hi..first you tell me why did you apply the load more than 300 % as compared to the actual load. The reasons for exponential increase in settlement due to many reasons such as soil parameters, magnitude of load and failure theory used to define the behaviour of soils. the second point the dimensions and density of the mesh used for the analysis..give answers to all these details including the type of foundation etc..ok all the best..

Hi, Sir Karthigeyan . S .

As I am trying to simulate the actual static load test, I applied the loads according to the test that was done on site, hence reaching 300% of the actual load to test the pile to ultimate state. The point is to obtain a settlement that is close to the actual values so that the soil parameters can be used to simulate a rapid load test.

For soil parameters wise, the input parameters are based on the SPT-N value of the nearest borelog and also from a geotechnical baseline report. As it is a Static Pile Load Test, I modeled a single pile in axisymmetry using the Mohr Coulomb soil model in drained condition.

The model is 45m wide and 51m deep. The density of the mesh is medium, with 0.15 coarseness factor within the pile and 0.5 coarseness factor around the pile.

Thank you.

hi...have you used volume element or embedded bean to simulate the pile..you check whether the settlement before reaching exponential increase is within 10 % variation as compared to actual value. If percentage difference is within the acceptable limit mean then the exponential increase in settlement is because of the load applied higher than the actual load. I suggest you to apply the load is 1.5 times more than the actual load..also you try to check material properties of soils..ok all the best..

Hi, Sir Karthigeyan . S .

The pile is simulated as a soil body with a dummy pile at the centre.

As for the settlement increase, the exponential increase has already started at 1.5 times of actual loading and have already exceeded 10% variation. I think I would have to check the material properties.

Any advice on what to take note in the material properties to improve the accuracy of settlement analysis?

Thank you.

Hi,

Since you are simulating the actual test data (known values) to reverify or parametric study, first task is looking at the ground model and theiengineering parameters & 2nd-Pile properties as mentioned by Dr. Karthigeyan in the previous response 3rd increasing the number of steps and chencking the displacement in Plaxis w.r.t. to actual site settlement.

hi..it seems you have used volume element to simulate the pile and mesh dimension is 41 m x 41 m x 51 m. now, you tell me what is the dimension of actual pile and the model pile in your analysis with mentioning the type of pile material. Now, you have to ensure the soil properties are correct or not mainly to check Young's modulus, Poisson's ratio, unit weight of soil and shear parameters c and phi..also, the drainage conditions etc..also to check the interface parameters is correct or not..you have to make interface factor Rf as 1 for pile and 0.67 for soil..ok all the best..

Hi Sir Suresh Kumar Gupta Pasupula .

Sure, I will try to do give it a go after changing the interface factor as per Dr. Karthigeyan's comments. As my engineering parameters are taken from a baseline report, do you have any recommendations on how to optimise the parameters to be more specific?

Thank you.

Hi Sir Karthigeyan . S .

The actual pile is a reinforced concrete bored pile with a diameter of 1.5m and length of 41.6 m. For the model, I have modeled it as a linear elastic, non-porous material and axisxymmetrical with a 0.75m dia and length of 41.6m.

How do I check if my soil properties are correct? For the current input, the Young's Modulus is based on the SPT-N value, the Poisson's Ratio is set at 0.3 for all soil types and the rest of the parameters is based on the recommended values from a baseline report for the type of geological formation.

As the test is a Static load test, all drainage condition is set as drained. I will change the interface parameters and try again.

Thank you.

Hi Alvin,

The boundary spacing from pile center/pile tip is less. For example: the distance between bottom boundary and pile tip is only 9.4 m. This maybe the cause of exponential increase in settlement. Please increase this value and observe the result. Go for 0.7 times of pile length. Side boundary distances are fine.

Thanks.