Geotechnical Reports

1.

INTRODUCTION The proposed construction of a circular cylindrical chemical tank inside the Chemical 164 factory located in Pandacan, Metro Manila required a geotechnical investigation to determine the extent, nature and characteristics of the subsurface soils/materials at the foot of the chemical tank. The findings of this investigation were used to facilitate the geotechnical and structural designs, and the construction of the foundations for the chemical tank. The perspective view of the site is shown below:

Figure 1. Perspective view of the Chemical Tank in Pandacan, Manila

2.

PROPOSED STRUCTURE

2.1

Dimensions The tank has a diameter of 15 meters and a height of 12 meters. It has a chemical with a unit weight of 12.0kN/m^3. The depth of embedment is 2.0 meters from the existing ground.

2.2

Load The total weight of the tank can be computed by adding the weight of the empty tank, with the weight of the chemical, assuming the tank is full. The weight of the empty tank can be computed assuming a thickness of 50mm. Thus, the weight is computed as: 𝑊𝑒𝑚𝑝𝑡𝑦 𝑡𝑎𝑛𝑘 = 𝑉𝑜𝑙𝑢𝑚𝑒𝑒𝑚𝑝𝑡𝑦 𝑡𝑎𝑛𝑘 ∗ 𝛾𝑠𝑡𝑒𝑒𝑙

𝑊𝑒𝑚𝑝𝑡𝑦 𝑡𝑎𝑛𝑘

𝜋 ∗ 𝑑2 = [( ∗ 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠) + (𝑑 ∗ 𝜋 ∗ ℎ ∗ 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠)] ∗ 𝛾𝑠𝑡𝑒𝑒𝑙 4

𝑊𝑒𝑚𝑝𝑡𝑦 𝑡𝑎𝑛𝑘

𝜋 ∗ 152 = [( ∗ 0.05) + (15 ∗ 𝜋 ∗ 14 ∗ 0.05)] ∗ 78.9705 4 𝑊𝑒𝑚𝑝𝑡𝑦 𝑡𝑎𝑛𝑘 = 3302.739962 𝑊𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙 = 𝑉𝑜𝑙𝑢𝑚𝑒𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙 ∗ 𝛾𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙 𝑊𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙 = (

𝜋 ∗ 𝑑2 ∗ ℎ) ∗ 𝛾𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙 4

𝜋 ∗ 152 𝑊𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙 = ( ∗ 14) ∗ 12 4

𝑊𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙 = 29688.05058𝑘𝑁 𝑊𝑡𝑜𝑡𝑎𝑙 = 𝑊𝑒𝑚𝑝𝑡𝑦 𝑡𝑎𝑛𝑘 + 𝑊𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙 𝑊𝑡𝑜𝑡𝑎𝑙 = 32990.79054𝑘𝑁 Assuming 10 of a specific type of foundation will carry the load, each would carry a load of 3,299.079065kN.

3.

DETAILS OF SITE INVESTIGATION One borehole was drilled to find the types and succession of underlying soil/rock strata and their corresponding geotechnical properties in the relevant land area. Soil samples were taken from the borehole during drilling with the use of a standard split spoon sampler during the performance of the Standard Penetration Test (SPT). Borehole drilling was done with a Cathead-rotary drilling machine with a wash-boring technique and the SPT, making all the obtained samples completely disturbed.

When rock formations were met, the holes were investigated using rotary diamond drilling. Bedrock was confirmed by drilling three (3) meters more into the hard strata or at maximum depth of 6.00 meters, and the drilling was terminated immediately after confirming the presence of the bedrock

All tests are described:

3.1.

Standard Penetration Test (ASTM D 1586) Done in combination with drilling at every borehole using a 50-mm O.D. split spoon sampler driven by a 63.6 kg hammer falling at 76.0cm (30 inches) whenever soil is encountered Laboratory tests were conducted on the soil samples, including grain size analysis, Atterberg limits test (plastic and liquid limits, plasticity index) and the natural moisture content (NMC) investigation. Each test was conducted according to the American Society for Testing and Materials (ASTM) standards, detailed hereafter.

3.2.

Grain Size Analysis of Soils (ASTM D 422) Soils consist of particles with various shapes and sizes. This test method is used to separate particles into size ranges and to determine quantitatively the mass of particles in each range. These data are combined to determine the particle-size distribution (gradation). The gradation of a soil is an indicator of numerous engineering properties. Hydraulic conductivity, compressibility, and shear strength are related to the gradation of the soil. Gradation is used to classify soils for engineering purposes, since particle size influences how fast or slow water or other fluid moves through a soil. Therefore, it is vital to know the particle size distribution of soil as this gives us an insight as to what purposes the soil can be used. Particle size distribution tells us if a soil is good for foundations, drainage or easily compacted. Moreover, for fine grained soils, particle size distribution is a descriptive term referring to the proportions by dry mass of a soil distributed over specified particle-size ranges. The gradation curve generated using this method yields the amount of silt and clay size fractions present in the soil based on size definitions. Determination of the clay size fraction, which is material finer than 2 μm, is used in combination with the Plasticity Index to compute the activity, which provides an indication of the mineralogy of the clay fraction.

3.3.

Atterberg Limits Test (ASTM D 4318) The Atterberg Limits determine the water content values for which the soil will behave differently, i.e., a soil may behave like a solid, semi solid, plastic, or liquid depending on the moisture content. These test methods are used as an integral part of several engineering classification systems to characterize the fine-grained fractions of soils. The liquid limit, plastic limit, and plasticity index of soils are also used extensively, either individually or together, with other soil properties to correlate with engineering behavior such as compressibility, hydraulic conductivity (permeability), compactibility, shrink-swell, and shear strength. The liquid and plastic limits of a soil and its water content can be used to express its relative consistency or liquidity index. In addition, the plasticity index and the percentage finer than 2-μm particle size can be used to determine its activity number. Specifically, the liquid limit of soil can be used to predict the consolidation properties of soil while calculating allowable bearing capacity and settlement of foundations.

3.4.

Determination of Water (Moisture) Content (ASTM D 2216) These ASTM test methods cover the laboratory determination of the water (moisture) content by mass of soil, rock, and similar materials where the reduction in mass by drying is due to loss of water. For many materials, the moisture content is one of the most significant index properties used in establishing a correlation between soil behavior and its index properties. The water content of a material is used in expressing the phase relationships of air, water, and solids in a given volume of material. More so, moisture content tells us whether our soil in the site is near its liquid state or not. Determination of such characteristic is very crucial to consider possible phenomena like liquefaction or large settlements depending on the amount of water in site. In finegrained (cohesive) soils, the consistency of a given soil type depends on its water content. The water content of a soil, among others, is used to express the soil’s relative consistency or liquidity index.

3.5. Standard Practice for Rock Core Drilling and Sampling of Rock for Site Exploration (ASTM D2113) This method is followed to properly obtain rock core samples from drilling in both hard or soft rock. Rock cores samples are handled carefully as to refrain from altering its properties before testing. Parameters obtained from this test are the core recovery percentage which tells us how fractured the rock is and the determined water level during drilling. The barrel that will be used in the test is dependent on the soil and can be modified during the testing if insufficient results are gathered.

3.6

Borehole location plan

Figure 2. . Borehole location plan

4.

REGIONAL SITE GEOLOGY Based on the presence of both marine and terrestrial mollusks, the area of Metro Manila has been interpreted to be below sea level during the early Pleistocene (Gervacio, 1968). Intermittent volcanic eruptions from nearby caldera centers namely Laguna and Taal calderas located east and south of the metropolis, led to deposition of volcanic gravity flows which filled up the shallow basin (Catane and Arpa, 1999; Catane et al., 2005). During repose periods, volcanic sediments are reworked to form lahars and epiclastic sediments. The end of each volcanic episode is marked by soil horizon. Interbeds of tuff and re-deposited sediments each with a soil capping is typical sequence of Metro Manila deposits.

Various reports from PHIVOLCS revealed that Metropolitan Manila in general is underlain by the following lithologic types: Quaternary alluvial deposits, pyroclastic flow deposits or ignimbrites, and tuff and tuffaceous deposits. Based on stratigraphic studies, there are several units of pyroclastic flow deposits observed in Metropolitan Manila, but these do not necessarily come from a single source and from the same event. In areas adjacent to Manila, other lithologic units were also reported. These are: pyroclastic deposits from Taal Caldera which underlies the southern border of Metropolitan Manila, conglomerate units that have been observed north of Quezon City in Novaliches, old lava flows that were observed outcropping northeast of Quezon City, i.e., in Rodriguez (formerly Montalban), Rizal, and old basement complex in Rodriguez, Rizal, east of Quezon City.

Quaternary Alluvium Unconsolidated sediments underlie most part of the cities of Manila, Caloocan, Pasig, Pasay

and

Taguig.

From

borehole

data,

interbeds

of

sandstone-siltstone-

mudstone/claystone and channel-fill conglomerates with or without shell fragments are the dominant lithology. Marikina City which is situated within the Marikina Valley east of Quezon City is underlain by unconsolidated alluvial deposits composed of clay, silt and sand.

Pyroclastic Flow Deposits A pyroclastic flow deposit is a type of volcanic rock unit deposited by turbulent mixture of flowing mass of fragmental materials and hot gases that cascade down the slope of a volcano at high speed during an explosive eruption. There are at least two types of pyroclastic flow deposits underlying Metropolitan Manila. These are the, mixed scoriapumice pyroclastic flow and dominantly fine-grained pumice-rich pyroclastic flow. These pyroclastic flow deposits are associated with calderagenic eruptions of either Taal Caldera or Laguna Caldera, which are the nearest calderas to Metropolitan Manila. Based on stratigraphic analysis of outcrops, there are several units of pyroclastic flow deposits underlying Metropolitan Manila, which could come from either these sources during several different events.

Tuff and Tuffaceous Sediments There are three types of true volcanic tuff found in the UP Balara area, Quezon City. The first two tuffs consist of light gray colored fine-grained materials. They overlie the third tuff which is a coarse grained volcanic breccia or the pyroclastic flow deposit. The first tuff layer is well lithified, fine grained and in some areas dark prismatic minerals and pumice may be seen. The second tuff layer is finer grained and is composed mostly of volcanic ash. Its main characteristic is the presence of accretionary lapilli. In some places planar laminations and concentrations of sand-size scoria and pumice can be seen in this type of volcanic tuff. Reworked deposits of primary tuff and pyroclastic flow deposits are widely distributed within and around Metropolitan Manila. An example of this is seen along C-5 in Pasig City, where the pumice-scoria pyroclastic flow deposit laterally changes to laharic facies. Tuffaceous reworked deposits can also be found beneath pyroclastic flow units such as in the excavation for Valerio Towers in Makati that shows the pyroclastic flow unit to overlie a sequence of epiclastic sediments that are part marine.

Pyroclastic Deposits From Taal Caldera The southern edge of Metropolitan Manila is underlain by pyroclastic materials from Taal Caldera. The extent of Taal Caldera deposits was delineated based on geomorphologic expression on the topographic map. Topographic face shows gentle slopes

to northwards starting from Tagaytay Ridge. Very few descriptions regarding these deposits are available.

Conglomerates Conglomerates in Metropolitan Manila are usually channel-fill deposits such as those found in an outcrop along Commonwealth Avenue. The lens-shaped channel-fill conglomerates are interbedded with finer tuffaceous sediments. This deposit ranges from being matrix-supported to clast-supported and consists of pebble to cobble clasts of basaltic and andesitic rocks. Its matrix usually consists of sand-size particles with minor pumice fragments. Farther north, thicker deposits can be found in Caloocan City and Novaliches, Lagro, and Fairview areas in Quezon City.

Old Lava Flows The northeastern portion of Metropolitan Manila is underlain be metamorphosed volcanics classified as porphyritic andesite and basalt. The andesitic unit is thoroughly weathered, brecciated and faulted while the basaltic unit is epidotized and crisscrossed by numerous striations and veinlets of calcite. These old volcanics have been observed outcropping in Rodriguez, Rizal north of Quezon City.

Basement Complex The Basement Complex consist of a sequence of pillow basalts, pillow basalt breccias, reworked pillow basalts transitional to hyaloclastic sediments interbedded with laminated reddish-brown radiolarian cherts and mudstones that underlie the Sierra Madre Range. These rock types are considered older than the oldest overlying sedimentary unit in the region. The Basement Complex can be observed in the area of Cainta, Taytay and Montalban all in the Province of Rizal, east of Metropolitan Manila

Seismicity and Hazards There are five (5) major geotectonic features that can affect the study sphere, in terms of generating significant earthquakes. These are the following: (i)

Manila Trench and its related structures,

(ii)

East Luzon Trough

(iii)

Philippine Fault Zone,

(iv)

Seismic and volcanic activity from Taal Volcano Taal Volcano is an active volcanic system characterized by numerous historic violent eruptions which produced extensive volcanic deposits in the surrounding area and generated significant earthquakes in and around Metro Manila. Some of the seismic activities associated with its eruptions caused fissures and liquefaction in the coastal area of Balayan Bay

(v)

The Valley Fault System The Valley Fault System runs from the foothills of Montalban Mountains in Rizal, southerly along the western coast of Laguna de Bay, and through the eastern edges of Tagaytay Ridge. The 7-10 fault system is composed of two north-trending parallel structures dipping towards each other, where the block in between had shifted down causing the formation of the Marikina Valley. The eastern segment of the fault borders the edge of the Marikina Valley from the Antipolo and Montalban mountains. Due to its proximity, it is thought to pose the greatest threat to Metropolitan Manila.

The VFS consists of two sub-parallel faults, namely the West Valley Fault (WVF) which lies between Marikina Valley and Central Plateau, and another is the East Valley Fault (EVF) which lies between Marikina Valley and the mountains. The West Valley Fault runs from Montalban in the north, passes through east of Metropolitan Manila and west of the Laguna de Bay and extends southwards possibly as far as Tagaytay Ridge. On the east side of the Marikina Valley, the East Valley Fault, extends from San Rafael, down to Montalban south to Pasig area, then becomes a subtle tonal contrast southwards.

5.

LOCAL GEOLOGY Depth (m)

Soil Type

SPT Nvalues

Relative density/ consistency

0-1.0 1.0-2.0

SM SM

12 14

MEDIUM DENSE MEDIUM DENSE

2.0-3.0 3.0-4.0

SC SC

13 10

MEDIUM DENSE LOOSE

4.0-5.0 5.0-6.0 6.0-7.5 7.5-9.0 9.0-10.8

MH MH MH MH MH

9 11 12 14 2;2/30

LOOSE MEDIUM DENSE MEDIUM DENSE MEDIUM DENSE VERY DENSE

10.8-11.6

CH

P

11.6-13.05 13.05-15.25

CH CH

15.25-16.0

Soil Description with coarse grained with some gravel; grayish black; moist

NMC (%)

…yellowish brown to dark gray

26 37

with traces of gravel; yellowish brown to dark gray; very moist …grayish black

37 47

with traces of gravel; grayish black; very moist …with sand …with few gravel …traces of gravel

47 52 52 52 55

STIFF

with little amount of gravel; grayish black; very moist

55

9 2;2/45

STIFF HARD

…with few sand and traces of gravel; dark gray; wet …with sand

75 66

MH

P

HARD

with few sand; dark gray; very moist

66

16.0-17.5 17.5-19.0

SM SM

13 10

MEDIUM DENSE LOOSE

fine to coarse grained with traces of gravel; grayish black; very moist …black

48 80

19.0-20.5 20.5-22.0

CH CH

12 13

STIFF STIFF

with little amount of gravel; grayish black; wet

80 49

CRR (%)

22.0-23.5

CH

3

SOFT

…with portion of fine sand; dark gray

49

23.5-24.3

MH

P

SOFT

with little amount of sand and few gravel; dark gray; very moist

49 44

24.3-24.75

CH

34

DENSE

with some sand and few gravel; grayish black; very moist

24.75-26.175

SC

29:50/15

VERY DENSE

with little amount of gravel; light brown

28

26.175-27.0 27.0-28.0 28.0-29.0 29.0-30.0

Gravel Gravel Gravel Gravel

50 49 48 45

VERY DENSE VERY DENSE VERY DENSE VERY DENSE

with fine sand; subrounded rocks with portion of clay; light brown

28 0 0 0

Table 1. Summary of Borehole Logs After the boring geological survey consisting of one borehole, it was found out that at the first 4 meters of depth, sand was mostly present. At 4m to 10.8m, silt was the most dominant. At 10.8m to 15.25m clay is found. At 15.25m to 19m, both silt and sand was again present, respectively. From 19m to 24.75m, clay was again present with a little amount of gravel on top and a portion of sand and gravel at the bottom, with a small layer of silt at 24m. At 26.175 m to 30 m gravel is already a dominant component, which was assumed as the bedrock. This arrangement of soil profile is due to the interbeds of tuff and re-deposited sediments each with a soil capping, which is a typical sequence of Metro Manila deposits.

6.

ANALYSIS OF GEOTECHNICAL INFORMATION

The geotechnical properties of soils can be estimated based on correlations with the SPT resistance or the N-value. For cohesionless soils, the SPT N-value is correlated with the relative density (Dr), angle of internal friction (φ), wet unit weight (γwet) and deformation modulus (Es). For cohesive soils, the correlated properties include consistency, undrained shear strength (su), γwet and Es. For mixed soils the SPT-N value is correlated with the relative density, approximate cohesion and approximate angle of internal friction. In determining the angle of friction (φ), it is classified into the two soils: the cohesionless soils, and mixed soils. For cohesionless soils, there are two correlations, which we can choose from in correlating the N-value and the Angle of internal friction, (φ), as shown in table 3 and table 4 below:

Table 2. Correlation of SPT N60 value and friction angle for granular soils

Table 3. Correlation of SPT N-value and Approximate Angle of Internal Friction (1959 Soil Mechanics and Foundation Engineering by Wilun & Starzewski, v. 1)

In determining the cohesion, (c), it is classified into the two soils, cohesive soils or clays, and mixed soils. For cohesive soils or clays, the SPT-N value can be correlated to the approximate cohesion as shown below:

Table 4. Correlation of the SPT N-value and the cohesion (Essentials of Soil Mechanics, David F. McCarthy) Also, the cohesion can be determined with the type of the soil from from http://www.geotechdata.info/parameter/cohesion.html. In determining both the angle of friction (φ) and approximate cohesion (c) for the mixed soils, they are correlated as shown below:

Table 5. Correlation of SPT N-Value and the Approximate Cohesion (c) and Approximate Angle of Internal Friction (φ) (1959 Soil Mechanics and Foundation Engineering by Wilun & Starzewski, v. 1)

Table 6. Correlation of SPT N60 value and undrained shear strength for cohesive soils

In determining the unit weight, the SPT-N Value was also correlated with unit weight (γ) for granular soils, cohesive soils and for all soils considering the water table.

For granular soils, it is correlated as follows:

Table 7: Empirical Values for Unit Weight (γ) for granular soils based on SPT N-Value (Bowles, Foundation Analysis)

For cohesive soils, it can be correlated as follows:

Table 8: Empirical values for the unit weight (γ) of cohesive soil from the SPT N-Value (Bowles, Foundation Analysis)

Table 9. Typical values of soil index properties It should be noted that 1 pcf = 157.087 N/m3

In empirically correlating the SPT N-value, for all soils in considering the water table, with the unit weight (γ), it is shown as follows:

Table 10. Empirical Determination of Unit Weight (γ) (1959 Soil Mechanics and Foundation Engineering by Wilun & Starzewski, v. 1)

For the properties of the identified rock layers from 26.175m to 30m, these were also correlated with other geotechnical parameters. Typical allowable bearing pressures for foundations laying on different types of bedrock are presented as follows:

Table 11: . Typical allowable bearing pressures for foundations on bedrock Rock was assigned a presumptive end-bearing capacity of 3.24 MPa according to the Presumptive Bearing Capacity Values as per IS1904-1978. Rock was assumed to behave as a confined rock fill with phi’ = 38 degrees and c’ = 0. (Hoek and Brown, 1995) The summary of the geotechnical parameters correlated and used in the design of the foundations are as follows:

Depth (m)

Soil Type

0-1.0 1.0-2.0

SM SM

2.0-3.0 3.0-4.0

SC SC

4.0-5.0 5.0-6.0 6.0-7.5 7.5-9.0 9.0-10.8

MH MH MH MH MH

10.8-11.6

CH

11.6-13.05 13.0515.25

CH CH

PI

15 15 29 29 20 20 20 39 39 41 42

Angle of Friction (degrees )

Cohesion (kPa)

32

22

33

22

17.2 9.4

15

5

9.4

14

5

8.8

12

20

8.8

13 13 14

20 20 20 20

9.4 9.4 9.4

P

0

25

9

0

25

2;2/45

0

25

SPT Nvalues

12 14 13 10 9 11 12 14 2;2/30

Unit Weight (kN/m3 )

8.8

Presumptiv e Bearing Capacity

15.25-16.0

MH

16.0-17.5 17.5-19.0

SM SM

19.0-20.5 20.5-22.0

CH CH

22.0-23.5

CH

23.5-24.3

MH

24.3-24.75 24.7526.175 26.17527.0 27.0-28.0 28.0-29.0 29.0-30.0

CH

42

P

42 42 35 35 35 33 12

SC Gravel Gravel Gravel Gravel

20

13 10

18 17

22 22

12 13

0 0

25 25

3

0

25

P

9.4 8.8 9.4 9.4 7.8

20

34 29:50/1 5

0

25

11.0

5

12

50 38 0 11.8 49 38 0 11.8 48 38 0 11.8 45 38 0 11.8 Table 12 : Summary of Correlated Geotechnical Data

3.24 3.24 3.24 3.24

The angle of friction used was from table 6. The cohesion was obtained from http://www.geotechdata.info/parameter/cohesion.html. The Unit weight was obtained using Figure 11. 7.

GEOTECHNICAL RISKS

7.1

Expansive Clay

Inorganic soils with liquid limits above 50 and plasticity index (PI) above 30 are deemed to have a high risk of swelling, and moderate risk is indicated by liquid limit (LL) ranging from 25 to 50 and PI ranging from 15 to 30. Low risk soils will have LL less than 25 and PI less than 15 The Liquid Limit, Plasticity Index, and the Risk per interval of depth is tabulated as follows:

Depth (m)

Soil Type

0-1.0 1.0-2.0 2.0-3.0

SM SM SC

LL

PI

-

-

45 45

15 15

Risk

Moderate Moderate

3.0-4.0 4.0-5.0 5.0-6.0 6.0-7.5 7.5-9.0 9.0-10.8

SC MH MH MH MH MH

61 61 52 52 52 73

29 29 20 20 20 39

High Moderate Moderate Moderate High

10.8-11.6

CH

73

39

High

11.6-13.05 13.05-15.25 15.25-16.0 16.0-17.5 17.5-19.0 19.0-20.5 20.5-22.0 22.0-23.5 23.5-24.3 24.3-24.75

CH CH MH SM SM CH CH CH MH CH

75

41

79 79 75 75 68 68 68 65 39 39

42 42 42 42 35 35 35 33 12 12

High High High

High

High High High High High High

Low 24.75-26.175 SC Low 26.175-27.0 Gravel 27.0-28.0 Gravel 28.0-29.0 Gravel 29.0-30.0 Gravel Table 13. Summary of Data for Soil Expansion Risk

7.2 Liquefaction Risk The medium dense sand layers near the surface are potentially at risk of liquefaction, as these types of shallow sand layers are generally more susceptible to it. The history of seismic activity in the region is an indication that the seismic activity that could cause these layers to liquefy is likely to occur.

7.3 Ground Settlement Risk The layers of cohesive soil seen in the boreholes suggests that longer term consolidation of the soil is possible.

8.

RECOMMENDATIONS OF THE TYPE OF FOUNDATION AND THE

ASSOCIATED CAPACITIES A shallow foundation system and a deep foundation system are both presented for the choice of the client. The shallow foundation system recommended is an isolated spread footing because these are more economical than other types of footings, and bored piles are recommended if deep foundations are to be used.

8.1 Shallow Foundation For the calculation of shallow foundation bearing capacity, the Terzaghi’s Bearing Capacity Theory was used. The coefficients used in the formula were interpolated from the figure below and found using the averaged correlated internal friction angle per soil layer up to the foot of the recommended footing, which would be at a depth of 4m from the ground.

Table 14. Correlation of Angle of Friction and coefficients for Terzaghi’s Eqt The ultimate bearing capacity is, then, computed as follows:

(eqt. 1) The water table at 1.5m was a considered in the second term, specifically in q, of the Terzaghi’s Equation. The c’ and γ used are also obtained from the average of the cohesion and unit weight from the top layer up to the foot of the recommended footing, respectively. The value of the

side length, B, was varied for 2m, 2.5m and 3m. The following figures show the computation for the following side lengths. For a side length of 2m:

For a side length of 2.5m:

Lastly, for a side length of 3m:

None of the shallow foundation has satisfied the requirement of load of 3,299.079054kN per foundation. Thus, deep foundation must be used.

8.2 DEEP PILE FOUNDATION If the capacities per foundation required exceed that allowed by the shallow foundations, deep foundations become necessary. Driven Piles were used.

To compute for the unit skin friction resistance of each layer, the formula presented by Braud was used (fave= 0.224*pa*N600.29). N60 was assumed to be roughly equivalent to the SPT N-Value because of a lack of pile hammer data. The fave for each layer were computed and tabulated as shown in the following tables for different boreholes.

Depth (m)

Soil Type

Braud Suggestion (fave= 0.224*pa*N60^0.29)

0-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0 5.0-6.0 6.0-7.5 7.5-9.0 9.0-10.8 10.8-11.6 11.6-13.05 13.05-15.25 15.25-16.0 16.0-17.5 17.5-19.0 19.0-20.5 20.5-22.0 22.0-23.5 23.5-24.3 24.3-24.75 24.75-26.175 26.175-27.0 27.0-28.0 28.0-29.0 29.0-30.0

SM SM SC SC MH MH MH MH MH CH CH CH MH SM SM CH CH CH MH CH SC Gravel Gravel Gravel Gravel

77.952 90.944 84.448 64.96 58.464 71.456 77.952 90.944 97.44 58.464 58.464 64.96 90.944 84.448 64.96 77.952 84.448 19.488 90.944 220.864 188.384 324.8 318.304 311.808 292.32

Table 15. Unit Skin Friction Resistance of Each Layer in BH From the computation of the fave, the Qs was computed using

. With

varying lengths and diameters, the Qs are computed below: For Borehole:

For Qs, kN Diameter, m

0.8

1.2

1.5

1420.381897 2008.12613 2453.832174

2130.572846 3012.189196 3680.748261

2663.216057 3765.236494 4600.935326

Length, m 7.5 10 12.5

Table 16. Skin Friction Resistance in BH

In computing for the ultimate point resistance, Meyerhof (1976) suggested a correlation in granular soil with the standard penetration resistance, which is:

The N60 used in the preceding equation is the average of the N60 of the soil or rock above and below within 10*D and 5*D, (where D is the diameter of the piles) respectively. In getting Qp, qp was multiplied to the area of the piles. The values of the ultimate point resistance in kN are tabulated below: For Qp, kN Diameter, m

0.8

1.2

1.5

Length, m 7.5 10 12.5

2243.0972 3251.548 4064.435 2251.8936 4407.896 5553.887 2332.3184 5277.876 6884.506 Table 17. Point Resistance in BH

The Qtotal was obtained by adding the Qp and Qs, which is also tabulated below: For Borehole: For Qtotal, kN Diameter, m

0.8

1.2

1.5

Length, m 7.5 3663.48 5382.12 6727.65 10 4260.02 7420.09 9319.12 12.5 4786.15 8958.62 11485.4 Table 18. Total Resistance in BH The Qallowable was computed by using a factor of safety equal to 3 and dividing it to the Qtotal computed minus the weight of the pile. The Qallowable for different diameters and depths of the piles are tabulated as follows: For Borehole: For Qallowable, kN Diameter, m

0.8

1.2

1.5

Length, m 7.5 1132.43 1594.4 1930.61 10 1301.7 2207.17 2690.46 12.5 1447.5 2653.47 3308.58 Table 19. Allowable Resistance in BH

Given the following allowable resistances of the soil from the borehole, the most appropriate size for the structure can be selected from the table. Since each footing needs to carry a load of 3,299.079 kN. A pile with a diameter of 1.5m and a length of 12.5 meters must be placed in the 10 footings assigned. Also, due to high risk of expansive soils, Deep Pile Foundation is a good choice.

9.

References: 

DAS, B. M. (2018). PRINCIPLES OF FOUNDATION ENGINEERING. S.l.: CENGAGE LEARNING.



Bowles, L. E. (1996). Foundation analysis and design. McGraw-hill. Chicago California Department of Transportation. (2014, March). Caltrans Geotechnical Manual



Hoek, E., & Kaiser, P. K. (1995). Bawden. W, F, 48-56.



Johnson, R.B. and DeGraff, J.V. (1988) Principles of Engineering Geology, Wiley.



Montana

Department

Transportation

of

Transportation.

(2008).

Geotechnical

Montana

Manual.

Department

of

Montana.

http://www.dot.ca.gov/hq/esc/geotech/geo_manual/page/Soil_Correlations_Mar2013. pdf 

Sowers, 1979. Introductory Soil Mechanics and Foundations: Geotechnical Engineering, 4th Ed., Macmillan, New York. (as referenced in Coduto, 1999. Geotechnical Engineering: Principles and Practices. Prentice Hall. New Jersey.)



http://open_jicareport.jica.go.jp/pdf/12001491_02.pdf

University of the Philippines – Diliman College of Engineering

INSTITUTE OF CIVIL ENGINEERING

CE 164 Geotechnical Engineering III 1st Semester AY 2017-2018

GEOTECHNICAL ANALYSIS FOR THE CYLINDRICAL CHEMICAL TANK INSIDE THE CHEMICAL 164 FACTORY IN PANDACAN, METRO MANILA

Submitted by: Nico C. Crisostomo

Submitted to: Dr. Alexis A. Acacio Professor

Date Submitted: December 20, 2017