# Deformation Study of Strongly Structured Clays Considering Damage Effects
## 3 Test Results and Analysis
### The Compressive Characteristics of Structurally Strong Clay at Different Disturbance Levels  
To clearly illustrate the compressive characteristics of the soil during the disturbance process, samples with disturbance degrees of \(D\) = 10.4%, \(D\) = 38.6%, \(D\) = 45.3%, \(D\) = 62.3%, and \(D\) = 100% were selected. The relationships between the compression coefficient \(a_{v}\), compressive modulus \(E_{s}\), and pressure \(P\) are presented in Figure 3, along with the relationships between the compression coefficient \(a_{v}\), compressive modulus \(E_{s}\), and damage degree \(W\) in Figure 4.  
Figure 3: Variation in compression parameters with overburden pressure for different disturbance degrees. (**a**) The relationship between the compression coefficient \(a_{v}\) and pressure \(P\) for samples with five different disturbance degrees. (**b**) The relationship between the compressive modulus \(E_{s}\) and pressure \(P\) for samples with five different disturbance degrees. Figure 2: The evolution law of the change in damage degree \(\Delta W\) with pressure \(P\). (**a**) The relationship between the disturbance degree \(\Delta W\) and pressure \(P\) for three types of disturbed samples. (**b**) The relationship between \(\Delta W\) and pressure \(P\) for samples with a disturbance degree of 38.6%. From Figure 3a, it is evident that the compression coefficients of undisturbed and remolded soil samples exhibited different trends. The compression coefficient of the undisturbed soil sample was relatively low under lower overburden pressures. As the overburden pressure increased, the void ratio decreased more rapidly, leading to a gradual increase in the compression coefficient, which reached a peak value before decreasing due to structural effects. Once the pressure exceeded a certain threshold, the compression coefficients of the undisturbed soil samples converged with those of the remolded soil samples. In contrast, the compression coefficient of the remolded soil samples was initially higher but gradually decreased as the pressure increased. Figure 3b illustrates the variation in the compressive modulus \(E_{s}\) with pressure \(P\) for samples with different disturbance degrees. The compressive modulus of the structurally strong clay from Zhanjiang can be divided into two stages as the overburden pressure increased:  
* Rapid growth stage:  
In the pressure range of 0 to 1288 kPa, the compressive modulus of the samples increased rapidly with pressure. For instance, for the sample with \(D\) = 100%, the compressive modulus rose from an initial value of 0.334 MPa to 14.7 MPa. At a pressure of 1288 kPa, all samples exhibited the same compressive modulus of 14.7 MPa. However, the sample with \(D\) = 10.4% behaved differently, showing a trend of initially decreasing and then increasing compressive modulus during the early compression phase. This behavior occurred because, when the overburden pressure was significantly lower than the structural yield stress, the undisturbed soil sample maintained its structure well, exhibiting strong resistance to deformation and making it less susceptible to compression. This resistance was closely related to the disturbance degree, gradually decreasing as the disturbance degree increased. Under the same pressure, samples with lower disturbance degrees had higher compressive moduli than those with higher disturbance degrees. * Stable growth stage:  
In the pressure range of 1288 to 3200 kPa, the compressive modulus of the samples showed a consistent growth trend. Within this pressure range, the soil experienced the gradual destruction of the cemented structure formed during natural deposition as pressure increased, leading to a gradual loss of structural integrity. Consequently, the compressive moduli of samples with different disturbance degrees approached that of the remolded  
Figure 4: Variation in compression-related parameters with the damage degree of samples with different disturbance degrees.