brown, stiff to very stiff, Clay This horizon varies in color to light gray, orange and tan with sand throughout the 10 feet layer depth. The fourth soil horizon is described as brown and red, very dense condition, Clayey Sand. This horizon is at a depth of 5 feet. The fifth soil horizon is described as light orange and pink, very dense condition, Sand. The soil horizon also contains silt with a depth of 5 feet. The sixth underlying soil horizon is described as a light gray and orange brown, very stiff, Silty Clay with Sand (CL-ML). This horizon is at a depth of 5 feet. The seventh soil horizon is described as tan, very dense condition, Silty Sand. The soil horizon is at a depth of 15 feet with light gray in the middle of the layer. The final soil horizon is described as dense to very dense condition, Gravel with silt and Sand (GP-GM). This horizon is at a depth of 21 feet.

Shallow Foundations

The project has a ground elevation of 215 feet, and the shallow foundation analysis was performed for the three structures by using both methods Terzaghi's and Vesic's Bearing Capacity Methods and the most economical value of the two methods was chosen. Vesic's method raised the value of the base (B). On the other hand, Terzaghi’s method value was more efficient economically. Furthermore, shallow foundation was assumed to be 210 feet, which provided a depth of 5 feet level with the ground surface. A factor of safety was chosen to be 3 for the office building, the 3-story medical tower, and the parking garage. The 50-kip one-story office building was designed to adjust a 6’ x 6’ square footing. The 350-kip three-story medical tower was designed to adjust a 16.5' x 16.5’ square footing. The 900-kip multi-story parking garage was designed to support the structure with a 26.5’ x 26.5’ square footing. Table 1. Below shows the shallow foundation footing size.

Table.1 Shallow Foundation Footing Size

Settlement Analysis

After the shallow foundations were designed, the settlement of the soil layer was calculated by using Skempton & Bjerrum’s method. The settlement for each structure was determined by using over consolidated soils Case I, since ’c > ('z + z. Table 2. Shows the total settlement for the maximum column load, and the total for the maximum column dead load.

Table 2. Total Settlement Analysis

The differential settlement for the medical tower and the parking garage were found by subtracting the maximum settlement from the settlement for the dead load in each structure. Table 3. Shows the value of differential settlement for each structure.

Table 3. Total Differential Settlement

Deep Foundation

The analysis of various types of deep foundation for the 3-story residential tower and the multi-story parking garage were performed to adjust the maximum column load of the two structures. The two types of foundations considered include a 14-inch reinforced concrete pile, an 18-inch auger-cast, and a 48- inch drilled shaft, all of which were analyzed at depths of 40 feet and 70 feet as shown in Table 4.

Table 4. Deep Foundation Capacities

Both of square concrete and auger-cast systems are types of piles for deep foundations. However, the square concrete piles are formed reinforced concrete members that are driven deep into the ground. Also, the drawbacks of using reinforced concrete piles are expected to the doubt of the concrete pile to become damaged during the handling or driving of the pile. Although, the concrete pile tends to be efficiently economical whenever it is compared to the steel piles. The auger-cast pile is a pile system that is cast-in- place at the project site. A hollow-stem auger is used to drill into the ground at which time period a cement grout is added under high pressure, to prevent the drilled hole from collapsing on itself from lateral pressure of the surrounding soil. Drilled shafts are another form of deep foundation system that is a cast-in-place method, and large loads can be supported by drilled shafts. Which those can be economical when one drilled shaft is used to replace multiple pile systems.

Deep foundations were used to help spread large loads from the foundation to the soil as a mean of the side friction, and the end bearing pressure. Therefore, the end bearing pressure helps to transfer the load to the bottom of the deep foundation. Which it gets absorbed by the soil underneath and accounts for the downward load on the foundation. Furthermore, side friction is the friction that occurs between the sides of the deep foundation with the surrounding soil. The ultimate bearing capacity was found by summing the side friction and end bearing pressure. The total allowable bearing capacities was found by dividing the ultimate bearing capacity by the factors of safety with piles using 2.5 and drilled shafts using 3. The change in the soil layers was determined to calculate the end bearing capacity and the side friction.

ASU Geotechnical, Inc. was requested to determine the number of piles that are required to support the maximum column load for both the three-story residential tower and the multi-story parking garage. The number of piles for each structure were calculated by diving the column load by the total allowable downward capacity. Table 5. and Table 6. show the number of piles that are required for each structure.

Table 5. Require Piles for The Parking Garage

Table 6. Require Piles for The Residential Tower

Stability Analysis of the Retaining Wall

The retaining wall was designed to prevent sliding, overturning, and bearing capacity. The proposed development for an 18-feet retaining wall is to be planned on the north side of the parking garage. The dimensions of the retaining wall were adjusted until the wall could counter the resisting forces to act on the wall. Also, the calculations were performed by assuming the excavation of soil that was performed to adjust the retaining wall design. Therefore, the base of the retaining wall was assumed to be resting on top of the clayey layer of soil. The clayey soil could be excavated and replaced with a soil that has a higher angle of internal friction. Such as sand, which the sand could help counter the resisting forces and possibly lower the cost of materials. Furthermore, cost analysis of the soil replacement is recommended before further excavation and soil backfill is to be considered as well. Alternative methods exist when it comes to the prevention of the retaining wall from sliding and overturning. Such as, extending the toe or heel of the footing, adding a key beneath the footing, using a stronger backfill soil, and installing tiedown or tieback anchors. Also, the factor of safety for sliding was calculated to be 1.59, the factor of safety for the bearing capacity was calculated to be 2.78.

Recommendations

ASU Geotechnical, Inc. was requested to submit a lab report that includes several tests and recommendations. Therefore, ASU Geotechnical, Inc. recommended that the one-story office building should have a square shallow foundation with dimensions of 6' x 6' feet with an elevation depth of 5 feet below the ground surface. Also, the three-story medical tower should have a group of two 48-inch diameter drilled shafts at a depth of 40 feet for each column; with using the minimum number of shafts. ASU Geotechnical, Inc. also recommended a two 48-inch diameter drilled shafts at a depth of 70 feet for each column of the parking garage with using the minimum number of shafts. ASU Geotechnical, Inc. recommended that the 18 feet retaining wall dimensions with 12 feet footing base and a 1.5-foot thickness. The entire retaining wall should have a total height of 20 feet, with only 18 feet above the ground surface. The 0.5 foot of soil above the toe was placed to adjust the effects of sliding of the wall. The base of the stem wall should have a thickness of 1.5-foot, and the top of the stem wall should have a thickness of 8 inches. Also, the factor of safety for sliding was calculated to be 1.59, the factor of safety for the bearing capacity was calculated to be 2.78.

References

1. Coduto, D. P. (2001). Foundation Design: Principles and Practices. Upper Saddle River: Prentice-Hall.