NEED HELP UNDERSTANDING IBC CLAUSE (EXPANSIVE SOIL) 1

[Tstruct]

Hello everyone,
Please have a look at the attached image of IBC 2021 clause.
I have the following doubts:
It says all four criteria need to be fulfilled for a soil to be expansive whereas it also says if test mentioned in point 4 is conducted then points 1,2 & 3 not required to be fulfilled. What does it mean? Isn't there a contradiction in the statement? It is saying to meet all four points, but also saying if point 4 is conducted point 1,2 & 3 are not required. How should I proceed?

Thanks.

 

[HTURKAK]

Point 4 literally means Expansion Index test is compulsory and if > 20 sufficient condition by itself. My interpretation of the clause 1803.5.3 is , conduct expansion index test. If Expansion Index > 20 , no need to look the other tests. The soil is expansive. If less Expansion Index is less then 20, then conduct also the other test to decide if soil is expansive ( 1,2,3) .

The following para. copy and paste from IBC Handbook Illustrated .

1803.5.3 Expansive soil. Expansive soils are those that shrink and swell appreciably because of changes in soil moisture content. Reference should be made to Section 1808.6 for mitigation methods and design for expansive soils. Frost heave is not considered in this section. Expansive soils are present or prevalent in all 50 states of the United States and in many other countries around the globe. Soils must meet all four of the criteria to be classified as expansive, not just a high Plasticity or Expansion Index. The section allows two different ways to identify expansive soils. The first option involves meeting four criteria: (1) Plasticity Index (PI) of 15 or greater determined by ASTM D 4318; (2) more than 10 percent of the soil particles pass a No. 200 sieve determined by ASTM D 422; (3) more than 10 percent of the soil particles are less than 5 micrometers in size as determined by ASTM D 422; and (4) an Expansion Index greater than 20 according to ASTM D 4892. The second option is to determine if the Expansion Index (according to ASTM D 4892) is greater than 20. If the Expansion Index is
determined, the first three tests need not be conducted. In other words, Expansion Index > 20 is both a necessary and sufficient condition by itself.

 

[MintJulep]

It's badly written.

As written, of the soil meets the conditions of items 1, 2 and 3, but item 4 returns less than 20 it's not expansive.

So, why did you need to do 1, 2 and 3?

=OR(AND(A, B, C, D), D)

 

[Tstruct]

Thank you @HTURKAK and @MintJulep
@HTURKAK I don't understand why code committee has introduced point 1,2 and 3 when result solely depends on point 4 (Expansion index). In UBC 97, there was only one criteria for a soil to be expansive that is expansion index only.

 

[MintJulep]

I don't understand why code committee has introduced point 1,2 and 3 when result solely depends on point 4

Debating it on the internet won't answer nor solve the problem. There must be a way to submit questions and comments to the IBC committee. Start here: https://www.iccsafe.org/about/contact-icc/

You can read past versions of the IBC here: https://codes.iccsafe.org/codes/i-codes

The current language of 1803.5.3 was introduced in 2009 and has not changed since then.

Unfortunately the earliest available revision histories are for the 2012 version (available with a subscription).

 

[Tstruct]

@MinthJulep Respectfully, I addressed @HTURKAK in my comment. Still your point is somehow valid, if you have their membership, can you please send the query on my behalf? I don't have the membership. And this forum is a place to discuss issues with experienced engineers, if someone already know the answer that would be really great and saving of time.

 

[HTURKAK]

@HTURKAK I don't understand why code committee has introduced point 1,2 and 3 when result solely depends on point 4 (Expansion index). In UBC 97, there was only one criteria for a soil to be expansive that is expansion index only.

- Expansive soil does not depend on solely Point 4 . If Expansion Index greater than 20 , it is sufficient condition by itself and no need to conduct tests 1,2,3.
- When you conduct point 4 test and If Expansion Index less than 20 ,it is necessary to conduct the other tests to decide if the soil is expansive.

English is not my first language but apparently IMO, the wording is bad and should be changed.

 

[MintJulep]

I am not an expert in soils. @HTURKAK's interpretation of the intent is possibly correct.

I am a native English speaker, and experienced specification writer. As written, 1803.5.3 does not match @HTURKAK's interpretation.

As a specification writer, my interest in discussions like this one is with understanding how readers understand specifications and standards, and how writers create confusing and ambiguous requirements; so that I can improve my work.

I have no direct interest in the IBC, and thus no motivation to contact IBC on this matter.

It should not be necessary to be a "member" of anything for you to submit a question or request for clarification.

 

[MintJulep]

- Expansive soil does not depend on solely Point 4 . If Expansion Index greater than 20 , it is sufficient condition by itself and no need to conduct tests 1,2,3.
- When you conduct point 4 test and If Expansion Index less than 20 ,it is necessary to conduct the other tests to decide if the soil is expansive.

English is not my first language but apparently IMO, the wording is bad and should be changed.

Well native English speaker or not, you did a better job of making it clear in three simple sentences than the committee did with five complicated sentences!

 

[Tstruct]

Thank you again both of you guys.

 

[HTURKAK]

Well native English speaker or not, you did a better job of making it clear in three simple sentences than the committee did with five complicated sentences!

I do not look to the forum every time. I just want to remind that the problems in civil engineering ( specially soil mechanics ) are not simply black or white . There are grey zones which the use of engineering judgement and experience is necessary.
For this case , if one looks to the limits ;
- For EXPANSION INDEX,

• 0 – 20: Very low.
• 21 – 50: Low.
• 51 – 90: Medium.
• 91 – 130: High.
• > 130: Very high.

- And for Plasticity index the limits are

• Low PI (e.g., <7) indicates slightly plastic soil.
• Medium PI (7-17) suggests moderate plasticity.
• High PI (>17) indicates highly plastic soil.

If the expansion index EI= 90, no need to further evidence to decide and it is clear thta the soil is expansive and if EI =10 it is also clear that the soil is not expansive . But if EI= around 20 you need to look further evidences and conduct the other 3 tests.

Just by curiosity : You are saying that you are a native English speaker, and experienced specification writer. What should be the correct wording in this case ?

 

[Ron247]

What HTURKAK noted is my understanding also.

I saw an early copy of the next code. The end of Section 1803.5.3 now reads, "To properly interpret this section, see HTURKAK".