Anyone familiar with Cliq software

[JoyceBCD]

I have a quick question about Cliq.

When you use Cliq to do liquefaction analysis, you need to input the in-situ groundwater level and the groundwater level during earthquake.

So the in-situ groundwater level normally we will use whatever we got from the site investigation, that's easy. But I am a little bit confused about what groundwater level during earthquake. what number should I use? I knew some consultant companies they just use the same number as the in-situ groundwater level. But I think this is not correct, because the groundwater table is intend to rise during earthquake. But however it is very difficult to predict how much the groundwater level going to rise during earthquake.

So is anyone has some idea about this? Or is there any paper talked about that?

Any help will be much appreciated.

Thanks.

 

[JoyceBCD]

I've seen quite a few companies using n+1 for the groundwater table after earthquake.

Which means the groundwater table rose about a meter after earthquake.

Hope that helps. Personally I think this should a conservative approach, because I don't believe in many cases that groundwater table will be able to rise a meter during earthquake.

 

[moe333]

Insitu groundwater is used to calculate soil resistance (CRR).
groundwater level during earthquake allows you to model a different groundwater level (and EQ demand) such as the max. historical groundwater level, which some agencies require. The EQ does not cause a rise in groundwater.

 

[JoyceBCD]

hi moe333,

thanks for your reply. I knew what the insitu groundwater level is used for, my question was how to determine the in-situ groundwater level during earthquake.

Can't agree with your that EQ does not cause a rise in groundwater, unless you are talking about permanent rise. But during earthquake, the Oscillations of groundwater level has been known for decades. Which means the groundwater level do rise during earthquake. Also I think you used the max. historical groundwater level as the in-situ groundwater during earthquake maybe still not appropriate, since if there is no historical earthquake, then the max. historical groundwater level might still be lower than the in-situ groundwater level during earthquake. Therefore the design carried out by using the max. historical groundwater level may be under designed.

 

[L0k]

Hi Joyce
I think the gwl during earthquake should be closed to the ground surface. The higher the gwl gives the lower effective stress as well to create the liquefaction happening or not.

 

[JoyceBCD]

hi L0k,

thanks for your reply. I was think the same thing as you when I was first using this program, but now I think that's a very conservative approach. Because, if the nature groundwater level is about 2-3m below the existing ground level you might still be right. but how about the nature groundwater level is more than 10m, 20m deep? I don't think the groundwater level can rise up all the way to the ground surface.

As I explained above, I saw some company use n+1 meter for the insitu groundwater level during earthquake, just wondering whether that's correct, and if anybody knows any paper talks about that. Many thanks.

 

[moe333]

Joyce,
I think you misunderstood my comments.
I understand that groundwater levels (generally increased porewater pressures) can rise during liquefaction, but the simplified liquefaction triggering analysis does not directly account for this dynamic, short term condition. The simplified liquefaction triggering analysis modeled with Cliq simply compares the soil strength (CRR) with the EQ demand (CSR). The G.W.T. (earthquake) in Cliq is most commonly used to model a future static groundwater level such as the Historical High groundwater level at a location. Using a higher GWT will result in a higher CSR and lower FS for liquefaction triggering. I do not believe G.W.T. (earthquake) in Cliq is intended to model the short-term dynamic rise in groundwater due to the EQ (generally increased porewater pressures) . Many agencies require consultants to use the Historical High groundwater level in liquefaction analysis since the GWT changes with time and the measured GWT during drilling may not be at the highest level. It also allows you to model the GWT if a Fill is being used.

I have pasted the definitions of these CLiq parameters from the CLiq manual below. You can also email the developer and he is generally very willing to discuss the intended use of the software parameters.

G.W.T. (insitu): This field holds the absolute depth of water level relative to the ground surface (e.g. a value of 1.00 meter means that ground water level is located one (1) meter below the ground free surface). The value of the insitu G.W.T. will be used for the determination of in-situ stresses needed for the calculation of the basic CPT interpretation and Cyclic Resistance Ratio.

G.W.T. (earthquake): This field holds the depth of water level during the earthquake and it will be used for the calculation of the Cyclic Stress Ratio (CSR). When a fill is present G.W.T. during earthquake measures from top of the fill. This means that if the insitu G.W.T. is at 2.00 meters and you place a fill of 1.50 meter height then to preserve the G.W.T. during earthquake in the same level you must enter a value of 2.00 + 1.50 = 3.50 meters.

 

[L0k]

Hi Joyce, when I read the liquefaction cases, mostly in sandy layer and closes to beach, it means the water level is quite high. Silt/fine sand pushed through the cracking ground along with water. So, in my opinion the gwl below 10m is not susceptible against liquefaction.

 

[JoyceBCD]

hi moe333,

Thanks for your reply, sorry for the misunderstanding.

I was been told that the Cliq program can capture the dynamic rise in groundwater due to the EQ, that's why I got confused.

Thanks for your explanation, and I think it sounds more reasonable.

Thanks.

 

[JoyceBCD]

hi L0K,

liquefaction is likely to happen in saturated fine SAND/SILT material, not necessary close to beach and sometimes the in-situ groundwater level is pretty low, so I still can't be convinced that the groundwater level will be increased to surface during EQ.

Thanks for your help.