Lateral Pressure of Poured Concrete: Arguments from Ultra-Deep Diaphragm Wall (120 m) Construction
Round 1
Reviewer 1 Report
The proposed work focuses on the use ultra-deep underground diaphragm walls in-13 stead of formwork for conventional lateral pressure testing. It is of potential interest to applied sciences journal readers.
The originality of this paper was to provide a new idea for formwork lat-17 eral pressure with the advantages of longer casting time, higher casting height, and more casting 18 times, and provides a way for thixotropy measurement.
Despite the importance of the subject addressed, this work needs many improvements to be ready for the publication in the journal of applied sciences.
Specific points of improvement :
- Abstract is too short and very weak. It must be rewritten.
- The objective of the investigation must be more developed. It must be justified by citing more pervious researches.
- Materials and methods section must be more organized.
- Quality of figures and Tables must be improved.
- Results must be discussed in depth.
- Conclusion is too wordy. Only the main results must be presented in this section.
Author Response
- Abstract is too short and very weak. It must be rewritten.
Reply: The authors agree with the reviewer. We have rewritten the abstract of this paper as follows.
Formwork lateral pressures are critical to engineering safety, and laboratory tests are often limited by time, height, etc. Formwork lateral pressures are related to early concrete fluid behavior (e.g., thixotropy). In this paper, we propose to use ultra-deep underground diaphragm walls instead of formwork for conventional lateral pressure testing. During the construction process, three measurement points were set up in the ultra-deep diaphragm wall at -40 m, -80 m and -100 m. The concrete was divided into 22 casts and the development of lateral pressure and the effect of time on lateral pressure were observed under 22 casts, respectively. It was found that the characteristic height of all three measurement points was around 21m. The average casting speed for this test was 16.846 m/h, with the fastest speed being 32.148 m/h. The time-dependent phenomenon of rapid rise and fall of lateral pressure with each casting was observed. This method provides a new way of thinking for formwork lateral pressure with the advantages of long testing time, high casting height and many tests, not only for formwork lateral pressure but also for early age thixotropy measurement of concrete.
- The objective of the investigation must be more developed. It must be justified by citing more pervious researches.
Reply: The authors thank for the reviewer’s comments. We have reorganized the related studies on lateral pressure and cohesion and added some references.
- Materials and methods section must be more organized.
Reply: The authors agree with the reviewer. The chapter has been divided according to 2.1 materials and 2.2 Underground diaphragm wall filling test.
- Quality of figures and Tables must be improved.
Reply: The authors agree with the reviewer. We plotted the data again and updated Figures 1, 3, 4 and 5 to improve the clarity of the images. In Figure 5, the different shapes for the different trips have been changed to red dots for the pouring period and blue dots for the pouring interval.
- Results must be discussed in depth.
Reply: The authors agree with the reviewer. We have added a theory on cohesion to the discussion section, which explores on the theory of thixotropy. We have also added a discussion of the cross-sectional area in Section 4.4, and the additions are listed below.
- The thixotropic nature of concrete causes it to regain fluidity if it is stirred by external forces during the hardening process. As solidification occurs, the internal cohesion of the concrete gradually increases and the lateral pressure decreases. If the pouring is carried out again at this time, the cohesion is destroyed, the fluidity increases again, and the lateral pressure then increases. As shown in Figure VIII, the placing of concrete leads to a significant rise in lateral pressure. The effect of thixotropy lasts for about 2.5 h at all heights, after which the effect disappears. It can be concluded that thixotropy is only affected below the characteristic height during the casting process.
- The cross-sectional area of the ultra-deep diaphragm wall in this test was a constant value and did not change during the pouring process. If the cross-sectional area suddenly decreases, the pouring speed increases abruptly and the tendency of lateral pressure growth will be more obvious.
- Conclusion is too wordy. Only the main results must be presented in this section.
Reply: The authors agree with the reviewer. The conclusion section has been adjusted and the first paragraph of the section has been deleted.
Reviewer 2 Report
1. it is better to specify the units in formula 2
2. table 3 contains very non-linear lateral pressure data (-80 m and -40 m). (+, -, +) how to explain it?
3. this is a practical work with the measurement results. Theoretical part is missing
Author Response
- It is better to specify the units in formula 2.
Reply: The authors agree with the reviewer. The units of the variables in the formula have been added.
where, F is the maximum lateral pressure (kN/m2), is the unit weight of concrete(kN/m3) and h is the casting height(m).
- Table 3 contains very non-linear lateral pressure data (-80 m and -40 m). (+, -, +) how to explain it?
Reply：The authors agree with the reviewer. We have explained the existence of positive and negative values for the lateral pressure increments at the bottom of Table 3.
In Table 3, the negative value of the lateral pressure increments at the -100m measurement point caused by the fourth car casting belong to the test error and is within the allowable error range. The lateral pressure at each measurement point is positive until it reaches its peak and then appears negative. This is because each cast before reaching the peak affects the cohesion of unconsolidated concrete, reducing it again and increasing the concrete fluidity. The lateral pressure at each measurement point experiences roughly 1.5 hours from exceeding the hydrostatic pressure to the maximum lateral pressure. During this process, the concrete in the vicinity of the measurement point gradually sets and the cohesion is no longer affected by the new round of pouring. At the same time, as the time grows, the degree of setting increases and the fluidity of the concrete decreases, so the lateral pressure increment appears negative. If the interval between two casts is short, there will also be a slightly positive value of the lateral pressure increment.
- This is a practical work with the measurement results. Theoretical part is missing.
Reply: The authors agree with the reviewer. We have added a theory on cohesion to the discussion section, which explores on the theory of thixotropy.
The thixotropic nature of concrete causes it to regain fluidity if it is stirred by external forces during the hardening process. As solidification occurs, the internal cohesion of the concrete gradually increases and the lateral pressure decreases. If the pouring is carried out again at this time, the cohesion is destroyed, the fluidity increases again, and the lateral pressure then increases. As shown in Figure VIII, the placing of concrete leads to a significant rise in lateral pressure. The effect of thixotropy lasts for about 2.5 h at all heights, after which the effect disappears. It can be concluded that thixotropy is only affected below the characteristic height during the casting process.
Reviewer 3 Report
Dear authors,
please find my opinions on the article, including specific comments. As such, I consider the research to be good, the article is well readable, however, it can be improved for the reasons listed below.
A brief summary
The article deals with the development of lateral pressure in concrete during the time between pouring and solidification of the concrete mixture. The case study is applied to a relatively massive structure (with a large height/depth of concreting). These constructions require research in the given area to achieve concreting efficiency, time efficiency, associated with the possible elimination of used chemical additives. For these reasons, I consider the article topically current and relevant. In the Article, however, I am missing some data on the concrete used and partial tests such as the slump/flow.
General concept comments
The abstract should provide some of the main results and specific conclusions based on them.
The introduction section of the article provides a clear literature review.
The methodology is not visibly presented (as a separate chapter), but hidden in Chapter 2. The work methodology is clear except for small details. The results are clear and supported by diagrams and tables, but some of the images and graphs are of low quality.
Specific comments
Line 83-91: The specification of the cement is given, however it would be appropriate to give the specification of the concrete mixture as well as of some of its properties in the fresh state. I miss concrete in situ testing like slump (flow) test.
To what degree of exposure class (EC) is the structure designed?
Did EC affect the admixtures (as stated in the introduction) to the concrete, which could affect the development of internal forces during and immediately after casting?
What aggregate (aggregate particle size) for concrete was chosen if it affects the lateral pressure?
What is the water-cement ratio of the concrete used?
Line 126-140: The equation and associated text do not contain units for each quantity (variable).
Table 3: It would be appropriate to explain in the text the reasons for the negative values of lateral pressure increments, given in the table 3.
Figure 5: The real legibility of the point marks for individual "casts" (19 in total) is very small. The difference between the individual point markers (small triangles rotated differently) is unreadable due to the low quality of the image and the density of the graph. It is unnecessary to distinguish individual "casts" with a point mark if the aim of the image is to show the trend only. If the goal of the picture is to consider the dependence also on the number of "casts" performed, then I would distinguish each individual "cast" by colour.
Discussion section: It would also be appropriate to investigate whether not only the speed of concreting, but also the cross-section of the concreted structure (massiveness) influences the development of lateral pressure.
Overall Recommendation
Accept after minor revision (corrections to minor methodological errors and text editing).
I wish the authors continued research success.
Kind Regards.
Author Response
- Line 83-91: The specification of the cement is given, however it would be appropriate to give the specification of the concrete mixture as well as of some of its properties in the fresh state. I miss concrete in situ testing like slump (flow) test.
Reply: The authors agree with the reviewer. We added the value of concrete slump.
The slump of the concrete was 240 mm.
- To what degree of exposure class (EC) is the structure designed?
Reply: The authors thank for the reviewer’s comments. This structure is an underground diaphragm wall, which is a temporary support structure for underground works. The underground diaphragm wall in the upper 20m depth range is combined with the future lining wall as the outer wall of the box foundation. So the material design is not concerned with the exposure level.
- Did EC affect the admixtures (as stated in the introduction) to the concrete, which could affect the development of internal forces during and immediately after casting?
Reply: The authors thank for the reviewer’s comments. Because the structure did not consider the effect of exposure conditions, the admixtures were selected without considering the effect of exposure environment.
- What aggregate (aggregate particle size) for concrete was chosen if it affects the lateral pressure?
Reply: The authors agree with the reviewer. We added the particle size of the aggregates and the type of admixture in section 2.2.
The particle size of round aggregates was 30mm. The admixture used in the test is the third generation of polycarboxylic acid water reducing agent.
- What is the water-cement ratio of the concrete used?
Reply: The authors thank for the reviewer’s comments. As shown in Table 1, W/B is the water-binder ratio, i.e., the ratio of water to cement, fly ash, and slag. The water-cement ratio mentioned by the reviewer can be obtained from the volume of water and cement in the table.
- Line 126-140: The equation and associated text do not contain units for each quantity (variable).
Reply: The authors thank for the reviewer’s help. The units of the variables in the formula have been added.
where t is the flow time of concrete in the pipe(s), ti is concrete casting time for the i-th concrete tanker(s), r is pipe inner diameter (0.15m), l is the casting length of the same length as the instrument position(m), Q is the concrete capacity of pipeline within flow length(m3), Qi is the capacity of the i-th concrete tanker(m3), and v is the average flow velocity of concrete is considered according to the casting velocity when the place is submerged by concrete(m/s).
- Table 3: It would be appropriate to explain in the text the reasons for the negative values of lateral pressure increments, given in the table 3.
Reply：The authors agree with the reviewer. We have explained the existence of positive and negative values for the lateral pressure increments at the bottom of Table 3.
In Table 3, the negative value of the lateral pressure increments at the -100m measurement point caused by the fourth car casting belong to the test error and is within the allowable error range. The lateral pressure at each measurement point is positive until it reaches its peak and then appears negative. This is because each cast before reaching the peak affects the cohesion of unconsolidated concrete, reducing it again and increasing the concrete fluidity. The lateral pressure at each measurement point experiences roughly 1.5 hours from exceeding the hydrostatic pressure to the maximum lateral pressure. During this process, the concrete in the vicinity of the measurement point gradually sets and the cohesion is no longer affected by the new round of pouring. At the same time, as the time grows, the degree of setting increases and the fluidity of the concrete decreases, so the lateral pressure increment appears negative. If the interval between two casts is short, there will also be a slightly positive value of the lateral pressure increment.
- Figure 5: The real legibility of the point marks for individual "casts" (19 in total) is very small. The difference between the individual point markers (small triangles rotated differently) is unreadable due to the low quality of the image and the density of the graph. It is unnecessary to distinguish individual "casts" with a point mark if the aim of the image is to show the trend only. If the goal of the picture is to consider the dependence also on the number of "casts" performed, then I would distinguish each individual "cast" by colour.
Reply: The authors agree with the reviewer. We have changed all the casting periods to be indicated by red dots and the pouring intervals to be indicated by blue dots in Figure 5.
- Discussion section: It would also be appropriate to investigate whether not only the speed of concreting, but also the cross-section of the concreted structure (massiveness) influences the development of lateral pressure.
Reply: The authors agree with the reviewer. We have added a discussion of the cross-sectional area in Section 4.4, and the additions are listed below.
The cross-sectional area of the ultra-deep diaphragm wall in this test was a constant value and did not change during the pouring process. If the cross-sectional area suddenly decreases, the pouring speed increases abruptly and the tendency of lateral pressure growth will be more obvious.
Reviewer 4 Report
The submitted paper presents a study on lateral pressure of poured concrete — arguments from ultra-2 deep diaphragm wall (120m) construction.
The manuscript is written well, has no technical errors, easy to read, and is understandable. Overall, this paper can be accepted for the Journal of Applied Sciences after the authors make some improvements to the manuscript as follows:
1. Figure 1 should be illustrated in three dimensions so that all sizes of the diaphragm wall can be seen clearly.
2. It is not explained why the lateral pressure (at each measured depth of 40, 80, and 100m) shown in Figures 3 and 4 increases and decreases suddenly.
Author Response
- Figure 1 should be illustrated in three dimensions so that all sizes of the diaphragm wall can be seen clearly.
Reply: The authors agree with the reviewer. We added Figure 1(b) to illustrate the distribution of measurement points in the Z-axis direction, because the length of the Z-axis direction is much larger than that of the X-axis and Y-axis, and it is not convenient to draw a three-dimensional diagram to represent it.
- It is not explained why the lateral pressure (at each measured depth of 40, 80, and 100m) shown in Figures 3 and 4 increases and decreases suddenly.
Reply：The authors agree with the reviewer. We have explained the existence of positive and negative values for the lateral pressure increments at the bottom of Table 3.
In Table 3, the negative value of the lateral pressure increments at the -100m measurement point caused by the fourth car casting belong to the test error and is within the allowable error range. The lateral pressure at each measurement point is positive until it reaches its peak and then appears negative. This is because each cast before reaching the peak affects the cohesion of unconsolidated concrete, reducing it again and increasing the concrete fluidity. The lateral pressure at each measurement point experiences roughly 1.5 hours from exceeding the hydrostatic pressure to the maximum lateral pressure. During this process, the concrete in the vicinity of the measurement point gradually sets and the cohesion is no longer affected by the new round of pouring. At the same time, as the time grows, the degree of setting increases and the fluidity of the concrete decreases, so the lateral pressure increment appears negative. If the interval between two casts is short, there will also be a slightly positive value of the lateral pressure increment.
Round 2
Reviewer 1 Report
I think that the revised version of the submitted paper is well improved by considering the reviewers and editor recommendations and remarks. Indeed, I think that this paper is accepted in this form
